Horizontal transfer and evolution of wall teichoic acid gene cassettes in Bacillus subtilis

Abstract

Background: Wall teichoic acid (WTA) genes are essential for production of cell walls in gram-positive bacteria and necessary for survival and variability in the cassette has led to recent antibiotic resistance acquisition in pathogenic bacteria. Methods: Using a pan-genome approach, we examined the evolutionary history of WTA genes in Bacillus subtilis ssp. subtilis. Results: Our analysis reveals an interesting pattern of evolution from the type-strain WTA gene cassette possibly resulting from horizontal acquisition from organisms with similar gene sequences. The WTA cassettes have a high level of variation which may be due to one or more independent horizontal transfer events during the evolution of Bacillus subtilis ssp. subtilis. This swapping of entire WTA cassettes and smaller regions within the WTA cassettes is an unusual feature in the evolution of the Bacillus subtilis genome and highlights the importance of horizontal transfer of gene cassettes through homologous recombination within B. subtilis or other bacterial species. Conclusions: Reduced sequence conservation of these WTA cassettes may indicate a modified function like the previously documented WTA ribitol/glycerol variation. An improved understanding of high-frequency recombination of gene cassettes has ramifications for synthetic biology and the use of B. subtilis in industry.

Identification and Characterization of a New Regulator, TagR, for Environmental Stress Resistance Based on the DNA Methylome of Streptomyces roseosporus

“…In short, the WTA ABC transporter genes and their regulator gene tagR have diverse arrangements among Streptomyces spp. Recently, the same phenomenon for WTA gene cassettes was reported in B. subtilis ( 53 ). The diverse arrangement implies that the intensity of regulation of the WTA transporter may differ among strains, conferring different cell wall polyanionic matrices and determining the cationic binding capacity ( 54 ).…”

“…The diverse arrangement implies that the intensity of regulation of the WTA transporter may differ among strains, conferring different cell wall polyanionic matrices and determining the cationic binding capacity ( 54 ). By naturally rearranging their WTA cassettes, strains may be able to occupy diverse niches ( 53 ). Similarly, we may be able to exploit the TagR-WTA regulatory pathway to engineer strains with enhanced environmental stress resistance.…”

A pan-genome method to determine core regions of the Bacillus subtilis and Escherichia coli genomes

“…The variation of the WTA region in B. subtilis will be the focus of a future paper. 46 For the 34 protein coding genes from MiniBacillus 3 which were not in all 108 genomes (Supplementary Table 6), 10 were already discussed above as to why they were essential but not core. The seven essential genes previously shown to be protective essential genes are as expected not in the MiniBacillus data set.…”