Novel surface layer protein genes in Bacillus sphaericus associated with unusual insertion elements.

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Surface layer (S-layer) proteins are crucial outer cell wall components in many bacteria.
• Understanding the genetic basis of S-layer protein diversity is key to bacterial evolution studies.

Purpose of the Study:

• To analyze and compare the S-layer protein genes in Bacillus sphaericus JG-A12 and B. sphaericus NCTC 9602.
• To investigate the evolutionary mechanisms behind S-layer gene diversity in these strains.

Main Methods:

• Comparative gene sequence analysis of S-layer proteins.
• Identification and characterization of mobile genetic elements associated with S-layer genes.
• Analysis of both chromosomal and plasmid-located S-layer gene copies.

Main Results:

• Identical N-terminal S-layer homologous (SLH) domains were found in both strains, with conserved central regions.
• Significant divergence was observed in the C-terminal regions of the S-layer proteins.
• A novel insertion element containing transposase and integrase genes, along with S-layer-like genes, was identified.
• Both strains harbor a silent, plasmid-located S-layer protein gene homologous to the chromosomal copies.

Conclusions:

• The S-layer protein gene structure in Bacillus sphaericus exhibits significant variability, particularly in C-terminal domains.
• Mobile genetic elements and horizontal gene transfer are strongly implicated in the evolution and diversification of S-layer protein genes.
• The presence of both chromosomal and silent plasmid-located genes suggests complex regulatory and evolutionary pathways.