Taxonomic characterization and plant colonizing abilities of some bacteria related to Bacillus amyloliquefaciens and Bacillus subtilis

Abstract

The phylogenetic relationships of 17 Bacillus strains isolated from plants and soil were determined from partial sequences of genes encoding 16S rRNA, gyraseA (gyrA) and the cheA histidine kinase. Five strains were closely related to Bacillus subtilis subsp. subtilis, three strains were more closely related to B. subtilis subsp. spizizeni and two strains were identified as B. mojavensis. The remaining seven strains formed a cluster closely related to, but distinct from, Bacillus amyloliquefaciens. Some of these strains formed red-pigmented colonies. The abilities of selected strains to survive in the rhizosphere and to colonize plants were studied using oilseed rape (Brassica napus), barley (Hordeum vulgare) and thale cress (Arabidopsis thaliana) as model plants. It was shown by following the titre of bacteria in seedlings and by scanning electron microscopy that survival of Bacillus cells on the roots of seedlings during the first week after treatment of seeds with spore suspensions was crucial for colonization of the rhizosphere and for biocontrol activity. The group of strains related to B. amyloliquefaciens were generally better adapted to colonization of the rhizosphere of plants than other members of the B. subtilis group and could be considered a distinct ecotype of B. amyloliquefaciens. Bacteria in this taxon could be recognized on the basis of amplification of a PCR product with primers directed to the tetB(L) locus but no product with primers directed to the alpha-amylase gene of B.amyloliquefaciens sensu stricto.

Comparative analysis of the complete genome sequence of the plant growth–promoting bacterium Bacillus amyloliquefaciens FZB42

“…The resulting phylogenetic trees ( Supplementary Fig. 4 online) revealed that B. amyloliquefaciens FZB42 is rather close to strains recently introduced as endophytic or plant-associated ecomorphs of B. amyloliquefaciens 41 . Essentially all Bacillus strains that are currently commercialized for their plant growth-promoting and biocontrol activities belong to this ecotype.…”

Gene expression regulation in the plant growth promoting Bacillus atrophaeus UCMB-5137 stimulated by maize root exudates

“…Successful plant colonization by PGPR relied on multiple factors including but not limited to withstanding environmental stress (Reva et al, 2004), efficient chemotaxis (Yssel et al, 2011), effective communication within the bacterial communities and between bacteria and plants carried out by synthesized plant hormones and quorum sensing autoinducers (Lengeler & Postma 1999;Farag et al, 2013). All the factors are directly or indirectly related to effective sensing of environmental signals and proper regulation of gene expression.…”

Comparative structural bioinformatics analysis of Bacillus amyloliquefaciens chemotaxis proteins within Bacillus subtilis group

“…For instance, it was shown in experiments that in trans complementation of E. coli cells with knocked out chemotaxis proteins CheA and CheB with their counterparts from B. subtilis rescued the mutation (Garrity and Ordal 1995). It was shown in a previous study, that CheA is quite variable even on the level of subspecies of bacteria of B. subtilis group (Reva et al 2004). …”

“…They are commonly referred to as the B. subtilis group. Members of this group are free-living soil micro-organisms but several strains of B. amyloliquefaciens and B. subtilis are plant growth promoting rhizobacteria (PGPR) (Reva et al 2004). It has been shown that different strains of members of the B. subtilis group exhibit different specificity towards certain host plants (Reva et al 2004).…”

“…Members of this group are free-living soil micro-organisms but several strains of B. amyloliquefaciens and B. subtilis are plant growth promoting rhizobacteria (PGPR) (Reva et al 2004). It has been shown that different strains of members of the B. subtilis group exhibit different specificity towards certain host plants (Reva et al 2004). A recent paper argued that the chemotactic-competent bacteria present in the rhizosphere of wheat and cowpea are different from, and less diverse than, those in the bulk soil, indicating the development of specialized microbial communities (Buchan et al 2010).…”