In vitrocommunity synergy between bacterial soil isolates can be facilitated by pH stabilisation of the environment

Abstract

(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/347039 doi: bioRxiv preprint first posted online Jun. 14, 2018; 2 Abstract 24 Composition and development of naturally occurring microbial communities is defined by a 25 complex interplay between the community and the surrounding environment and by 26 interactions between community members. Intriguingly, these interactions can in some cases 27 cause community synergies where the community is able to outperform it single species 28 constituents. However, the underlying mechanisms driving community interactions are 29 often unknown and difficult to identify due to high community complexity. Here we show 30 how pH stabilisation of the environment through the metabolic activity of specific 31 community members acts as a positive inter-species interaction driving in vitro community 32 synergy in a model consortium of four co-isolated soil bacteria: Microbacterium oxydans, 33Xanthomonas retroflexus, Stenotrophomonas rhizophila and Paenibacillus amylolyticus. Using 34 micro-sensor pH measurements to show how individual species change the local pH micro-35 environment, and how co-cultivation leads to a stabilised pH regime over time. Specifically, 36 in vitro acid production from Paenibacillus amylolyticus and alkali production primarily from 37Xanthomonas retroflexus lead to an overall pH stabilisation of the local environment over 38 time, which in turn resulted in enhanced community growth. This specific type of inter-39 species interaction was found to be highly dependent on media type and media 40 concentration, however similar pH drift from the individual species could be observed 41 across media variants. 42 Importance 43We show that in vitro metabolic activity of individual members of a synthetic, co-isolated 44 model community presenting community synergistic growth arises through the inter-45

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