''Nannochloropsis'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
alga
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...
e comprising six known
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
. The
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
in the current
taxonomic classification
In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
was first termed by Hibberd (1981).
The species have mostly been known from the marine environment but also occur in fresh and brackish water.
All of the species are small, nonmotile spheres which do not express any distinct morphological features that can be distinguished by either
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
or
electron microscopy
An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...
. The characterisation is mostly done by
rbcL gene and
18S rRNA 18S may refer to:
*18S ribosomal RNA
*18S rRNA (adenine1779-N6/adenine1780-N6)-dimethyltransferase
*18SEH
The Family II is a straight-4 piston engine that was originally developed by Opel in the 1970s, debuting in 1979. Available in a wide ran ...
sequence analysis.
The algae of the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Nannochloropsis'' differ from other related
microalgae
Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular species which exist indiv ...
in that they have ''
chlorophyll a'' and completely lack ''
chlorophyll b
}
Chlorophyll ''b'' is a form of chlorophyll. Chlorophyll ''b'' helps in photosynthesis by absorbing light energy. It is more soluble than chlorophyll ''a'' in polar solvents because of its carbonyl group. Its color is green, and it primarily ...
'' and ''
chlorophyll c
Chlorophyll ''c'' is a form of chlorophyll found in certain marine algae, including the photosynthetic Chromista (e.g. diatoms and brown algae) and dinoflagellates.
It has a blue-green color and is an accessory pigment, particularly significant ...
''. In addition they are able to build up a high concentrations of a range of pigments such as
astaxanthin
Astaxanthin is a keto- carotenoid within a group of chemical compounds known as terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups. It is a lipid-soluble pigment with r ...
,
zeaxanthin
Zeaxanthin is one of the most common carotenoids in nature, and is used in the xanthophyll cycle. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika (made from bell peppers), corn, saffron, goji ( wolfberries), ...
and
canthaxanthin
Canthaxanthin is a keto-carotenoid pigment widely distributed in nature. Carotenoids belong to a larger class of phytochemicals known as terpenoids. The chemical formula of canthaxanthin is C40H52O2. It was first isolated in edible mushrooms. It ...
.
They have a diameter of about 2 to 3 micrometers
and a very simple
ultrastructure
Ultrastructure (or ultra-structure) is the architecture of cells and biomaterials that is visible at higher magnifications than found on a standard optical light microscope. This traditionally meant the resolution and magnification range of a co ...
with reduced structural elements compared to neighbouring taxa.
''Nannochloropsis'' is considered a promising alga for industrial applications because of its ability to accumulate high levels of
polyunsaturated fatty acids
Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic proper ...
.
Moreover, it shows promising features that can allow
genetic manipulation
Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of technologies used to change the genetic makeup of cells, including t ...
aimed at the genetic improvement of the current oleaginous
strains. Various species of ''Nannochloropsis'' indeed are
transfectable and there has been evidence that some strains are able to perform homologous recombination.
At the moment it is mainly used as an energy-rich food source for fish larvae and
rotifer
The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals.
They were first described by Rev. John H ...
s. Nevertheless, it has raised growing interest also for the investigation of
biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
production from
photosynthetic organisms. (see
Nannochloropsis and biofuels
''Nannochloropsis'' is a genus of alga within the heterokont line of eukaryotes, that is being investigated for biofuel production. One marine ''Nannochloropsis'' species has been shown to be suitable for algal biofuel production due to its ease ...
). ''Nannochloropsis'' is actually in use as
food additive
Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), salt (salt ...
for human nutrition and it is also served at Restaurant "A Poniente" of
El Puerto de Santa María
EL, El or el may refer to:
Religion
* El (deity), a Semitic word for "God"
People
* EL (rapper) (born 1983), stage name of Elorm Adablah, a Ghanaian rapper and sound engineer
* El DeBarge, music artist
* El Franco Lee (1949–2016), American po ...
(
Cádiz
Cádiz (, , ) is a city and port in southwestern Spain. It is the capital of the Province of Cádiz, one of eight that make up the autonomous community of Andalusia.
Cádiz, one of the oldest continuously inhabited cities in Western Europe, ...
,
Spain
, image_flag = Bandera de España.svg
, image_coat = Escudo de España (mazonado).svg
, national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond")
, national_anthem = (English: "Royal March")
, i ...
) close to the natural environment where ''Nannochloropsis gaditana'' was first isolated and still grows.
A 2020 study suggests it could be used for a highly performant,
sustainable
Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livin ...
fish-free
feed for farmed fish.
Species
The species currently recognised are:
* ''
Nannochloropsis australis''
Fawley, Jameson & Fawley 2015
* ''
Nannochloropsis gaditana''
Lubián 1982
* ''
Nannochloropsis granulata''
Karlson & Potter 1996
* ''
Nannochloropsis limnetica''
Krienitz et al. 2000
* ''
Nannochloropsis oceanica''
Suda & Miyashita 2002
* ''
Nannochloropsis oculata''
(Droop 1955) Hibberd 1981
* ''
Nannochloropsis salina''
Hibberd 1981
Sequenced genomes
The scientific community has obtained the
genomic sequence
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gen ...
of different
strains of ''Nannochloropsis'' belonging to two
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
: ''N. gaditana''
and ''N. oceanica''.
genome portalbased on th
''N. gaditana'' B-31genome allows accessing much of the genomic information that concerns this
micro-organism
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
, moreover dedicated web pages are also available for the genomes o
''N. gaditana'' CCMP526an
The
genomes
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gen ...
of the sequenced ''Nannochloropsis''
strains were between 28.5 and 29 Mega bases long, they had high density of
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s, reduced
intron
An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e. a region inside a gene."The notion of the cistron .e., gene. ...
content, short intergenic regions
and very limited presence of repetitive sequences.
The genes of the two
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
share extended similarity.
The analysis of the
genomes
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gen ...
revealed that these
microalgae
Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular species which exist indiv ...
have set of
genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
for the synthesis and incorporation in the
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
of
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
and sulfated fucans and that they are able to store carbon in polymers of β-1,3- and β-1,6-linked glucose called
chrysolaminarin
Chrysolaminarin is a linear polymer of β(1→3) and β(1→6) linked glucose units in a ratio of 11:1. It used to be known as leucosin.
Function
Chrysolaminarin is a storage polysaccharide typically found in photosynthetic heterokonts. It is ...
.
An
NMR
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...
analysis of whole algal cells which were cultivated in
autotrophic growth reports evidence of the presence of
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
in the
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
and of mobile chrysolaminarin, probably accumulated in solution in
vacuoles
A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...
inside the cell.
Comparison between the
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
metabolic genes of ''N. gaditana'' and of
red
Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
/
green
Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...
/
brown algae
Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and po ...
and
diatoms
A diatom (New Latin, Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group com ...
provided some insights into the exemplary lipid production of ''Nannochloropsis'' cultures. The comparisons indeed highlighted the presence of an expanded repertoire of some of the
genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
involved in
TAG assembly in ''Nannochloropsis''.
Numerous
TAG lipases, which can affect
TAG metabolism through either
TAG degradation or
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
remodeling, were identified in ''Nannochloropsis'',
many of them belonging to a
gene family
A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. One such family are the genes for human hemoglobin subunits; the ten genes are in two clusters on ...
which seems to be exclusive of ''Nannochloropsis''.
[Elisa Corteggiani Carpinelli e Nicola Vitulo Unpublished data available through th]
''Nannochloropsis gaditana genome portal''
Analysis of the genomic data suggested the presence in both the two
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of ''Nannochloropsis'' of
regulatory RNA
RNA interference (RNAi) is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. Historically, RNAi was known by o ...
and in particular
miRNA
MicroRNA (miRNA) are small, single-stranded, non-coding RNA molecules containing 21 to 23 nucleotides. Found in plants, animals and some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. miRN ...
.
Various
orthologs
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a spec ...
of known blue light sensing proteins were found in the genomes of ''Nannochloropsis'' suggesting possible
circadian regulation.
A research community from Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEB
,
Chinese Academy of Sciences
The Chinese Academy of Sciences (CAS); ), known by Academia Sinica in English until the 1980s, is the national academy of the People's Republic of China for natural sciences. It has historical origins in the Academia Sinica during the Republ ...
, sequenced and compared six ''Nannochloropsis''
genomes
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gen ...
that include two ''N. oceanica'' strains (IMET1 and CCMP531) and one strain from each of four other recognized
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
: ''N. salina'' (CCMP537), ''N. gaditana'' (CCMP526, which was previously reported
), ''N. oculata'' (CCMP525) and ''N. granulata'' (CCMP529). They found that the six genomes share key oleaginous traits, such as the
gene dose expansion of selected
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
biosynthesis
genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
compared to
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
''Chlamydomonas''. The most prominent example of
gene dose expansion is
Diacylglycerol acyltransferase
Diglyceride acyltransferase (or O-acyltransferase), DGAT, catalyzes the formation of triglycerides from diacylglycerol and fatty acyl-CoA]. The reaction catalyzed by DGAT is considered the terminal and only committed step in triglyceride synthe ...
(DGAT), which catalyzes the last step of
triacylglycerol
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
(TAG) synthesis. There are 13 DGAT genes in ''Nannochloropsis'', representing the highest
gene dose in known genomes.
Through a comprehensive
phylogenetic analysis
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
, researchers proposed that among the 11 DGAT-2s, one gene might originate from the
red algae
Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...
related secondary
endosymbiont
An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship.
(The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within" ...
, four from
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
related
endosymbiont
An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship.
(The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within" ...
, and the other six from the eukaryotic host genome. In addition, a large proportion (15.3%) of
TAG biosynthesis related
genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
were acquired by ''Nannochloropsis'' via
horizontal gene transfer
Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between Unicellular organism, unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offsprin ...
(HGT) from
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
. Therefore, multiple genome pooling and horizontal genetic exchange, together with selective
inheritance
Inheritance is the practice of receiving private property, Title (property), titles, debts, entitlements, Privilege (law), privileges, rights, and Law of obligations, obligations upon the death of an individual. The rules of inheritance differ ...
of
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
synthesis genes and species-specific gene loss, have led to the enormous genetic apparatus for oleaginousness and the wide genomic divergence among present-day ''Nannochloropsis'' spp.
Accumulation of oil in nitrogen deprivation
When cultured in normal growth conditions i
f/2 medium a standard algal culture
growth medium
A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Differen ...
, supplemented with nitrogen, ''Nannochloropsis'' cells have an oil content of about 30% of their dry weight. This oil can be used to produce
biodiesel
Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with ...
. In order to produce
biodiesel
Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with ...
, the oil content of ''Nannochloropsis'' cultures must be increased. Fatty acid biosynthesis in N. oceanica was shown to be integrated with the regulation of the cholesterol biosynthetic pathway, suggesting new genetic
engineering or chemical biology approaches for enhanced oil production in microalgae. On the other hand, various culturing conditions were observed to increase the average oil content per cell, supporting however only slow growth rates of the cultures (see the related section
Nannochloropsis and biofuels
''Nannochloropsis'' is a genus of alga within the heterokont line of eukaryotes, that is being investigated for biofuel production. One marine ''Nannochloropsis'' species has been shown to be suitable for algal biofuel production due to its ease ...
), and decreasing the overall productivity. Among these conditions, nitrogen deprivation has been one of the most vastly studied. Studies have examined the behaviour of the cultures in nitrogen stress in various culturing set-ups, as well as the physiological and molecular response of the cells to nitrogen deprivation.
Various
strains of ''Nannochloropsis'' were shown to accumulate up to 60–70% of their overall biomass as
lipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
in nitrogen limitation.
In this condition not only the amount of
lipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
changes, but also the composition. It was observed that
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
largely increase in nitrogen depletion while other
lipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
, mainly polar
glycerolipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
, free
fatty acids
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
and
diacylglycerols, slightly decrease. The increase in
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
in nitrogen depletion is much larger than the decrease in the other
glycerolipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
, supporting the hypothesis that the cells actively synthesise new
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
rather than just transforming the existing
lipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
into
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
.
While
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
accumulate and lipid droplets enlarge, other important morphological changes take place. The
chloroplasts
A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
became smaller and the amount of lipids that are characteristic of the
photosynthetic membranes decrease significantly.
Photosynthetic yield decreases in the nitrogen depleted cells, but it is still sufficient to drive cell survival and growth. If
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
is inhibited indeed, ''Nannochloropsis'' cells stop growing, indicating that they rely on
photosynthetic solar energy conversion and not on stored
carbohydrates
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or may ...
or
lipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
as energy source.
''Nannochloropsis'' cultivated in normal growth condition and deprived of a nitrogen source continues growing for 4–5 days. The analysis of
gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. The ...
reveals that mechanisms for
nitrogen assimilation Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that can fix nitrogen gas (N2) depend on the abil ...
and redistribution are activated in the cells in nitrogen scarcity and allow survival through a partial reorganisation of the
cellular metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...
. The genes responsible for the incorporation of free
ammonium
The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...
into
glutamate
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can syn ...
(L-glutamine + 2-oxoglutarate + NADPH + H
+ ←→ 2 L-glutamate + NADP
+) are up-regulated . Their up-regulation increases the capability of the cells to assimilate minimal amount of
ammonium
The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...
eventually present in the medium and, more importantly, allows them to assimilate the intracellular ammonium that can be released by degradative processes.
Transcriptomic
Transcriptomics technologies are the techniques used to study an organism's transcriptome, the sum of all of its RNA transcripts. The information content of an organism is recorded in the DNA of its genome and expressed through transcription. He ...
data of nitrogen-deprived ''Nannochloropsis'' cultures show that various
enzymes
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
responsible for degradative processes that release ammonium are indeed up regulated. Moreover, the expression of genes coding for proteins involved in controlled degradation of proteins increase, together with others involved in the formation of cytosolic sequestering vesicles used for degradation and recycling of cellular components.
The machinery of
gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. The ...
of
chloroplast
A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...
and
mitochondrion
A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
is down regulated in ''Nannochloropsis'' in response to nitrogen depletion.
Corteggiani Carpinelli and coworkers (2013)
report a complete analysis of the
gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. The ...
of ''Nannochloropsis'' cultures grown in normal conditions and nitrogen deprivation for 3 days and 6 days. Data on similar conditions were also collected by Radakovits et al. (2012)
and Vieler et al. (2012).
The all of this data show that genes involved in
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...
and
triacylglycerol
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
biosynthesis are always abundant in the cells and their
expression
Expression may refer to:
Linguistics
* Expression (linguistics), a word, phrase, or sentence
* Fixed expression, a form of words with a specific meaning
* Idiom, a type of fixed expression
* Metaphorical expression, a particular word, phrase, o ...
is not correlated with the amount of oil accumulated. Also the
expression
Expression may refer to:
Linguistics
* Expression (linguistics), a word, phrase, or sentence
* Fixed expression, a form of words with a specific meaning
* Idiom, a type of fixed expression
* Metaphorical expression, a particular word, phrase, o ...
of the
genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
involved in
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
degradation is not significantly
down-regulated as
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
accumulate. The general conclusion suggested by the experimental data is that ''Nannochloropsis'' constitutively produces
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
and that the metabolic reorganisation that follows nitrogen deprivation increases the flux of substrates through this pathway, which is in turn capable to sustain the increased metabolic flux. Corteggiani Carpinelli and coworkers (2013)
advance the hypothesis that, in their experimental conditions,
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
is the main energy source and the down-regulation of the
metabolic activity of the mitochondrion is determinant in increasing the amount of substrates that enter the
fatty acid biosynthetic pathway. If more
precursor
Precursor or Precursors may refer to:
*Precursor (religion), a forerunner, predecessor
** The Precursor, John the Baptist
Science and technology
* Precursor (bird), a hypothesized genus of fossil birds that was composed of fossilized parts of unr ...
s are available, more
fatty acids
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
are synthesised and as a consequence more
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
are produced and accumulated into the cells as oil droplets.
Dong et al. (2013)
report a quantification of the abundance of various
proteins
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
in cultures of ''Nannochloropsis'' grown with a supplement of and deprived of nitrogen. Despite the different experimental conditions, also the
proteomic
Proteomics is the large-scale study of proteins. Proteins are vital parts of living organisms, with many functions such as the formation of structural fibers of muscle tissue, enzymatic digestion of food, or synthesis and replication of DNA. In ...
study seems to support the hypothesis that the accumulation of
triacylglycerols
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
is due to an increase of the metabolic flux through the
fatty acid biosynthetic pathway. The authors advance the hypothesis that, in their experimental conditions, the degradation of
storage sugars and the up-regulation of
glycolysis
Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
are responsible for the increase of substrates through the
pathway.
More recently Li and coworkers (2014)
collected extensive experimental data from cultures of ''Nannochloropsis oculata'' IMET1 grown in nitrogen sufficient and nitrogen depleted media. According to their analysis it is the
catabolism
Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, ...
of
carbohydrates
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or may ...
and
proteins
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
together with the
up-regulation
In the biological context of organisms' production of gene products, downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus. The complementary pro ...
of genes assigned to various
pathways (the cytosolic
glycolysis
Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
pathway, which produces
pyruvate
Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell.
Pyruvic aci ...
; the PDHC bypass, which yields additional
acetyl-CoA
Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for ...
; and the coupling of
TCA reactions with mitochondrial
β-oxidation
In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, ...
) that have to be claimed for increasing the supply of carbon precursors to the
fatty acid biosynthetic pathway. Nevertheless, the authors suggest that it isn't the increased synthesis of
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...
s that leads to accumulation of oil inside the cells, but it is rather the
up-regulation
In the biological context of organisms' production of gene products, downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus. The complementary pro ...
of genes involved in the
assembly of triacylglycerols that determines the final oil concentration. In other words, under nitrogen depletion, it is the
up-regulation
In the biological context of organisms' production of gene products, downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus. The complementary pro ...
of the
transcript level of the key genes in
triacylglycerol assembly, rather than those in
fatty acids biosynthesis, that leads to accelerated
triacylglycerol
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...
production.
In 2017, a study jointly funded by ExxonMobil and Synthetic Genomics achieved a breakthrough in lipid percentages in Nannochloropsis gaditana through applications of the CRISPR-Cas9 reverse-genetics pipeline and nitrogen starving—improving partitioning of total carbon to lipids from 20% (wild type) to 40-45% (mutant type).
See also
*
Microalgae
Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular species which exist indiv ...
*
Planktonic algae
Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), m ...
*
''Nannochloropsis'' and biofuels
*
Biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
*
Sustainable aviation fuel
An aviation biofuel or bio-jet fuel Note: About">Investable Universe>About' or bio-aviation fuel (BAF) is a biofuel used to power aircraft and is said to be a sustainable aviation fuel (SAF). The International Air Transport Association (IATA) co ...
*
Energy content of biofuel The energy content of biofuel is the chemical energy contained in a given biofuel, measured per unit mass of that fuel, as specific energy, or per unit of volume of the fuel, as energy density.
A biofuel is a fuel produced from recently living organ ...
References
External links
*
''Nannochloropsis gaditana'' genome portal''Nannochloropsis'' latest news and scientific reports
''Nannochloropsis gaditana'' CCMP526 web page
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Heterokont genera
Ochrophyta