Taxonomy ofPseudomonasspp determines interactions withBacillus subtilis

Abstract

AbstractBacilli and pseudomonads are among the most well-studied microorganisms commonly found in soil, and frequently co-isolated. Despite this, no systematic approach has been employed to assess the pairwise compatibility of members from these genera. Here, we screened 720 fluorescent soil isolates for their effects onBacillus subtilispellicle formation in two types of media and found a predictor for interaction outcome inPseudomonastaxonomy. Interactions were context-dependent and both medium composition and culture conditions strongly influenced interactions. Negative interactions were associated withPseudomonas capeferrum, Pseudomonas entomophilaandPseudomonas protegens, and 2,4-diacetylphloroglucinol was confirmed as a strong (but not exclusive) inhibitor ofB. subtilis. Non-inhibiting strains were closely related toPseudomonas trivialisandPseudomonas lini, but in this case, cocultures with increasedB. subtilispellicle formation were spatially segregated. Our study is the first to propose an overall negative outcome from pairwise interactions betweenB. subtilisand fluorescent pseudomonads, hence cocultures comprising members from these groups are likely to require additional microorganisms for coexistence.