Can S-Layers of Bacillaceae Control the Release of Their Own Exoproteins ?
Crystalline bacterial cell surface layers (S-layers) represent the outermost cell wall component in many strains of gram-positive and gram-negative eubacteria and have been observed during all states of growth and division (for recent review see Messner and Sleytr, 1992). High-resolution electron microscopy and permeability studies on isolated S-layers revealed a pore size in the range of 4 nm for most of the Bacillus species, which corresponds to a molecular weight cut-off of approximately 45000 Da (Sara and Sleytr, 1987). Many gram-positive eubacteria are able to produce enzymes like amylases, proteases or cellulases which are released into the culture fluid. Such bacteria as those of the genus Bacillus have frequently been the organisms of choice with regard to the commercial production of large quantities of extracellular enzymes (Priest, 1989). The amylases secreted by different Bacillus species have been shown to have M,s in the range of 55000 to 60000, but these can be synthesized as larger precursors with Mr up to 130000 (Uozumi et al., 1989). Because the molecular weights of the majority of extracellular proteins are just within the range of the molecular weight cut-off of the S-layers of the Bacillaceae, the question arises how these proteins can be efficiently exported by S-layer carrying strains. In the present study, the size of the exported amylases, as well as the molecular weight cut-off of the S-layer was determined for Bacillus polymyxa CCM 1459.
KeywordsSugar Permeability Starch Electrophoresis Bacillus
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- Priest, F.G., 1989, Products and applications, in: “Bacillus Biotechnology Handbook 2,” C.R. Harwood, ed., Plenum Press, New York.Google Scholar