The extracellular matrix protects Bacillus subtilis colonies from Pseudomonas invasion and modulates plant co-colonization

Abstract

Bacteria of the genera Pseudomonas and Bacillus can promote plant growth and protect plants from pathogens. However, the interactions between these plant-beneficial bacteria are understudied. Here, we explore the interaction between Bacillus subtilis 3610 and Pseudomonas chlororaphis PCL1606. We show that the extracellular matrix protects B. subtilis colonies from infiltration by P. chlororaphis . The absence of extracellular matrix results in increased fluidity and loss of structure of the B. subtilis colony. The P. chlororaphis type VI secretion system (T6SS) is activated upon contact with B. subtilis cells, and stimulates B. subtilis sporulation. Furthermore, we find that B. subtilis sporulation observed prior to direct contact with P. chlororaphis is mediated by histidine kinases KinA and KinB. Finally, we demonstrate the importance of the extracellular matrix and the T6SS in modulating the coexistence of the two species on melon plant leaves and seeds.

The manifold roles of microbial ribosomal peptide–based natural products in physiology and ecology

“…Moreover, the cannibalism has been shown to stimulate biofilm formation via the increased extracellular matrix production in B. subtilis, and both processes were triggered by the NRPS-derived lipopeptide surfactin (205). Interestingly, synthesis of an extracellular matrix and sporulation have been recently shown to be implicated in the interaction of B. subtilis and Pseudomonas chlororaphis that modulates plant co-colonization (206). This highlights that peptide-mediated cannibalism in sporulating bacteria is not only a mechanism of intraspecies interaction, but also should have a wider implication in interspecies interactions.…”

The Adaptive Morphology of Bacillus subtilis Biofilms: A Defense Mechanism against Bacterial Starvation

“…The formation of wrinkles in B. subtilis biofilms was reported to be a consequence of localized cell death [25], mechanical forces [26], and spatial gradients in metabolites [27]. Several beneficial features have been attributed to the wrinkled structure such as structural integrity, elasticity, liquid transport, hydrophobicity, and active protection from other species infiltration [28]. This paper addresses a possible role that the wrinkled architecture plays in B. subtilis colony-type biofilms grown in conditions of nutritive stress.…”

More than words: the chemistry behind the interactions in the plant holobiont

“…The presence of certain bacterial species can modulate the plant microbiome composition, and their effects on their host via antagonistic, competitive, and cooperative interactions can determine plant microbiota interactions under specific conditions (Rodriguez et al ., 2019). For this reason, recent efforts have focused on studying bacterial interactions, from simple interactions to those occurring in complex consortia, in an attempt to decipher how bacteria communicate and influence their local environment (Granato et al ., 2019; Molina‐Santiago et al ., 2019; Roder et al ., 2019; Roder et al ., 2020).…”