V. Functions of S-layers

Abstract

Although S-layers are being increasingly identified on Bacteria and Archaea, it is enigmatic that in most cases S-layer function continues to elude us. In a few instances, S-layers have been shown to be virulence factors on pathogens (e.g. Campylobacter fetus ssp. fetus and Aeromonas salmonicida), protective against Bdellovibrio, a depository for surface-exposed enzymes (e.g. Bacillus stearothermophilus), shape-determining agents (e.g. Thermoproteus tenax) and nucleation factors for fine-grain mineral development (e.g. Synechococcus GL 24). Yet, for the vast majority of S-layered bacteria, the natural function of these crystalline arrays continues to be evasive. The following review up-dates the functional basis of S-layers and describes such diverse topics as the effect of S-layers on the Gram stain, bacteriophage adsorption in lactobacilli, phagocytosis by human polymorphonuclear leukocytes, the adhesion of a high-molecular-mass amylase, outer membrane porosity, and the secretion of extracellular enzymes of Thermoanaerobacterium. In addition, the functional aspect of calcium on the Caulobacter S-layer is explained.

S-layer protein production by Corynebacterium strains is dependent on the carbon source

“…It is commonly found in the soil (Trautwetter & Blanco, 1988) and organic acids may be its principal substrates. The S-layer may therefore be associated with adhesion sites for exoenzymes, surface recognition and cell adhesion to substrates, as has been suggested for the S-layers of several other organisms (Beveridge et al, 1997). We showed, using a lacZ fusion, that PS2 production was mainly regulated by changes in cspB gene expression and that secretion was probably not a limiting step in PS2 accumulation at the cell surface.…”

The surface (S)-layer gene cspB of Corynebacterium glutamicum is transcriptionally activated by a LuxR-type regulator and located on a 6 kb genomic island absent from the type strain ATCC 13032

“…The current lack of knowledge about the function of the C. glutamicum S-layer makes it difficult to relate the loss of the S-layer locus to the fitness of this bacterium. C. glutamicum is commonly found in soil, and the S-layer might be associated with adhesion of exoenzymes and substrates or with other surface recognition processes (Beveridge et al, 1997). However, the loss of the S-layer locus might simply be the result of prolonged cultivation of the type-strain on synthetic medium since its discovery in 1957 and of its extensive use in the fermentation industry (Hermann, 2003;Sleytr & Sara, 1997).…”

Interaction of the Crystalline Bacterial Cell Surface Layer Protein SbsB and the Secondary Cell Wall Polymer of Geobacillus stearothermophilus PV72 Assessed by Real-Time Surface Plasmon Resonance Biosensor Technology

“…Affinity studies revealed that SLH domains mediate binding of S-layer proteins, as well as cell-associated exoenzymes and exoproteins, to the rigid cell wall layer in gram-positive bacteria (2,3,5,9,12,18,24). In S-layer proteins, typically three SLH motifs were found in the amino-terminal region and there is strong evidence that secondary cell wall polymers (SCWPs) rather than peptidoglycan itself serve as anchoring structures for SLH domains (2,3,5,12,18,24,25,34,39).In the present report, the nature of the basic interaction in the mechanism anchoring an S-layer protein to the rigid cell wall layer was systematically investigated by real-time surface plasmon resonance (SPR) biosensor technology. For that purpose, S-layer protein SbsB and the corresponding SCWP of Geobacillus stearothermophilus PV72/p2 (formerly Bacillus stearothermophilus PV72/p2) (29), an oxygen-induced variant strain of G. stearothermophilus PV72/p6 (38), were used as a model system.…”