Bacterial capsule

capsulecapsulesPolysaccharide encapsulated bacteriaencapsulatedcapsulatedbacterial capsulescapsularencapsulated bacteriacapsular polysaccharideencapsulated organisms
The bacterial capsule is a very large structure of many bacteria.wikipedia
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Gram-positive bacteria

Gram-positiveGram positivegram-positive bacterium
The capsule—which can be found in both gram negative and gram-positive bacteria—is different from the second lipid membrane – bacterial outer membrane, which contains lipopolysaccharides and lipoproteins and is found only in gram-negative bacteria.
Only some species have a capsule, usually consisting of polysaccharides.

Cell envelope

bacteriabacterial cell wall and plasma membranebacterial envelope
It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell.
Either type may have an enclosing capsule of polysaccharide for extra protection.

Bacteria

bacteriumbacterialEubacteria
The bacterial capsule is a very large structure of many bacteria.
Glycocalyx is produced by many bacteria to surround their cells, and varies in structural complexity: ranging from a disorganised slime layer of extracellular polymeric substances to a highly structured capsule.

Bacillus anthracis

B. anthracisanthraxanthrax bacteria
It usually consists of polysaccharides, but can be composed of other materials such as glycoprotein, polypeptide D-glutamic acid in B. anthracis, and peptidoglycan and muramic acid found in E.coli bacterial capsule.
It is one of few bacteria known to synthesize a protein capsule (poly-D-gamma-glutamic acid).

Klebsiella pneumoniae

K. pneumoniaeKlebsiella rhinoscleromatisK. pneumonia
Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium.

Pseudomonas aeruginosa

P. aeruginosaPseudomonasPseudomonas aeruginosa'' infection
Pseudomonas aeruginosa is a common encapsulated, Gram-negative, rod-shaped bacterium that can cause disease in plants and animals, including humans.

Glycocalyx

glycocalix
Capsule and slime layer are sometimes summarized under the term glycocalyx.
A distinct, gelatinous glycocalyx is called a capsule, whereas an irregular, diffuse layer is called a slime layer.

Hyaluronic acid

hyaluronanhyaluronateHyalgan
Hyaluronic acid is also a component of the group A streptococcal extracellular capsule, and is believed to play a role in virulence.

Streptococcus pyogenes

S. pyogenesgroup A streptococcusgroup A beta-hemolytic ''Streptococcus
Capsules too small to be seen with an ordinary microscope, such as the M protein of Streptococcus pyogenes, are called microcapsules.
A carbohydrate-based bacterial capsule composed of hyaluronic acid surrounds the bacterium, protecting it from phagocytosis by neutrophils.

Slime layer

capsular slime
When the amorphous viscid secretion (that makes up the capsule) diffuses into the surrounding medium and remains as a loose undemarcated secretion, it is known as a slime layer.
A bacterial capsule is similar

Streptococcus agalactiae

Group B StreptococcusS. agalactiaegroup B streptococci
GBS is surrounded by a bacterial capsule composed of polysaccharides (exopolysacharide).

Polysaccharide

polysaccharidesheteropolysaccharidecomplex carbohydrates
It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It usually consists of polysaccharides, but can be composed of other materials such as glycoprotein, polypeptide D-glutamic acid in B. anthracis, and peptidoglycan and muramic acid found in E.coli bacterial capsule.

Quellung reaction

Quellungserological typing
The Quellung reaction, also called the Neufeld reaction, is a biochemical reaction in which antibodies bind to the bacterial capsule of Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Bacillus anthracis, Haemophilus influenzae, Escherichia coli, and Salmonella.

Neisseria meningitidis

meningococcusN. meningitidismeningococcal
Vaccination using capsular material is effective against some organisms (e.g., H. influenzae type b, S. pneumoniae, and N. meningitidis ).
Other virulence factors include a polysaccharide capsule which prevents host phagocytosis and aids in evasion of the host immune response; fimbriae mediate attachment of the bacterium to the epithelial cells of the nasopharynx.

Streptococcus pneumoniae

pneumococcusS. pneumoniaepneumococcal
Vaccination using capsular material is effective against some organisms (e.g., H. influenzae type b, S. pneumoniae, and N. meningitidis ).
The encapsulated, Gram-positive, coccoid bacteria have a distinctive morphology on Gram stain, lancet-shaped diplococci.

Bacterial cell structure

bacterial cellscell wallbacterial cell wall
Capsules are relatively impermeable structures that cannot be stained with dyes such as India ink.

Gram-negative bacteria

Gram-negativeGram negativeGram-negative bacterium
The capsule—which can be found in both gram negative and gram-positive bacteria—is different from the second lipid membrane – bacterial outer membrane, which contains lipopolysaccharides and lipoproteins and is found only in gram-negative bacteria.

Bacterial outer membrane

outer membraneouter membranesouter bacterial membrane
The capsule—which can be found in both gram negative and gram-positive bacteria—is different from the second lipid membrane – bacterial outer membrane, which contains lipopolysaccharides and lipoproteins and is found only in gram-negative bacteria.

Lipopolysaccharide

endotoxinLPSlipopolysaccharides
The capsule—which can be found in both gram negative and gram-positive bacteria—is different from the second lipid membrane – bacterial outer membrane, which contains lipopolysaccharides and lipoproteins and is found only in gram-negative bacteria.

Lipoprotein

lipoproteinsAlpha 1-lipoproteinAlpha 2-lipoprotein
The capsule—which can be found in both gram negative and gram-positive bacteria—is different from the second lipid membrane – bacterial outer membrane, which contains lipopolysaccharides and lipoproteins and is found only in gram-negative bacteria.

Peptide

polypeptidepeptidespolypeptides
It usually consists of polysaccharides, but can be composed of other materials such as glycoprotein, polypeptide D-glutamic acid in B. anthracis, and peptidoglycan and muramic acid found in E.coli bacterial capsule.

Glutamic acid

glutamateL-glutamateGlu
It usually consists of polysaccharides, but can be composed of other materials such as glycoprotein, polypeptide D-glutamic acid in B. anthracis, and peptidoglycan and muramic acid found in E.coli bacterial capsule.

Virulence factor

virulence factorsfactorsimmunoevasive
The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis).

Phagocytosis

phagocyticphagocytosedphagocytose
The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis).

Water

H 2 OHOliquid water
Capsules also contain water which protects the bacteria against desiccation.