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In
bacteriology Bacteriology is the branch and specialty of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactio ...
, gram-positive bacteria are
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
that give a positive result in the
Gram stain Gram stain or Gram staining, also called Gram's method, is a method of staining specimen, sandwiched between a glass microscope slide. Staining is a technique used to enhance contrast in samples, generally at the Microscope, microscopic leve ...

Gram stain
test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
. Gram-positive bacteria take up the
crystal violet Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triphenylmethane, triarylmethane dye used as a histological stain and in Gram staining, Gram's method of classifying bacteria. Crystal v ...
stain used in the test, and then appear to be purple-coloured when seen through an
optical microscope The optical microscope, also referred to as a light microscope, is a type of microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory instrument used to examine ob ...
. This is because the thick
peptidoglycan Peptidoglycan or murein is a polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its subsidia ...

peptidoglycan
layer in the bacterial cell wall retains the
stain A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Accidental staining may make materials ...
after it is washed away from the rest of the sample, in the decolorization stage of the test. Conversely,
gram-negative bacteria Gram-negative bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), do ...
cannot retain the violet stain after the decolorization step;
alcohol In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a Saturated and unsaturated compounds, saturated carbon atom. The term alcohol originally referred to the primary alcohol ethan ...

alcohol
used in this stage degrades the outer membrane of gram-negative cells, making the cell wall more porous and incapable of retaining the crystal violet stain. Their
peptidoglycan layer Peptidoglycan or murein is a polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pent ...
is much thinner and sandwiched between an
inner cell membrane cell membrane vs. Prokaryotes A prokaryote is a typically unicellular organism that lacks a nuclear membrane-enclosed cell nucleus, nucleus. The word ''prokaryote'' comes from the Greek language, Greek (, 'before') and (, 'nut' or 'kernel').C ...
and a
bacterial outer membrane 350px, Structure of gram-negative cell envelope The bacterial outer membrane is found in gram-negative bacteria Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bact ...
, causing them to take up the
counterstain 200px, Gram-positive anthrax bacteria with counterstained white blood cells A counterstain is a staining (biology), stain with colour contrasting to the principal stain, making the stained structure easily visible using a microscope. Examples inc ...
(
safranin Safranin (also Safranin O or basic red 2) is a biological stain used in histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology Biology is the natural science that studies life and living organisms ...

safranin
or
fuchsine Fuchsine (sometimes spelled fuchsin) or rosaniline hydrochloride is a magenta dye 300px, Yarn drying after being dyed in the early American tradition, at Conner Prairie living history museum. A dye is a wiktionary:colored, colored substance th ...

fuchsine
) and appear red or pink. Despite their thicker peptidoglycan layer, gram-positive bacteria are more receptive to certain
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...

cell wall
targeting
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...
than gram-negative bacteria, due to the absence of the outer membrane.


Characteristics

In general, the following characteristics are present in gram-positive bacteria: # Cytoplasmic lipid membrane # Thick
peptidoglycan Peptidoglycan or murein is a polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its subsidia ...

peptidoglycan
layer #
Teichoic acids Teichoic acids (''cf.'' Greek τεῖχος, ''teīkhos'', "wall", to be specific a fortification wall, as opposed to τοῖχος, ''toīkhos'', a regular wall) are bacteria Bacteria (; common noun bacteria, singular bacterium) are a ty ...
and lipoids are present, forming
lipoteichoic acid Lipoteichoic acid (LTA) is a major constituent of the cell wall of gram-positive 300px, Violet-stained gram-positive cocci and pink-stained gram-negative bacillus (shape), bacilli In bacteriology, gram-positive bacteria are bacteria that give ...

lipoteichoic acid
s, which serve as
chelating Chelation is a type of bonding of ions An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All ...
agents, and also for certain types of adherence. # Peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme
DD-transpeptidase DD-transpeptidase (, ''DD-peptidase'', ''DD-transpeptidase'', ''DD-carboxypeptidase'', ''D-alanyl-D-alanine carboxypeptidase'', ''D-alanyl-D-alanine-cleaving-peptidase'', ''D-alanine carboxypeptidase'', ''D-alanyl carboxypeptidase'', and ''serine-ty ...
. # A much smaller volume of
periplasm 400px, cell_wall.html"_;"title="Gram-negative_cell_wall">Gram-negative_cell_wall_ The_periplasm_is_a_concentrated_gel-like_matrix_(biology).html" ;"title="cell_wall_.html" ;"title="cell_wall.html" ;"title="Gram-negative cell wall">Gram-negative ce ...
than that in gram-negative bacteria. Only some species have a
capsule Capsule may refer to: Anatomy * Articular capsule (joint capsule), an envelope surrounding a synovial joint * Bowman's capsule (glomerular capsule), a sac surrounding a glomerulus in a mammalian kidney * Glisson's capsule, a fibrous layer covering ...
, usually consisting of
polysaccharides , a beta-glucan polysaccharide Image:amylose 3Dprojection.svg, 350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the o ...
. Also, only some species are
flagellate 's '' Artforms of Nature'', 1904 (''Giardia lamblia'') ('' Chlamydomonas'') A flagellate is a cell or organism with one or more whip-like Appendage, appendages called flagellum, flagella. The word ''flagellate'' also describes a particular const ...
s, and when they do have
flagella A flagellum (; ) is a hairlike appendage that protrudes from a wide range of microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and ...
, have only two
basal body ), 4-Basal body, 5-Cross section of flagellum, 6-Triplets of microtubules of basal body. Image:Chlamydomonas TEM 09.jpg, Longitudinal section through the flagella area in ''Chlamydomonas reinhardtii''. In the cell apex is the basal body that is th ...
rings to support them, whereas gram-negative have four. Both gram-positive and gram-negative bacteria commonly have a surface layer called an
S-layer An S-layer (surface layer) is a part of the cell envelope found in almost all archaea, as well as in many types of bacteria. The S-layers of both archaea and bacteria consists of a monomolecular layer composed of only one (or, in a few cases, two) i ...
. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Gram-negative bacteria's S-layer is attached directly to the outer membrane. Specific to gram-positive bacteria is the presence of
teichoic acid Teichoic acids (''cf.'' Greek τεῖχος, ''teīkhos'', "wall", to be specific a fortification wall, as opposed to τοῖχος, ''toīkhos'', a regular wall) are bacterial copolymers of glycerol phosphate or ribitol, ribitol phosphate and c ...
s in the cell wall. Some of these are lipoteichoic acids, which have a lipid component in the cell membrane that can assist in anchoring the peptidoglycan.


Classification

Along with cell shape, Gram staining is a rapid method used to differentiate bacterial species. Such staining, together with growth requirement and antibiotic susceptibility testing, and other macroscopic and physiologic tests, forms the full basis for classification and subdivision of the bacteria (e.g., see figure and pre-1990 versions of ''
Bergey's Manual ''Bergey's Manual of Systematic Bacteriology'' is the main resource for determining the identity of prokaryotic organisms, emphasizing bacterial species, using every characterizing aspect. The manual was published subsequent to the ''Bergey's Manua ...
'').
Historically History (from Ancient Greek, Greek , ''historia'', meaning "inquiry; knowledge acquired by investigation") is the study of the past. Events occurring before the History of writing#Inventions of writing, invention of writing systems are considered ...

Historically
, the kingdom
Monera Monera (/məˈnɪərə/) (Greek - μονήρης (monḗrēs), "single", "solitary") is a biological kingdom that is made up of prokaryote A prokaryote () is a Unicellular organism, single-celled organism that lacks a cell nucleus, nucleus, a ...
was divided into four
divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of the four basic operations of arithmetic, the ways that numbers are combined to make new numbers. The other operations are addition, subtraction, and multi ...
based primarily on Gram staining:
Firmicutes The Firmicutes (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman ...
(positive in staining),
Gracilicutes Gracilicutes (Latin: ''gracilis'', slender, and ''cutis'', skin, referring to the cell wall) is a clade in bacterial phylogeny. Traditionally gram staining results were most commonly used as a classification tool, consequently until the advent of ...
(negative in staining),
Mollicutes Mollicutes is a class of bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micromet ...
(neutral in staining) and Mendocutes (variable in staining). Based on
16S ribosomal RNA 16 S ribosomal RNA (or 16 S rRNA Ribosomal ribonucleic acid (rRNA) is a type of which is the primary component of s, essential to all cells. rRNA is a which carries out in ribosomes. Ribosomal RNA is transcribed from (rDNA) and then ...
phylogenetic studies of the late microbiologist
Carl Woese Carl Richard Woese (; July 15, 1928 – December 30, 2012) was an American microbiologist A microbiologist (from Greek ) is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an B ...

Carl Woese
and collaborators and colleagues at the
University of Illinois The University of Illinois Urbana-Champaign (U of I, Illinois, or colloquially the University of Illinois or UIUC) is a public university, public land-grant university, land-grant research university in Illinois in the twin cities of Champaign ...
, the
monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
of the gram-positive bacteria was challenged, with major implications for the therapeutic and general study of these organisms. Based on molecular studies of the 16S sequences, Woese recognised twelve
bacterial phyla Bacterial phyla constitute the major lineages of the domain ''Bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic m ...
. Two of these were gram-positive and were divided on the proportion of the
guanine Guanine () (symbol A symbol is a mark, sign, or word In linguistics, a word of a spoken language can be defined as the smallest sequence of phonemes that can be uttered in isolation with semantic, objective or pragmatics, practical me ...

guanine
and
cytosine Cytosine () (symbol A symbol is a mark, sign, or that indicates, signifies, or is understood as representing an , , or . Symbols allow people to go beyond what is n or seen by creating linkages between otherwise very different s and s. Al ...

cytosine
content in their
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
. The high G + C phylum was made up of the
Actinobacteria The Actinobacteria are a phylum of mostly Gram-positive bacteria File:Gram stain 01.jpg, 300px, Violet-stained gram-positive cocci and pink-stained gram-negative bacillus (shape), bacilli In bacteriology, gram-positive bacteria are bacteria tha ...
and the low G + C phylum contained the
Firmicutes The Firmicutes (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman ...
. The Actinobacteria include the ''
Corynebacterium ''Corynebacterium'' () is a of that are and most are . They are (rod-shaped), and in some phases of life they are, more specifically, -shaped, which inspired the genus name (' means "club-shaped"). They are widely distributed in nature in th ...

Corynebacterium
'', ''
Mycobacterium ''Mycobacterium'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer ...
'', ''
Nocardia ''Nocardia'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...

Nocardia
'' and ''
Streptomyces ''Streptomyces'' is the largest genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ma ...
'' genera. The (low G + C) Firmicutes, have a 45–60% GC content, but this is lower than that of the Actinobacteria.


Importance of the outer cell membrane in bacterial classification

Although bacteria are traditionally divided into two main groups, gram-positive and gram-negative, based on their Gram stain retention property, this classification system is ambiguous as it refers to three distinct aspects (staining result, envelope organization, taxonomic group), which do not necessarily coalesce for some bacterial species. The gram-positive and gram-negative staining response is also not a reliable characteristic as these two kinds of bacteria do not form phylogenetic coherent groups. However, although Gram staining response is an empirical criterion, its basis lies in the marked differences in the ultrastructure and chemical composition of the bacterial cell wall, marked by the absence or presence of an outer lipid membrane. All gram-positive bacteria are bounded by a single-unit lipid membrane, and, in general, they contain a thick layer (20–80 nm) of peptidoglycan responsible for retaining the Gram stain. A number of other bacteria—that are bounded by a single membrane, but stain gram-negative due to either lack of the peptidoglycan layer, as in the
mycoplasma ''Mycoplasma'' (plural mycoplasmas or mycoplasmata) is a genus of bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokary ...
s, or their inability to retain the Gram stain because of their cell wall composition—also show close relationship to the Gram-positive bacteria. For the bacterial cells bounded by a single cell membrane, the term ''monoderm bacteria'' has been proposed. In contrast to gram-positive bacteria, all typical gram-negative bacteria are bounded by a cytoplasmic membrane and an outer cell membrane; they contain only a thin layer of peptidoglycan (2–3 nm) between these membranes. The presence of inner and outer cell membranes defines a new compartment in these cells: the
periplasmic space 400px, cell_wall.html"_;"title="Gram-negative_cell_wall">Gram-negative_cell_wall_ The_periplasm_is_a_concentrated_gel-like_matrix_(biology).html" ;"title="cell_wall_.html" ;"title="cell_wall.html" ;"title="Gram-negative cell wall">Gram-negative ce ...
or the periplasmic compartment. These bacteria have been designated as diderm bacteria. The distinction between the monoderm and diderm bacteria is supported by conserved signature indels in a number of important proteins (viz. DnaK, GroEL). Of these two structurally distinct groups of bacteria, monoderms are indicated to be ancestral. Based upon a number of observations including that the gram-positive bacteria are the major producers of antibiotics and that, in general, gram-negative bacteria are resistant to them, it has been proposed that the outer cell membrane in gram-negative bacteria (diderms) has evolved as a protective mechanism against
antibiotic An antibiotic is a type of antimicrobial An antimicrobial is an agent that kills microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system t ...
selection pressure. Some bacteria, such as ''
Deinococcus ''Deinococcus'' (from the el, δεινός, ''deinos'', "dreadful, strange" and κόκκος, ''kókkos'', "granule") is one genus of three in the order Deinococcales of the bacterial phylum ''Deinococcus''-''Thermus'' highly resistant to envir ...
'', which stain gram-positive due to the presence of a thick peptidoglycan layer and also possess an outer cell membrane are suggested as intermediates in the transition between monoderm (gram-positive) and diderm (gram-negative) bacteria. The diderm bacteria can also be further differentiated between simple diderms lacking lipopolysaccharide, the archetypical diderm bacteria where the outer cell membrane contains lipopolysaccharide, and the diderm bacteria where outer cell membrane is made up of
mycolic acidMycolic acids are long fatty acid fatty acids have perfectly straight chain structure. Unsaturated ones are typically bent, unless they have a trans configuration. In chemistry Chemistry is the scientific discipline involved with Chemical ...
.


Exceptions

In general, gram-positive bacteria are monoderms and have a single
lipid bilayer The lipid bilayer (or phospholipid bilayer) is a thin polar membrane A polarized membrane is a lipid bilayer, lipid membrane that has a positive electrical charge on one side and a negative charge on another side, which produces the resting pot ...
whereas gram-negative bacteria are diderms and have two bilayers. Some taxa lack peptidoglycan (such as the class
Mollicutes Mollicutes is a class of bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micromet ...
, some members of the
Rickettsiales The Rickettsiales, informally called rickettsias, are an order of small Alphaproteobacteria. Some are notable pathogens, including ''Rickettsia'', which causes a variety of diseases in humans, and ''Ehrlichia'', which causes diseases in livestock. ...
, and the insect-endosymbionts of the
Enterobacteriales Enterobacterales with its type genus ''Enterobacter'' is an order of Gram-negative bacteria Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacterial differentiati ...
) and are gram-variable. This, however, does not always hold true. The '' Deinococcus-Thermus'' bacteria have gram-positive stains, although they are structurally similar to gram-negative bacteria with two layers. The Chloroflexi have a single layer, yet (with some exceptions) stain negative. Two related phyla to the Chloroflexi, the TM7 clade and the Ktedonobacteria, are also monoderms. Some Firmicute species are not gram-positive. These belong to the class
Mollicutes Mollicutes is a class of bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micromet ...
(alternatively considered a class of the phylum
Tenericutes Tenericutes (tener cutis: soft skin) is a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of ...
), which lack peptidoglycan ( gram-indeterminate), and the class Negativicutes, which includes Selenomonas and stain gram-negative. Additionally, a number of bacterial taxa (viz.
Negativicutes The Negativicutes are a class of bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few ...
,
Fusobacteria Fusobacteria are obligately anaerobic non-sporeforming Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacterial differentiation. They are characteriz ...
, , and
Elusimicrobia The phylum Elusimicrobia, previously known as "Termite Group 1", has been shown to be widespread in different ecosystems like marine environment, sewage sludge, contaminated sites and soils, and toxic wastes. The high abundance of 'Elusimicrobia' ...
) that are either part of the phylum Firmicutes or branch in its proximity are found to possess a diderm cell structure. However, a conserved signature indel (CSI) in the
HSP60 HSP60, also known as chaperonins (Cpn), is a family of heat shock proteinsHeat shock proteins (HSP) are a family of proteins Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have i ...
(
GroEL GroEL is a protein which belongs to the family of , and is found in many bacteria. It is required for the proper of many proteins. To function properly, GroEL requires the lid-like cochaperonin protein complex . In the proteins Hsp60 and Hsp1 ...

GroEL
) protein distinguishes all traditional phyla of gram-negative bacteria (e.g.,
Proteobacteria Proteobacteria is a major phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plu ...
,
Aquificae The Aquificae phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a nou ...
,
Chlamydiae The Chlamydiae are a bacterial Phylum (biology), phylum and Class (biology), class whose members are remarkably diverse, including pathogens of humans and animals, symbiosis, symbionts of ubiquitous protozoa, and marine sediment forms not yet wel ...
,
Bacteroidetes The phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typicall ...
,
Chlorobi The green sulfur bacteria (Chlorobiaceae) are a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of ...

Chlorobi
,
Cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical ...

Cyanobacteria
,
Fibrobacteres Fibrobacteres is a small bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micromet ...

Fibrobacteres
,
Verrucomicrobia Verrucomicrobia is a phylum of Gram-negative bacteria Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacterial differentiation. They are characterized by their cell ...
,
Planctomycetes The Planctomycetes are a phylum of widely distributed bacteria, occurring in both water, aquatic and terrestrial habitats. They play a considerable role in global carbon and nitrogen cycles, with many species of this phylum capable of anaerobic amm ...
, Spirochetes,
Acidobacteria Acidobacteria is a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of ...
, etc.) from these other atypical diderm bacteria, as well as other phyla of monoderm bacteria (e.g., Actinobacteria, Firmicutes,
Thermotogae The Thermotogae are a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural ...
, Chloroflexi, etc.). The presence of this CSI in all sequenced species of conventional LPS (
lipopolysaccharide Lipopolysaccharides (LPS) are large molecule A molecule is an electrically Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change ...

lipopolysaccharide
)-containing gram-negative bacterial phyla provides evidence that these phyla of bacteria form a monophyletic clade and that no loss of the outer membrane from any species from this group has occurred.


Pathogenesis

In the classical sense, six gram-positive genera are typically pathogenic in humans. Two of these, ''
Streptococcus ''Streptococcus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), ...

Streptococcus
'' and ''
Staphylococcus ''Staphylococcus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy) ...
'', are
cocci A coccus (plural cocci) is any bacterium Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological ...
(sphere-shaped). The remaining organisms are
bacilli Bacilli is a taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally ...
(rod-shaped) and can be subdivided based on their ability to form
spore In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...
s. The non-spore formers are ''
Corynebacterium ''Corynebacterium'' () is a of that are and most are . They are (rod-shaped), and in some phases of life they are, more specifically, -shaped, which inspired the genus name (' means "club-shaped"). They are widely distributed in nature in th ...

Corynebacterium
'' and ''
Listeria ''Listeria'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to ...

Listeria
'' (a coccobacillus), whereas ''
Bacillus ''Bacillus'' (Latin "stick") is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ma ...

Bacillus
'' and ''
Clostridium ''Clostridium'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, virus ...
'' produce spores. The spore-forming bacteria can again be divided based on their
respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellular ...

respiration
: ''Bacillus'' is a
facultative anaerobe 300px, Aerobic and anaerobic bacteria can be identified by growing them in test tubes of thioglycolate broth: 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen ...
, while ''Clostridium'' is an
obligate anaerobe Obligate anaerobes are microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical stru ...
. Also, ''Rathybacter'', ''Leifsonia'', and ''Clavibacter'' are three gram-positive genera that cause plant disease. Gram-positive bacteria are capable of causing serious and sometimes fatal
infections An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the infectious agents and the toxins they produce. An in ...
in newborn infants. Access provided by the University of Pittsburgh. Novel species of clinically relevant gram-positive bacteria also include '' Catabacter hongkongensis'', which is an emerging pathogen belonging to
Firmicutes The Firmicutes (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman ...
.


Bacterial transformation

Transformation Transformation may refer to: Science and mathematics In biology and medicine * Metamorphosis, the biological process of changing physical form after birth or hatching * Malignant transformation, the process of cells becoming cancerous * Transf ...
is one of three processes for
horizontal gene transfer Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between unicellular A unicellular organism, also known as a single-celled organism, is an organism In biology, an organism (from Ancient G ...
, in which exogenous genetic material passes from a donor bacterium to a recipient bacterium, the other two processes being
conjugation Conjugation or conjugate may refer to: Linguistics * Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics * Complex conjugation, the change ...
(transfer of
genetic material Nucleic acids are biopolymer Biopolymers are natural polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese busin ...
between two bacterial cells in direct contact) and (injection of donor bacterial DNA by a
bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, ...

bacteriophage
virus into a recipient host bacterium). In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium. As of 2014 about 80 species of bacteria were known to be capable of transformation, about evenly divided between gram-positive and
gram-negative bacteria Gram-negative bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), do ...
; the number might be an overestimate since several of the reports are supported by single papers. Transformation among gram-positive bacteria has been studied in medically important species such as ''
Streptococcus pneumoniae ''Streptococcus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

Streptococcus pneumoniae
'', ''
Streptococcus mutans ''Streptococcus mutans'' is a facultatively anaerobic, gram-positive 300px, Violet-stained gram-positive cocci and pink-stained gram-negative bacillus (shape), bacilli In bacteriology, gram-positive bacteria are bacteria that give a positive ...
'', ''
Staphylococcus aureus ''Staphylococcus aureus'' is a Gram-positive bacteria, Gram-positive coccus, round-shaped bacterium, a member of the Firmicutes, and is a usual member of the microbiota of the body, frequently found in the Respiratory tract, upper respiratory ...
'' and '' Streptococcus sanguinis'' and in gram-positive soil bacterium ''
Bacillus subtilis ''Bacillus subtilis'', known also as the hay bacillus or grass bacillus, is a Gram-positive 300px, Violet-stained gram-positive cocci and pink-stained gram-negative bacillus (shape), bacilli In bacteriology, gram-positive bacteria are bacteria ...

Bacillus subtilis
, Bacillus cereus''.


Orthographic note

The adjectives ''Gram-positive'' and ''Gram-negative'' derive from the surname of
Hans Christian Gram Hans Christian Joachim Gram (13 September 1853 – 14 November 1938) was a Danish bacteriologist A bacteriologist is a microbiologist or a professional trained in bacteriology, a subdivision of microbiology. The duties of a bacteriologist inclu ...
; as eponymous adjectives, their initial letter can be either capital ''G'' or lower-case ''g'', depending on which
style guide A style guide or manual of style is a set of standards for the writing, formatting, and design of documents A document is a writing, written, drawing, drawn, presented, or memorialized representation of thought, often the manifestation of ...
(e.g., that of the
CDC CDC may refer to: Organizations Government * Centers for Disease Control and Prevention The United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous Unite ...
), if any, governs the document being written. This is further explained at '' Gram staining § Orthographic note''.


References


External links

*
3D structures of proteins associated with plasma membrane of gram-positive bacteria

3D structures of proteins associated with outer membrane of gram-positive bacteria
{{Authority control Staining Bacteriology