High prevalence of biofilm synergy among bacterial soil isolates in cocultures indicates bacterial interspecific cooperation

Abstract

Biofilms that form on roots, litter and soil particles typically contain multiple bacterial species. Currently, little is known about multispecies biofilm interactions and few studies have been based on environmental isolates. Here, the prevalence of synergistic effects in biofilm formation among seven different soil isolates, cocultured in combinations of four species, was investigated. We observed greater biofilm biomass production in 63% of the four-species culture combinations tested than in biofilm formed by single-species cultures, demonstrating a high prevalence of synergism in multispecies biofilm formation. One four-species consortium, composed of Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus, exhibited strong synergy in biofilm formation and was selected for further study. Of the four strains, X. retroflexus was the only one capable of forming abundant biofilm in isolation, under the in vitro conditions investigated. In accordance, strain-specific quantitative PCR revealed that X. retroflexus was predominant within the four-species consortium (497% of total biofilm cell number). Despite low relative abundance of all the remaining strains, all were indispensable for the strong synergistic effect to occur within the four-species biofilm. Moreover, absolute individual strain cell numbers were significantly enhanced when compared with those of single-species biofilms, indicating that all the individual strains benefit from inclusion in the multispecies community. Our results show a high prevalence of synergy in biofilm formation in multispecies consortia isolated from a natural bacterial habitat and suggest that interspecific cooperation occurs.

Distinct gene expression profile of Xanthomonas retroflexus engaged in synergistic multispecies biofilm formation

“…Further analysis of the metabolome and gene knockout experiments, especially targeting the amino acid biosynthesis pathways, will lead to further understanding of the molecular mechanisms behind the observed synergistic biofilm production (Ren et al, 2015).…”

“…Previously, we showed cooperative interactions between four soil isolates in a multispecies biofilm resulting in increased cell numbers and biofilm formation relative to single-species biofilms (Ren et al, 2015). A strong biofilm producer, Xanthomonas retroflexus, was combined with Stenotrophomonas rhizophila, Microbacterium oxydans and Paenibacillus amylolyticus and despite their incapability of single-species biofilm formation, the three other strains were indispensable for the strong synergy, which makes this consortium a powerful model for studying interactions in multispecies biofilms.…”

Microbial Surface Colonization and Biofilm Development in Marine Environments

“…This cooperation is essentially facilitated by the spatial juxtaposition of these two groups of bacteria and by the effective transfer of nitrite from AOB as a product of energy metabolism to NOB as a substrate for energy metabolism. In similar ways, coaggregation likely facilitates other metabolic cooperation processes via the transfer of other metabolites or energy in surface-associated microbial communities (632)(633)(634).…”

Next‐generation studies of microbial biofilm communities

“…For example, Burmolle et al . (2006) showed that a mixed species biofilm achieves significantly more biomass than the monospecies biofilms (Ren et al ., 2015), without the need to input more nutrients. Further, we and others have observed that such mixed communities have heightened tolerance to antimicrobials, chemical stress and predation (Burmolle et al ., 2006; Lee et al ., 2014; Kumar and Ting, 2015).…”

“…However, the results indicated that the communities within the anaerobic digestors were consistent at a species level, and thus the authors concluded that there must be other, strong selection forces at work within the reactors responsible for the community dynamic observed. Similarly, community composition and function have been described in terms of competition (Foster and Bell, 2012), cooperation (Ren et al ., 2015), resource partitioning and the role of interspecific and intraspecific variation in population‐ and community‐level resilience (Lee et al ., 2016). While microbiologists are increasingly embracing this approach, studies of molecular microbial ecology will greatly benefit not only from such an interdisciplinary uptake but ideally from the perspective of an experimental and theoretical platform where microbiologists and ecologists begin to unify macro‐ and micro‐ecology.…”