Novel whole-cell Reporter Assay for Stress-Based Classification of Antibacterial Compounds Produced by Locally Isolated Bacillus spp.

Reporter bacteria are beneficial for the rapid
and sensitive screening of cultures producing peptide
antibiotics, which can be an addition or alternative to the
established antibiotics. This study was carried out to validate
the usability of specific reporter strains for the target
mediated identification of antibiotics produced by native
Bacillus spp. isolated from different food sources. During
preliminary classification, cell wall stress causing Bacillus
isolates were screened by using reporter strain Bacillus
subtilis BSF2470. The isolates which induced cell wall
stress were further characterized for their specific mode of
action by using other B. subtilis reporter strains (TMB 488,
TMB 299 and TMB 279). The isolate B. licheniformis N12
was found to produce bacitracin confirmed by the response
to reporter strain B. subtilis TMB 279 and by putative
identification of bacitracin biosynthetic loci. The other
isolate B. subtilis EC1 also induced B. subtilis TMB 279,
but does not possess the bacitracin gene cluster indicating
that it can be a novel, bacitracin like antibiotic. The different
but related subsets of peptide antibiotics that bind the
pyrophosphate moiety of the lipid carrier of cell wall biosynthesis
can be identified using this whole cell based
reporter strains.