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300px, Violet-stained gram-positive cocci_and_pink-stained_gram-negative_bacillus_(shape).html" "title="gram-negative.html" ;"title="cocci and pink-stained gram-negative">cocci and pink-stained gram-negative bacillus (shape)">bacilli Bacilli is a taxonomic class of bacteria that includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens such as ''Bacillus anthracis'' (the cause of anthrax). ''Bacilli'' are almost exclusively gram-positive ...
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the 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. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mecha ...
. 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 triarylmethane dye used as a histological stain and in Gram's method of classifying bacteria. Crystal violet has antibacterial, antifung ...
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 that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of microscop ...
. This is because the thick
peptidoglycan Peptidoglycan or murein is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall. The sugar component consists of alternating residues of β-(1,4) linked ''N' ...
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 app ...
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 that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall san ...
cannot retain the violet stain after the decolorization step;
alcohol upright=0.8, The bond angle between a hydroxyl group (-OH) and a chain of carbon atoms (R) In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a saturated carbon atom. The term alcoh ...

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 consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall. The sugar component consists of alternating residues of β-(1,4) linked ''N' ...
is much thinner and sandwiched between an
inner cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates the interior of all cells from the outside ...
and a
bacterial outer membrane 350px, Structure of gram-negative cell envelope The bacterial outer membrane is found in gram-negative bacteria. Its composition is distinct from that of the inner cytoplasmic cell membrane - among other things, the outer leaflet of the outer membr ...
, causing them to take up the
counterstain 200px, Gram-positive anthrax bacteria with counterstained white blood cells A counterstain is a stain with colour contrasting to the principal stain, making the stained structure easily visible using a microscope. Examples include the malachite gree ...
(
safranin Safranin (also Safranin O or basic red 2) is a biological stain used in histology and cytology. Safranin is used as a counterstain in some staining protocols, colouring cell nuclei red. This is the classic counterstain in both Gram stains and endo ...
or
fuchsine Fuchsine (sometimes spelled fuchsin) or rosaniline hydrochloride is a magenta dye with chemical formula C20H19N3·HCl.
) 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. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mecha ...
targeting
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of su ...
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 consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall. The sugar component consists of alternating residues of β-(1,4) linked ''N' ...
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 bacterial copolymers of glycerol phosphate or ribitol phosphate and carbohydrat ...
and lipoids are present, forming
lipoteichoic acid Lipoteichoic acid (LTA) is a major constituent of the cell wall of gram-positive bacteria. These organisms have an inner (or cytoplasmic) membrane and, external to it, a thick (up to 80 nanometer) peptidoglycan layer. The structure of LTA varies b ...

lipoteichoic acid
s, which serve as
chelating Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central atom. These ligands are called ...
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
periplasm400px, cell_wall.html"_style="text-decoration:_none;"class="mw-redirect"_title="Gram-negative_cell_wall">Gram-negative_cell_wall_ The_periplasm_is_a_concentrated_gel-like_matrix_(biology).html" style="text-decoration: none;"class="mw-redirect" ...
than that in gram-negative bacteria. Only some species have a capsule, 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, th ...
. 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 appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of org ...
s, and when they do have
flagella A flagellum (; plural: flagella) is a lash-like appendage that protrudes from the cell body of certain cells termed as flagellates. A flagellate can have one or several flagella. The primary function of a flagellum is that of locomotion, but it ...
, 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-layerAn S-layer (surface layer) is a part of the cell envelope found in almost all archaea, as well as in many types of bacteria. It consists of a monomolecular layer composed of identical proteins or glycoproteins. This structure is built via self-assemb ...
. 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 phosphate and carbohydrat ...
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'').
Historically History (from Greek , ''historia'', meaning "inquiry; knowledge acquired by investigation") is the study of the past. Events occurring before the invention of writing systems are considered prehistory. "History" is an umbrella term that relates t ...

Historically
, the kingdom
Monera Monera () (Greek - μονήρης (monḗrēs), "single", "solitary") is a kingdom that contains unicellular organisms with a prokaryotic cell organization (having no nuclear membrane), such as bacteria. They are single-celled organisms with no t ...
was divided into four
divisions Division or divider may refer to: Mathematics *Division (mathematics), the inverse of multiplication *Division algorithm, a method for computing the result of mathematical division Military *Division (military), a formation typically consisting o ...
based primarily on Gram staining:
Firmicutes The Firmicutes (Latin: ''firmus'', strong, and ''cutis'', skin, referring to the cell wall) are a phylum of bacteria, most of which have gram-positive cell wall structure. A few, however, such as ''Megasphaera'', ''Pectinatus'', ''Selenomonas'' and ...
(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 distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin ''mollis'' (meaning "soft" or "pliable"), and ''cutis'' (meaning "skin"). Individuals are very small, typically only 0.2 ...
(neutral in staining) and Mendocutes (variable in staining). Based on
16S ribosomal RNA 16S ribosomal RNA (or 16S rRNA) is the RNA component of the 30S small subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S rRN ...
phylogenetic studies of the late microbiologist
Carl Woese Carl Richard Woese (; July 15, 1928 – December 30, 2012) was an American microbiologist and biophysicist. Woese is famous for defining the Archaea (a new domain of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique he pionee ...

Carl Woese
and collaborators and colleagues at the
University of Illinois A university ( la, universitas, 'a whole') is an institution of higher (or tertiary) education and research which awards academic degrees in various academic disciplines. Universities typically offer both undergraduate and postgraduate programs. ...
, the
monophyly 300px, A cladogram of the primates, showing a ''monophyletic'' taxon: ''the simians'' (in yellow); a ''paraphyletic'' taxon: ''the prosimians'' (in cyan, including the red patch); and a ''polyphyletic'' group: ''the night-active primates, i.e., ...
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''. While the exact definition of a bacterial phylum is debated, a popular definition is that a bacterial phylum is a monophyletic lineage of bacteria whose 16S rRNA genes shar ...
. Two of these were gram-positive and were divided on the proportion of the
guanine Guanine (; or G, Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine (uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is called guanosine. ...

guanine
and
cytosine Cytosine (; C) is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at positio ...
content in their
DNA The structure of part of a DNA double helix Deoxyribonucleic acid (; DNA) is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, g ...
. The high G + C phylum was made up of the
Actinobacteria The Actinobacteria are a phylum of mostly Gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to soil systems. In soil they help ...
and the low G + C phylum contained the
Firmicutes The Firmicutes (Latin: ''firmus'', strong, and ''cutis'', skin, referring to the cell wall) are a phylum of bacteria, most of which have gram-positive cell wall structure. A few, however, such as ''Megasphaera'', ''Pectinatus'', ''Selenomonas'' and ...
. The Actinobacteria include the ''
Corynebacterium ''Corynebacterium'' () is a genus of bacteria that are Gram-positive and aerobic. They are bacilli (rod-shaped), and in some phases of life they are, more particularly, club-shaped, which inspired the genus name (''coryneform'' means "club-shaped" ...
'', ''
Mycobacterium ''Mycobacterium'' is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. Over 190 species are recognized in this genus. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (''Mycobact ...
'', ''
Nocardia ''Nocardia'' is a genus of weakly staining Gram-positive, catalase-positive, rod-shaped bacteria. It forms partially acid-fast beaded branching filaments (acting as fungi, but being truly bacteria). It contains a total of 85 species. Some species ...
'' and ''
Streptomyces ''Streptomyces'' is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae. Over 500 species of ''Streptomyces'' bacteria have been described. As with the other Actinobacteria, streptomycetes are gram-positive, a ...
'' 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 that lack a cell wall around their cell membranes. This characteristic makes them naturally resistant to antibiotics that target cell wall synthesis (like the beta-lact ...
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 space400px, cell_wall.html"_style="text-decoration:_none;"class="mw-redirect"_title="Gram-negative_cell_wall">Gram-negative_cell_wall_ The_periplasm_is_a_concentrated_gel-like_matrix_(biology).html" style="text-decoration: none;"class="mw-redirect" ...
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 substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of su ...
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 environ ...
'', 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 acids found in the cell walls of the Mycolata taxon, a group of bacteria that includes ''Mycobacterium tuberculosis'', the causative agent of the disease tuberculosis. They form the major component of the cell wall of my ...
.


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 made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many virus ...
whereas gram-negative bacteria are diderms and have two bilayers. Some taxa lack peptidoglycan (such as the domain
Archaea Archaea ( ; singular archaeon ) constitute a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archae ...
, the class
Mollicutes Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin ''mollis'' (meaning "soft" or "pliable"), and ''cutis'' (meaning "skin"). Individuals are very small, typically only 0.2 ...
, 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. Historical identification and systematics Enterobacterales was proposed in 2005 under the name "Enterobacteriales". However, the name "Enterobacterial ...
) 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 distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin ''mollis'' (meaning "soft" or "pliable"), and ''cutis'' (meaning "skin"). Individuals are very small, typically only 0.2 ...
(alternatively considered a class of the phylum
Tenericutes Tenericutes (tener cutis: soft skin) is a phylum of bacteria that contains the class Mollicutes. The name was validated in 1984 as a new division (phylum).Ludwig, W.; Schleifer, K.-H., and Whitman, W.B. (In press, release in 2009). "Revised road m ...
), which lack peptidoglycan ( gram-indeterminate), and the class Negativicutes, which includes Selenomonas and stain gram-negative. Additionally, a number of bacterial taxa (viz. Negativicutes, Fusobacteria, Synergistetes, and 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 (GroEL) protein distinguishes all traditional phyla of gram-negative bacteria (e.g., Proteobacteria, Aquificae, Chlamydiae, Bacteroidetes, Chlorobi, Cyanobacteria, Fibrobacteres, Verrucomicrobia, Planctomycetes, Spirochetes, Acidobacteria, etc.) from these other atypical diderm bacteria, as well as other phyla of monoderm bacteria (e.g., Actinobacteria, Firmicutes, Thermotogae, Chloroflexi, etc.). The presence of this CSI in all sequenced species of conventional LPS (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'' and ''Staphylococcus'', are Coccus, cocci (sphere-shaped). The remaining organisms are bacilli (rod-shaped) and can be subdivided based on their ability to form endospore, spores. The non-spore formers are ''
Corynebacterium ''Corynebacterium'' () is a genus of bacteria that are Gram-positive and aerobic. They are bacilli (rod-shaped), and in some phases of life they are, more particularly, club-shaped, which inspired the genus name (''coryneform'' means "club-shaped" ...
'' and ''Listeria'' (a coccobacillus), whereas ''Bacillus'' and ''Clostridium'' produce spores. The spore-forming bacteria can again be divided based on their Cellular respiration, respiration: ''Bacillus'' is a Facultative anaerobic organism, facultative anaerobe, while ''Clostridium'' is an obligate anaerobe. 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 neonatal infection, infections 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: ''firmus'', strong, and ''cutis'', skin, referring to the cell wall) are a phylum of bacteria, most of which have gram-positive cell wall structure. A few, however, such as ''Megasphaera'', ''Pectinatus'', ''Selenomonas'' and ...
.


Bacterial transformation

Transformation (genetics), Transformation is one of three processes for horizontal gene transfer, in which exogenous genetic material passes from a donor bacterium to a recipient bacterium, the other two processes being bacterial conjugation, conjugation (transfer of plasmid, genetic material between two bacterial cells in direct contact) and transduction (genetics), transduction (injection of donor bacterial DNA by a 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 that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall san ...
; 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 mutans'', ''Staphylococcus aureus'' and ''Streptococcus sanguinis'' and in gram-positive soil bacterium ''Bacillus subtilis, Bacillus cereus''.


Orthographic note

The adjectives ''Gram-positive'' and ''Gram-negative'' derive from the surname of Hans Christian Gram; as Eponym#Orthographic conventions, eponymous adjectives, their initial letter can be either capital ''G'' or lower-case ''g'', depending on which style guide (e.g., that of the Centers for Disease Control and Prevention, CDC), if any, governs the document being written. This is further explained at ''Gram staining#Orthographic note, 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
{{portal bar, Biology Gram-positive bacteria, Staining Bacteriology