''Nannochloropsis'' is a
genus of
algae comprising six known
species. The
genus in the current
taxonomic classification 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 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 ''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'' and ''
chlorophyll c''. In addition they are able to build up a high concentrations of a range of pigments such as
astaxanthin,
zeaxanthin 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.
Moreover, it shows promising features that can allow
genetic manipulation 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 o ...
). ''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,
Spain) 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
''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and ...
''
Fawley, Jameson & Fawley 2015
* ''
Nannochloropsis gaditana
''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and ...
''
Lubián 1982
* ''
Nannochloropsis granulata
''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh a ...
''
Karlson & Potter 1996
* ''
Nannochloropsis limnetica
''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh a ...
''
Krienitz et al. 2000
* ''
Nannochloropsis oceanica
''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and ...
''
Suda & Miyashita 2002
* ''
Nannochloropsis oculata
''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and ...
''
(Droop 1955) Hibberd 1981
* ''
Nannochloropsis salina
''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and ...
''
Hibberd 1981
Sequenced genomes
The scientific community has obtained the
genomic sequence of different
strains of ''Nannochloropsis'' belonging to two
species: ''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, moreover dedicated web pages are also available for the genomes o
''N. gaditana'' CCMP526an
The
genomes of the sequenced ''Nannochloropsis''
strains were between 28.5 and 29 Mega bases long, they had high density of
genes, 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 share extended similarity.
The analysis of the
genomes 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 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 analysis of whole algal cells which were cultivated in
autotrophic growth reports evidence of the presence of
cellulose 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 inside the cell.
Comparison between the
lipid metabolic genes of ''N. gaditana'' and of
red/
green/
brown algae and
diatoms 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 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 of ''Nannochloropsis'' of
regulatory RNA and in particular
miRNA.
Various
orthologs 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, sequenced and compared six ''Nannochloropsis''
genomes that include two ''N. oceanica'' strains (IMET1 and CCMP531) and one strain from each of four other recognized
species: ''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 Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order ...
expansion of selected
lipid 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 Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order ...
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 synth ...
(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 Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order ...
in known genomes.
Through a comprehensive
phylogenetic analysis, 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, 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, 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 (HGT) from
bacteria. Therefore, multiple genome pooling and horizontal genetic exchange, together with selective
inheritance of
lipid 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. In order to produce
biodiesel, 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 o ...
), 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 in nitrogen limitation.
In this condition not only the amount of
lipids 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, mainly polar
glycerolipids, free
fatty acids and
diacylglycerols
A diglyceride, or diacylglycerol (DAG), is a glyceride consisting of two fatty acid chains covalently bonded to a glycerol molecule through ester linkages. Two possible forms exist, 1,2-diacylglycerols and 1,3-diacylglycerols. DAGs can act as sur ...
, 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, 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 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 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 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 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 and redistribution are activated in the cells in nitrogen scarcity and allow survival through a partial reorganisation of the
cellular metabolism. 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 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 is not correlated with the amount of oil accumulated. Also the
expression 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 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
precursors are available, more
fatty acids 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 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
Pathway or pathways may refer to:
Entertainment
* ''The Pathway'' (novel), a 1914 work by Gertrude Page
*''The Pathway'', a 2001 album by Officium Triste
* ''Pathway'' (album), by the Flaming Stars
* ''Pathways'' (album) (2010), by the Dave Hol ...
.
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
pathway
Pathway or pathways may refer to:
Entertainment
* ''The Pathway'' (novel), a 1914 work by Gertrude Page
*''The Pathway'', a 2001 album by Officium Triste
* ''Pathway'' (album), by the Flaming Stars
* ''Pathways'' (album) (2010), by the Dave Hol ...
s (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 acids 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
*
Energy content of biofuel
References
External links
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''Nannochloropsis gaditana'' genome portal''Nannochloropsis'' latest news and scientific reports
''Nannochloropsis gaditana'' CCMP526 web page
{{Authority control
Heterokont genera
Ochrophyta