Bacterial capsules

Capsule (bacterial) a loose, more or less amorphous layer made up of organic polymers, which is deposited outside, and remains attached to, the cell wall. 

Some bacterial species accumulate material as a coating of varying degrees of looseness. If the material is reasonably discrete it is called a capsule, if loosely bound to the surface it is called slime. 

An abscess occurs if peritoneal contamination is localized but bacterial elimination is incomplete. The location of the abscess often is related to the site of primary disease. For example, abscesses resulting from appendicitis tend to appear in the right lower quadrant or the pelvis those resulting from diverticulitis tend to appear in the left lower quadrant or pelvis. A mature abscess may have a fibrinous capsule that isolates bacteria and the liquid core from antimicrobials and immunologic defenses. 

Polysaccharides occur (1) in cell walls, (2) extracellularly in capsules and gums, and (3) inside of bacterial cells. The first two have already been discussed. 

A common characteristic of most CNS bacterial pathogens (e.g., H. influenzae, Escherichia coli, and N. meningitidis) is the presence of an extensive polysaccharide capsule that is resistant to neutrophil phagocytosis and complement opsonization. 

Pharmaceutical preparations are drugs formulated and fabricated into their final form for direct consumption (tablets, capsules, etc.). The industry has grown rapidly in the past 30 years especially in pharmaceutical production. Examples of biological products are bacterial and virus... 

Work at the EPA Gulf Breeze Laboratory has demonstrated the potential usefulness of encapsulation in the bioremediation of PAHs. A model system has been developed in which a pure culture capable of degrading fluoranthene (strain EPA505) has been successfully encapsulated in polyurethane foam and polyvinyl alcohol (Baker et al., 1988). The capsules can be stored for several months at 4 °C with only minimal loss of viability. Upon addition of the capsules to moist soil, fluoranthene mineralization commenced in approximately the same way as observed when fresh bacterial cells were added to the soil. These results are shown in Figure 5.7a. Since the same inoculation size was used in all flasks during this experiment, the results suggest that the immobilization process does not significantly affect microbial activity. 

The immediate cause of the ropy or slimy condition is the bacterial formation of gums or mucins by bacteria. Gums are the more common cause. These are probably galactans produced by fermentation of lactose. Some of the active peptonizing bacteria produce sliminess by formation of mucins, which are combinations of proteins with a carbohydrate radical. Development of sliminess is closely associated with capsule formation (Hammer 1930). 

Its chemical makeup is considered in Chapter 8. One of the layers is often referred to as the outer membrane. In some bacteria the wall may be as much as 80 nm thick and may be further surrounded by a thick capsule or glycocalyx (slime layer).13 The main function of the wall seems to be to prevent osmotic swelling and bursting of the bacterial cell when the surrounding medium is hypotonic. 

Other bacterial coats. Archaebacteria not only have unusual plasma membranes that contain phytanyl and diphytanyl groups (Section A,3)608 but also have special surface layers (S-Iayers) that may consist of many copies of a single protein that is anchored in the cell membrane.609 The surface protein of the hypothermic Staphylothermus marius consists of a complex structure formed from a tetramer of 92-kDa rods with an equal number of 85-kDa "arms."610 611 S-layers are often formed not only by archaebacteria but also by eubacteria of several types and with quite varied structures.612 14 While many bacteria carry adhesins on pili, in others these adhesive proteins are also components of surface layers.615 Additional sheaths, capsules, or slime layers, often composed of dextrans (Chapter 4) and other carbohydrates, surround some bacteria. 

UDP-GlcNAc can be converted to UDP-N-acetyl-mannosamine (UDP-ManNAc) with concurrent elimination of UDP (Eq. 20-7). , 7b This unusual epimeri-zation occurs without creation of an adjacent carbonyl group that would activate the 2-H for removal as a proton. As indicated by the small arrows in Eq. 20-7, step a, the UDP is evidently eliminated. In a bacterial enzyme it remains in the E-S complex and is returned after a conformational change involving the acetamido group. This allows the transient C1-C2 double bond to be protonated from the opposite side (Eq. 20-7, step a).47 In bacteria the UDP-ManNAc may be dehydrogenated to UDP-N-acetylmannos-aminuronic acid (ManNAcA). Both ManNAc and ManNAcA are components of bacterial capsules.47... 

The pH of the colon varies depending on the type of food ingested. In general, a drop in pH to 5.5 6.5 is monitored when a radiotelemetric capsule enters the colon [85,86]. This pH drop is caused by acidification of the colonic contents by bacterial fermentation (Table 1.1). 

The influence of NO in thrombogenesis, bacterial infection, angiogenesis, and the immune response suggest that its active release into the tissue surrounding a sensor may minimize the FBR. Sensor coatings that release NO could reduce the occurrence and severity of bacterial infection, minimize inflammation and collagen capsule formation, and promote the formation of new blood vessels, all of which would create a more favorable implant environment. Since NO is reactive (i.e., has a short half-life), the effects of NO would remain localized to the area from which it is released. 

For a time, the question of the bacterial origin of these bodies was hotly debated. Hanks,208 from cytological evidence and the fact that such materials were confined to the leprosy bacillus and disappeared during sulfone therapy, persuasively reasoned that they originated in M. leprae. Moreover, since chloroform in aqueous systems declumped and dispersed M. leprae, he concluded that mycobacterial lipids were the major bonding substances in the electron-transparent material. Since the material of the capsule can be stained with Sudan Black B, Fisher and Barksdale209 and Nishiura et al.2 0 had concluded that the electron-transparent zone which surrounds M. leprae in vivo is lipid. 

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