Bacteria, attachment probabilities

The initial event in the pathogenesis of most bacterial infections is the attachment of the bacteria to the mucosal surface. This probably occurs by a receptor mechanism that exhibits a high degree of cellular specificity. Capsular polysaccharides have not been implicated in this... 

The protein chain grows in a particular direction, so that the first amino acid of the sequence has a free NH2 group whilst the last amino acid has a free COOH. Experiments have shown that in most cases the N-terminal amino acid is methionine. So Met-t-RNA would seem to be the initiator. But methionine can also be inserted at other positions in the chain, so how does Met-t-RNA know where to place its amino acid It is not codon directed, as there is, it is apparent from Figure 23, only one trinucleotide sequence corresponding to methionine, the AUG triplet. In bacteria at least (in which most of these experiments have been carried out), it seems that to serve as an initiator, the methionine must be converted to the unusual amino acid formyl-methionine for attachment to the P site. It seems probable that a similar mechanism exists in mammalian cells although the position here is not yet completely clear. 

Probably the most important factor in the attachment of bacteria is the bacterial surface itself, although this is difficult to characterise [Fletcher et al 1983]. There is considerable variation between bacteria and this is due, at least in part to the differences in composition of cell surface polymers [Neufeld et al 1980]. 

The release into the effluent of identiflable particles, with settling characteristics similar to those of typical effluent particles, permits the monitoring of the temporal and spatial dispersion of the effluent particulates. There have been no previous attempts to label and trace particulates from the Southern California municipal waste outfalls. Bacteria from the outfalls have been traced but their dispersion behavior is unknown since they probably attach to uncharacterized surfaces. 

When phytoplankton cells die for some reason (e.g. lysis) the soluble components will leave the cell to the external medium. The insoluble cellular material left has a relatively high chemical stability, but degradation may be greatly enhanced by enzymatically catalyzed reactions. Where are enzymes located It seems less probable to find active enzymes suspended in sea water - most of them are extracellular enzymes located on the bacterial cell surface [71 ]. Active bacteria are partly free hving in the water and partly attached to phytoplankton cells [71-73]. 

There are only a few studies dealing with the cellular uptake of orotic acid. The incorporation of orotic acid into whole cells can be stimulated more than 90-fold by a combination of PRPP and a heat labile factor [150], probably orotate phosphoribosyltransferase. It is assumed [151] that the enzyme attaches to the cell membrane and in the presence of external orotic acid and PRPP leads to the formation of internal orotidine 5 -phosphate. In bacteria the orotate is taken up similarly [151] by a process of group translocation across the membrane involving the participation of orotate phospjioribosyltransferase and requiring PRPP. 

ATPases are intimately involved with energy transduction in biological membranes. They catalyse the synthesis of ATP in the final stage of oxidative phosphorylation. Alternatively, they can utilize ATP to drive the translocation of Na and K [203]. In bacteria, ATPases are also found in association with the cell membrane, and in some cases appear as stalked particles attached to the membrane [16]. They are probably also involved in the production of ATP by oxidative phosphorylation in aerobic organisms [204,205] and in ion transport [123]. 

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