IV. Molecular biology of S-layers

Abstract

In this chapter we report on the molecular biology of crystalline surface layers of different bacterial groups. The limited information indicates that there are many variations on a common theme. Sequence variety, antigenic diversity, gene expression, rearrangements, influence of environmental factors and applied aspects are addressed. There is considerable variety in the S-layer composition, which was elucidated by sequence analysis of the corresponding genes. In Corynebacterium glutamicum one major cell wall protein is responsible for the formation of a highly ordered, hexagonal array. In contrast, two abundant surface proteins from the S-layer of Bacillus anthracis. Each protein possesses three S-layer homology motifs and one protein could be a virulence factor. The antigenic diversity and ABC transporters are important features, which have been studied in methanogenic archaea. The expression of the S-layer components is controlled by three genes in the case of Thermus thermophilus. One has repressor activity on the S-layer gene promoter, the second codes for the S-layer protein. The rearrangement by reciprocal recombination was investigated in Campylobacter fetus. 7-8 S-layer proteins with a high degree of homology at the 5' and 3' ends were found. Environmental changes influence the surface properties of Bacillus stearothermophilus. Depending on oxygen supply, this species produces different S-layer proteins. Finally, the molecular bases for some applications are discussed. Recombinant S-layer fusion proteins have been designed for biotechnology.

O-Acetylation of Peptidoglycan Is Required for Proper Cell Separation and S-layer Anchoring in Bacillus anthracis

“…However, as noted above, this bacterium does produce an S-layer, an additional cell wall component composed of self-assembled proteins that encapsulates the cell. The major components of the S-layer, the Sap and EA1 proteins, are anchored to the cell wall using a secondary polysaccharide and are required for cell separation (22,23).…”

A temperature‐sensitive expression system based on the Geobacillus stearothermophilus NRS 2004/3a sgsE surface‐layer gene promoter

“…Two-dimensional crystalline S-layers (surface layers), representing the outermost cell envelope layer of bacteria from all major phylogenetic groups, exist as a regular, closed lattice on the bacterial surface [1,2]. S-layer proteins are among the most abundant cellular proteins, indicating that these metabolically expensive compounds must indeed play a pivotal role in bacterial life.…”

“…All promoter regions described for S-layer genes have so far revealed the conserved hexanucleotide −10 and −35 regions typical of prokaryotic promoters. Studies in various organisms have provided clues to the mechanisms underlying S-layer gene regulation [2]. Frequently, multiple and tandemly arranged promoters are present upstream of S-layer genes [6][7][8][9].…”

Cyanobacteria as Biocatalysts for Carbonate Mineralization

“…However, S-layer structures and S-layer-encoding genes were identified in many other Gram-negative bacteria, including species of Aeromonas, Campylobacter, Caulobacter, Fusobacterium, Thermus etc. [105,106]. Also, more than 60 cultivated strains of cyanobacteria are known to possess an S-layer [98], most of which are of p6 lattice symmetry [107].…”