Cell Envelope Formation and Function

Little is known of the ways of biosynthesis and insertion in the membranes of PolyP-PHB-Ca2+ complexes. In polyphosphate kinase 1 mutants of E. coli, the amounts of the complexes did not change (Castuma et al., 1995). Therefore, the PolyP in the complexes is synthesized not by polyphosphate kinase 1 but by another enzyme. E. coli strain, which lacks the AcrA component of a major multi-drug resistance pump, had greatly reduced amounts of the complexes and was defective in its ability to maintain sub-micromolar levels of free Ca2+ in the cytoplasm (Jones et al., 2003). This indicates that the AcrAB transporter may have a novel, hitherto undetected, physiological role, either directly in the membrane assembly of the PHB complexes or the transport of a component of the membrane, which is essential for assembly of the complexes into the membrane. 

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In conclusion, it should be noted that PolyPs are polyfunctional compounds. Their most important functions are as follows phosphate and energy reservation, sequestration and storage of cations, formation of membrane channels, participation in phosphate transport, involvement in cell-envelope formation and function, gene activity control, regulation of enzyme activities, and, as a result, an important role in stress response and stationary-phase adaptation. 

The cell envelopes of bacteria play an essential role in bacterial virulence, surface attachment and biofilm formation (O Toole et al, 2000). This cell compartment possesses PolyPs, and thereby its role in the above functions was intensively investigated. The conclusion was... 

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