HOME
The Info List - Gram-positive


--- Advertisement ---



Gram-positive bacteria
Gram-positive bacteria
are bacteria that give a positive result in the Gram stain
Gram stain
test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall. Gram-positive bacteria
Gram-positive bacteria
take up the crystal violet stain used in the test, and then appear to be purple-coloured when seen through a microscope. This is because the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test. Gram-negative bacteria
Gram-negative bacteria
cannot retain the violet stain after the decolorization step; 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 is much thinner and sandwiched between an inner cell membrane and a bacterial outer membrane, causing them to take up the counterstain (safranin or fuchsine) and appear red or pink. Despite their thicker peptidoglycan layer, Gram-positive bacteria
Gram-positive bacteria
are more receptive to antibiotics than Gram-negative, due to the absence of the outer membrane.

Contents

1 Characteristics 2 Classification 3 Importance of the outer cell membrane in bacterial classification

3.1 Exceptions

4 Pathogenesis 5 Bacterial transformation 6 Orthographic note 7 References 8 External links

Characteristics[edit]

Gram-positive and -negative cell wall structure

Structure of Gram-positive cell wall

In general, the following characteristics are present in Gram-positive bacteria:[1]

Cytoplasmic lipid membrane Thick peptidoglycan layer Teichoic acids
Teichoic acids
and lipoids are present, forming lipoteichoic acids, which serve as chelating agents, and also for certain types of adherence. Peptidoglycan
Peptidoglycan
chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase. A much smaller volume of periplasm than that in Gram-negative bacteria.

Only some species have a capsule, usually consisting of polysaccharides. Also, only some species are flagellates, and when they do have flagella, have only two basal body 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. In Gram-positive bacteria, the S-layer
S-layer
is attached to the peptidoglycan layer. Gram-negative bacteria's S-layer
S-layer
is attached directly to the outer membrane). Specific to Gram-positive bacteria
Gram-positive bacteria
is the presence of teichoic acids 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[edit] 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).

Species identification hierarchy in clinical settings

Historically, the kingdom Monera
Monera
was divided into four divisions based primarily on Gram staining: Firmicutes
Firmicutes
(positive in staining), Gracilicutes
Gracilicutes
(negative in staining), Mollicutes
Mollicutes
(neutral in staining) and Mendocutes (variable in staining).[2] Based on 16S ribosomal RNA phylogenetic studies of the late microbiologist Carl Woese
Carl Woese
and collaborators and colleagues at the University of Illinois, the monophyly of the Gram-positive bacteria
Gram-positive bacteria
was challenged,[3] 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. Two of these were both Gram-positive and were divided on the proportion of the guanine and cytosine content in their DNA. The high G + C phylum was made up of the Actinobacteria
Actinobacteria
and the low G + C phylum contained the Firmicutes.[3] The Actinobacteria include the Corynebacterium, Mycobacterium, Nocardia
Nocardia
and Streptomyces genera. The (low G + C) Firmicutes, have a 45–60% GC content, but this is lower than that of the Actinobacteria.[1] Importance of the outer cell membrane in bacterial classification[edit]

The structure of peptidoglycan, composed of N-acetylglucosamine
N-acetylglucosamine
and N-acetylmuramic acid

Although bacteria are traditionally divided into two main groups, Gram-positive and Gram-negative, based on their Gram stain
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.[4][5][6][7] 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.[4] 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.[4][8] All Gram-positive bacteria
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 Mycoplasmas, or their inability to retain the Gram stain
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" or "monoderm prokaryotes" has been proposed.[4][8] In contrast to Gram-positive bacteria, all archetypical 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 or the periplasmic compartment. These bacteria have been designated as "diderm bacteria."[4][8] The distinction between the monoderm and diderm bacteria is supported by conserved signature indels in a number of important proteins (viz. DnaK, GroEL).[4][5][8][9] 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
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
Gram-negative bacteria
(diderms) has evolved as a protective mechanism against antibiotic selection pressure.[4][5][8][9] Some bacteria, such as Deinococcus, 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.[4][9] 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 acid.[6][9][10] Exceptions[edit] In general, Gram-positive bacteria
Gram-positive bacteria
are monoderms and have a single lipid bilayer whereas Gram-negative bacteria
Gram-negative bacteria
are diderms and have two bilayers. Some taxa lack peptidoglycan (such as the domain Archaea, the class Mollicutes, some members of the Rickettsiales, and the insect-endosymbionts of the Enterobacteriales) 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
Gram-negative bacteria
with two layers. The Chloroflexi have a single layer, yet (with some exceptions[11]) stain negative.[12] Two related phyla to the Chloroflexi, the TM7
TM7
clade and the Ktedonobacteria, are also monoderms.[13][14] Some Firmicute species are not Gram-positive. These belong to the class Mollicutes
Mollicutes
(alternatively considered a class of the phylum Tenericutes), which lack peptidoglycan (Gram-indeterminate), and the class Negativicutes, which includes Selenomonas
Selenomonas
and stain Gram-negative.[10] Additionally, a number of bacterial taxa (viz. Negativicutes, Fusobacteria, Synergistetes, and Elusimicrobia) that are either part of the phylum Firmicutes
Firmicutes
or branch in its proximity are found to possess a diderm cell structure.[7][9][10] However, a conserved signature indel (CSI) in the HSP60
HSP60
(GroEL) protein distinguishes all traditional phyla of Gram-negative bacteria
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.).[9] 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.[9] Pathogenesis[edit]

Colonies of a Gram-positive pathogen of the oral cavity, Actinomyces sp.

In the classical sense, six Gram-positive genera are typically pathogenic in humans. Two of these, Streptococcus
Streptococcus
and Staphylococcus, are cocci (sphere-shaped). The remaining organisms are bacilli (rod-shaped) and can be subdivided based on their ability to form spores. The non-spore formers are Corynebacterium
Corynebacterium
and Listeria
Listeria
(a coccobacillus), whereas Bacillus
Bacillus
and Clostridium
Clostridium
produce spores.[15] The spore-forming bacteria can again be divided based on their respiration: Bacillus
Bacillus
is a facultative anaerobe, while Clostridium
Clostridium
is an obligate anaerobe.[16] Also, Rathybacter, Leifsonia, and Clavibacter are three Gram-positive genera that cause plant disease. Gram-positive bacteria
Gram-positive bacteria
are capable of causing serious and sometimes fatal infections in newborn infants.[17] Bacterial transformation[edit] 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 conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of donor bacterial DNA
DNA
by a bacteriophage virus into a recipient host bacterium).[18] In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium.[18] 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; the number might be an overestimate since several of the reports are supported by single papers.[18] Transformation among Gram-positive bacteria
Gram-positive bacteria
has been studied in medically important species such as Streptococcus
Streptococcus
pneumoniae, Streptococcus
Streptococcus
mutans, Staphylococcus
Staphylococcus
aureus and Streptococcus sanguinis and in Gram-positive soil bacterium Bacillus
Bacillus
subtilis.[19] Orthographic note[edit] The adjectives Gram-positive and Gram-negative derive from the surname of Hans Christian Gram; as eponymous adjectives, their initial letter can be either capital G or lower-case g, depending on which style guide (e.g., that of the CDC), if any, governs the document being written.[20] This is further explained at Gram staining § Orthographic note. References[edit]

^ a b Madigan, Michael T.; Martinko, John M. (2006). Brock Biology of Microorganisms (11th ed.). Pearson Prentice Hall. ISBN 0131443291.  ^ Gibbons, N. E.; Murray, R. G. E. (1978). "Proposals Concerning the Higher Taxa of Bacteria". International Journal of Systematic and Evolutionary Microbiology. 28 (1): 1–6. doi:10.1099/00207713-28-1-1.  ^ a b Woese, C. R. (1987). "Bacterial evolution". Microbiological Reviews. 51 (2): 221–271. PMC 373105 . PMID 2439888.  ^ a b c d e f g h Gupta, R. S. (1998). "Protein phylogenies and signature sequences: A reappraisal of evolutionary relationships among archaebacteria, eubacteria and eukaryotes". Microbiology
Microbiology
and Molecular Biology Reviews. 62: 1435–1491.  ^ a b c Gupta, R. S. (2000). "The natural evolutionary relationships among prokaryotes" (PDF). Critical Reviews in Microbiology. 26: 111–131. doi:10.1080/10408410091154219. PMID 10890353.  ^ a b Desvaux, M.; Hébraud, M.; Talon, R.; Henderson, I. R. (2009). "Secretion and subcellular localizations of bacterial proteins: A semantic awareness issue". Trends in Microbiology. 17: 139–145. doi:10.1016/j.tim.2009.01.004. PMID 19299134.  ^ a b Sutcliffe, I. C. (2010). "A phylum level perspective on bacterial cell envelope architecture". Trends in Microbiology. 18: 464–470. doi:10.1016/j.tim.2010.06.005. PMID 20637628.  ^ a b c d e Gupta, R. S. (1998). "What are archaebacteria: life's third domain or monoderm prokaryotes related to Gram-positive bacteria? A new proposal for the classification of prokaryotic organisms". Molecular Microbiology. 29 (3): 695–707. doi:10.1046/j.1365-2958.1998.00978.x. PMID 9723910.  ^ a b c d e f g Gupta, R. S. (2011). "Origin of diderm (gram-negative) bacteria: antibiotic selection pressure rather than endosymbiosis likely led to the evolution of bacterial cells with two membranes". Antonie van Leeuwenhoek. 100: 171–182. doi:10.1007/s10482-011-9616-8. PMC 3133647 . PMID 21717204.  ^ a b c Marchandin, H.; Teyssier, C.; Campos, J.; Jean-Pierre, H.; Roger, F.; Gay, B.; Carlier, J.-P.; Jumas-Bilak, E. (2009). "Negativicoccus succinicivorans gen. Nov., sp. Nov., isolated from human clinical samples, emended description of the family Veillonellaceae and description of Negativicutes classis nov., Selenomonadales ord. Nov. And Acidaminococcaceae fam. Nov. In the bacterial phylum Firmicutes". International Journal of Systematic and Evolutionary Microbiology. 60 (6): 1271–1279. doi:10.1099/ijs.0.013102-0. PMID 19667386.  ^ Yabe, S.; Aiba, Y.; Sakai, Y.; Hazaka, M.; Yokota, A. (2010). "Thermogemmatispora onikobensis gen. nov., sp. nov. And Thermogemmatispora foliorum sp. nov., isolated from fallen leaves on geothermal soils, and description of Thermogemmatisporaceae fam. Nov. And Thermogemmatisporales ord. Nov. Within the class Ktedonobacteria". International Journal of Systematic and Evolutionary Microbiology. 61 (4): 903–910. doi:10.1099/ijs.0.024877-0. PMID 20495028.  ^ Sutcliffe, I. C. (2011). " Cell envelope
Cell envelope
architecture in the Chloroflexi: A shifting frontline in a phylogenetic turf war". Environmental Microbiology. 13 (2): 279–282. doi:10.1111/j.1462-2920.2010.02339.x. PMID 20860732.  ^ Hugenholtz, P.; Tyson, G. W.; Webb, R. I.; Wagner, A. M.; Blackall, L. L. (2001). "Investigation of Candidate Division TM7, a Recently Recognized Major Lineage of the Domain Bacteria
Bacteria
with No Known Pure-Culture Representatives". Applied and Environmental Microbiology. 67 (1): 411–419. doi:10.1128/AEM.67.1.411-419.2001. PMC 92593 . PMID 11133473.  ^ Cavaletti, L.; Monciardini, P.; Bamonte, R.; Schumann, P.; Rohde, M.; Sosio, M.; Donadio, S. (2006). "New Lineage of Filamentous, Spore-Forming, Gram-Positive Bacteria
Bacteria
from Soil". Applied and Environmental Microbiology. 72 (6): 4360–4369. doi:10.1128/AEM.00132-06. PMC 1489649 . PMID 16751552.  ^ Gladwin, Mark; Trattler, Bill (2007). Clinical Microbiology
Microbiology
Made Ridiculously Simple. Miami, Florida: MedMaster. pp. 4–5. ISBN 978-0-940780-81-1.  ^ Sahebnasagh, R.; Saderi, H.; Owlia, P. (4–7 September 2011). Detection of methicillin-resistant Staphylococcus
Staphylococcus
aureus strains from clinical samples in Tehran by detection of the mecA and nuc genes. The First Iranian International Congress of Medical Bacteriology. Tabriz, Iran.  ^ MacDonald, Mhairi (2015). Avery's Neonatology: Pathophysiology and Management of the Newborn. Philadelphia: Wolters Kluwer. ISBN 9781451192681.  Access provided by the University of Pittsburgh. ^ a b c Johnston, C.; Martin, B.; Fichant, G.; Polard, P; Claverys, J. P. (2014). "Bacterial transformation: distribution, shared mechanisms and divergent control". Nature Reviews. Microbiology. 12 (3): 181–96. doi:10.1038/nrmicro3199. PMID 24509783.  ^ Michod, R. E.; Bernstein, H.; Nedelcu, A. M. (2008). "Adaptive value of sex in microbial pathogens". Infection, Genetics and Evolution. 8 (3): 267–85. doi:10.1016/j.meegid.2008.01.002. PMID 18295550.  ^ "Emerging Infectious Diseases Journal Style Guide". CDC.gov. Centers for Disease Control and Prevention. 

External links[edit]

 This article incorporates public domain material from the NCBI document "Science Primer". 3D structures of proteins associated with plasma membrane of Gram-positive bacteria 3D structures of proteins associated with outer membrane of Gram-positive bacteria

v t e

Microbiology: Bacteria

Medical microbiology

infection Coley's toxins Exotoxin Lysogenic cycle Pathogenic bacteria resistance

Biochemistry and ecology

Oxygen preference

Aerobic

Obligate

Anaerobic

Facultative Obligate

Microaerophile Nanaerobe Aerotolerant

Other

Extremophile Human flora

Gut Lung Mouth Skin Vaginal (In pregnancy) Placental Uterine Salivary

Microbial metabolism Nitrogen fixation Microbial ecology Primary nutritional groups Substrate preference

Lipophilic Saccharophilic

Shape

Bacterial cellular morphologies Coccus

Diplococcus

Bacillus Coccobacillus Spiral

Structure

Cell envelope

Cell membrane Cell wall: Peptidoglycan

NAM NAG DAP

Gram-positive bacteria
Gram-positive bacteria
only: Teichoic acid Lipoteichoic acid Endospore Gram-negative bacteria
Gram-negative bacteria
only: Bacterial outer membrane

Porin Lipopolysaccharide

Periplasmic space Mycobacteria only: Arabinogalactan Mycolic acid

Outside envelope

Bacterial capsule Slime layer S-layer Glycocalyx Pilus Fimbria Non-motile bacteria

Composite

Biofilm

Taxonomy

Bacteria
Bacteria
(classifications) Bacterial phyla Former groupings: Schizomycetes Monera Prokaryota

Gracilicutes Firmicutes Mollicutes Mendosicutes

v t e

Prokaryotes: Bacteria
Bacteria
classification (phyla and orders)

Domain Archaea Bacteria Eukaryota (Supergroup Plant Hacrobia Heterokont Alveolata Rhizaria Excavata Amoebozoa Opisthokonta

Animal Fungi)

G-/ OM

Terra-/ Glidobacteria (BV1)

Eobacteria

Deinococcus–Thermus

Deinococcales Thermales

Chloroflexi

Anaerolineales Caldilineales Chloroflexales Herpetosiphonales Dehalococcoidales Ktedonobacterales Thermogemmatisporales Thermomicrobiales Sphaerobacterales

other glidobacteria

Thermodesulfobacteria thermophiles

Aquificae Thermotogae

Cyanobacteria

Proteobacteria (BV2)

Alpha

Caulobacterales Kiloniellales Kordiimonadales Magnetococcales Parvularculales Rhizobiales Rhodobacterales Rhodospirillales Rickettsiales Sneathiellales Sphingomonadales

Beta

Burkholderiales Hydrogenophilales Methylophilales Neisseriales Nitrosomonadales Procabacteriales Rhodocyclales

Gamma

Acidithiobacillales Aeromonadales Alteromonadales Cardiobacteriales Chromatiales Enterobacteriales Legionellales Methylococcales Oceanospirillales Orbales Pasteurellales Pseudomonadales Salinisphaerales Thiotrichales Vibrionales Xanthomonadales

Delta

Bdellovibrionales Desulfarculales Desulfobacterales Desulfovibrionales Desulfurellales Desulfuromonadales Myxococcales Syntrophobacterales Syntrophorhabdales

Epsilon

Campylobacterales Nautiliales

Zeta

Mariprofundales

BV4

Spirochaetes

Spirochaetes

Sphingobacteria (FCB group)

Fibrobacteres Chlorobi

Chlorobiales Ignavibacteriales

Bacteroidetes

Bacteroidales Cytophagales Flavobacteriales Sphingobacteriales

Planctobacteria/ (PVC group)

Chlamydiae Lentisphaerae

Lentisphaerales Oligosphaerales Victivallales

Planctomycetes

Phycisphaerales Planctomycetales

Verrucomicrobia

Puniceicoccales Opitutales Chthoniobacterales Verrucomicrobiales

"Poribacteria"

Other GN

Acidobacteria

Acidobacteriales Acanthopleuribacterales Holophagales Solibacterales

Armatimonadetes

Armatimonadales Chthonomonadales Fimbriimonadales

Caldiserica Chrysiogenetes Deferribacteres Dictyoglomi Elusimicrobia Fusobacteria Gemmatimonadetes Nitrospirae Synergistetes

G+/ no OM

Firmicutes (BV3)

Bacilli

Bacillales Lactobacillales

Clostridia

Clostridiales Halanaerobiales Thermoanaerobacteriales Natranaerobiales

Erysipelotrichia

Erysipelotrichiales

Thermolithobacteria

Thermolithobacterales

Tenericutes/ Mollicutes

Mycoplasmatales Entomoplasmatales Anaeroplasmatales Acholeplasmatales Haloplasmatales

Negativicutes

Selenomonadales

Actinobacteria (BV5)

Actinobacteria

Actinomycetales Bifidobacteriales

Acidimicrobiia

Acidimicrobiales

Coriobacteriidae

Coriobacteriales

Nitriliruptoria

Euzebyales Nitriliruptorales

Rubrobacteria

Gaiellales Rubrobacterales Thermoleophilales Solirubrobacterales

Incertae sedis

†Archaeosphaeroides †Eobacterium †Leptotrichites

Source: Bergey's Manual (2001–2012). Alternative views: Wikispecies.

v t e

Firmicutes
Firmicutes
(low-G+C) Infectious diseases Bacterial diseases: G+

primarily A00–A79, 001–041, 080–109

Bacilli

Lactobacillales (Cat-)

Streptococcus

α

optochin susceptible

S. pneumoniae

Pneumococcal infection

optochin resistant

Viridans streptococci: S. mitis S. mutans S. oralis S. sanguinis S. sobrinus milleri group

β

A

bacitracin susceptible: S. pyogenes

Group A streptococcal infection Streptococcal pharyngitis Scarlet fever Erysipelas Rheumatic fever

B

bacitracin resistant, CAMP test+: S. agalactiae

Group B streptococcal infection

ungrouped

Streptococcus
Streptococcus
iniae

Cutaneous Streptococcus
Streptococcus
iniae infection

γ

D BEA+: Streptococcus
Streptococcus
bovis

Enterococcus

BEA+: Enterococcus
Enterococcus
faecalis

Urinary tract infection

Enterococcus
Enterococcus
faecium

Bacillales (Cat+)

Staphylococcus

Cg+

S. aureus

Staphylococcal scalded skin syndrome

Toxic shock syndrome MRSA

Cg-

novobiocin susceptible

S. epidermidis

novobiocin resistant

S. saprophyticus

Bacillus

Bacillus
Bacillus
anthracis

Anthrax

Bacillus
Bacillus
cereus

Food poisoning

Listeria

Listeria
Listeria
monocytogenes

Listeriosis

Clostridia

Clostridium
Clostridium
(spore-forming)

motile:

Clostridium
Clostridium
difficile

Pseudomembranous colitis

Clostridium
Clostridium
botulinum

Botulism

Clostridium
Clostridium
tetani

Tetanus

nonmotile:

Clostridium
Clostridium
perfringens

Gas gangrene Clostridial necrotizing enteritis

Peptostreptococcus
Peptostreptococcus
(non-spore forming)

Peptostreptococcus
Peptostreptococcus
magnus

Mollicutes

Mycoplasmataceae

Ureaplasma urealyticum

Ureaplasma infection

Mycoplasma
Mycoplasma
genitalium Mycoplasma
Mycoplasma
pneumoniae

Mycoplasma
Mycoplasma
pneumonia

Anaeroplasmatales

Erysipelothrix rhusiopathiae

Erysipeloid

.