There are a number of bacteria that lack capsule. In the respiratory tract and oral cavity there are several species without capsular material on their surface. Examples are most Gram-negative Haemophilus influenza strains are unencapsulated (or non-typeable). Also, increasing numbers of non-encapsulated Streptococcus pneumoniae are seen after the introcution of the conjugate vaccine 2000. In the oral cavity most streptococci (Streptococcus oralis, gordoniii etc) are unencapsulated.

The advantage would be that they require less energy use to produce the capsule and can use that energy for other things. Instead they either "hide" in complex biofilms with other organisms that produce capsule or polysaccharide matrix or they produce surface proteins that are antiphagocytic as one way to protecting themselves. Those are some examples and there are many more.

Hi Paolo,

most bacteria contain a capsule or some sort of surface polysaccharide you can call a capsule or capsule-like ; you'll find hundreds of reviews and textbook chapters on the topic while surfing Pubmed and Internet.

The best (and to my knowledge nearly only example) of bacteria that lack a cell wall, and a capsule, are mycoplasma, or at least some species of mycoplasma.

Best,

Olivier

An advantage for the Mycoplasma could be the application of antibiotics, triggering the cell wall byosynthesis pathway. That's why when you get a Mycoplasma contamination of your cell cultures treatment with Penicillin/Streptamycin does not inhibit Mycomplasma growth. In addition, so called L-forms, which are missing a cell wall, are present in many Gram-positive and Gram-negative species.

There are a number of bacteria that lack capsule. In the respiratory tract and oral cavity there are several species without capsular material on their surface. Examples are most Gram-negative Haemophilus influenza strains are unencapsulated (or non-typeable). Also, increasing numbers of non-encapsulated Streptococcus pneumoniae are seen after the introcution of the conjugate vaccine 2000. In the oral cavity most streptococci (Streptococcus oralis, gordoniii etc) are unencapsulated.

The advantage would be that they require less energy use to produce the capsule and can use that energy for other things. Instead they either "hide" in complex biofilms with other organisms that produce capsule or polysaccharide matrix or they produce surface proteins that are antiphagocytic as one way to protecting themselves. Those are some examples and there are many more.

Almost all Mycoplasma species produce a capsule. I would argue that in cases where no capsule is seen, either it has not been identified yet or it is regulated and simply shut off.

Also, many heavily encapsulated bacteria isolated from clinical samples (or grown in chambers in vivo), lose their capsule when grown in broth or on agar in vitro.

As mentioned above, capsule is a virulence factor and also an acquired trait (transformation, conjugation, etc) it may or may not be expressed under certain conditions, encapsulated clinical isolates get comfortable after a few passes during in vitro cultures and they don't receive signals from the environment saying they are in danger of being phagocytized, so they save energy by not expressing the capsule.

As for examples, you can find strains in many species that have capsule or not, Staph aureus, Kleb pneumoniae, Strep pneumoniae, etc ... go to http://www.ncbi.nlm.nih.gov/ and do a quick search you will find lot's of references.

Considering I work on Mycoplasma pneumoniae and other Mycoplasma species studing the glycocaylx, I can assure you that Mycoplasma species do produce exopolysaccharides (you can check our recent publications for data). In the case of M. pneumoniae, the causative agent of atypical pneumonia in humans, this species produces at least two exopolysaccharides. A capsule (or slime-layer) like polymer composed of glucose and galactose, similar to the galactan produced by Mycoplasma mycoides or the glucose-galctose polymer produced by Mycoplasma pulmonis. and an N-acetyl glucosamine and galactose adhesive polymer that is associated with biofilm formation.

Group A streptococcus (GAS) causes human pharyngitis and invasive infections and frequently colonizes individuals asymptomatically. Lack Genes Required for Hyaluronic Acid Capsule Biosynthesis. Probabily they have alternative, compensatory mechanisms that promote virulence.

Not, all the bacteria are not capsuled. There is a great number of bacteria implied in human pathologies and which are not capsuled. Among the enterobacteries not having capsules one can quote : Pseudomonas aeruginosa, Shiguelles, Vibrio cholerae which are gram negative bacteria. In the family of Neisseriaceae one can quote Haemophilus ducrey and H. aegyptius which are also gram negative bacilli and which are not capsuled. The bacteria which are known to have capsule are Streptocoque pneumoniae and Klebsielles. The remainder of the bacteria only are often capsuled.

All bacteria have a slime layer on their surfaces and when visible under the microscope, they are reffered to as capsule. In a sense, if bacteria are in it's natural habitat in the animal tissue, the capsule is visible under microscope. I believe, the statement that all bacteria have capsule is not correct unless it is microscopically visible. This understanding helps in rapid identification of a bacterium in clinical specimens for routine diagnostic purposes.

Dr. H. N. Madhavan. Md. PhD., FAMS., FIC Path

A classic example of encapsulated vs non-encapsulated bacteria, even within the same genera, is Neisseria. N. gonorrhoreae never produces a capsule(it does not possess the capsular biosynthetic genes ) whereas N. meningitidis is almost always found with a capsule, the only circumstances where it is not found with it's capsule is when the capsular biosynthetic genes have been switched off by phase variation (imparts a fitness advantage in some of the later stages of infection)

Most of Gram positive bacteria do not have so called capsules. Exo polysaccharide (EPS) or polypeptide capsules are mostly property of Gram negative bacteria even though some Gram positive bacteria may display capsules. As Gram positive out layer is much thicker than Gram negative it usually does not require another protective layer as it would be just waste of energy for the bacteria.

There are a vast number of non-encapsulated bacteria of all classes. Escherichia coli varies (K antigen in serotyping) in presence or absence from strain to strain. Salmonella enterica lacks a capsule with the notable exception of servovar Typhi (and a few isolates of serovar Dublin). The capsule in S. Typhi is considered important in avoiding the massive inflammatory response Salmonella elicits in the gut-hence it is considered a 'stealth pathogen'.

No not all have a capsule and in many cases a capsule is detrimental to virulence during certain parts of the bacterial lifecycle. Neisseria gonorrhoeae, a Gram negative obligate intra-cellular pathogen, lacks capsular synthetic genes and never produce a capsule while its close relative Neisseria meningitidis possess these genes. The meningococci however use a mechanism known as "phase variation" to switch these genes off in some of its progeny. This ensures that at any one time there are a certain number of progeny bacteria not expressing the capsule, a characteristic which is very important for certain processes such host cell adhesion when the capsule may block surface adhesion molecules. This sub-population then amplifies via clonal expansion to become the majority population. Again a certain sub-population of these will be expressing the capsular genes which means that when the bacteria then moves into its new environment the encapsulated population will again expand. The encapsulated population will again become the major population which is important to ensure immune evasion by fact of the capsule hiding any immunogenic surface structures such as the adhesions mentioned already.

NO. not all bacteria has capsule.

capsular bacteria best example is S.pneumonia causing Pneumonia

capsule is advantagious in escaping immune system. as capsule is a slime and escapes phagocytosis by macrophages.