Three-Way Interactions in an Artificial Community of Bacterial Strains Directly Isolated From the Environment and Their Effect on the System Population Dynamics.

Óscar Adrián Gallardo-Navarro,Moisés Santillán

doi:10.3389/fmicb.2019.02555

Óscar Adrián Gallardo-Navarro, Moisés Santillán

Open Access

https://doi.org/10.3389/fmicb.2019.02555

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Abstract

This work is motivated by previous studies that have analyzed the population ecology of a collection of culturable thermoresistant bacteria, isolated from the Churince lagoon in Cuatro Cienegas, Mexico. In particular, it is aimed at testing a hypothesis from a modeling study, which states that antagonistic and sensitive bacteria co-exist thanks to resistant bacteria that protect sensitive ones by forming physical barriers. We selected three different bacterial strains from the referred collection: one antagonistic, one sensitive, and one resistant, and studied the population dynamics of mixed colonies. Our results show that, although the proposed protective mechanism does not work in this case, the resistant strain confers some kind of protection to sensitive bacteria. Further modeling and experimental results suggest that the presence of resistant bacteria indirectly improves the probability that patches of sensitive bacteria grow in a mixed colony. More precisely, our results suggest that by making antagonistic bacteria produce and secrete an antagonistic substance (with the concomitant metabolic cost and growth rate reduction), resistant bacteria increase the likelihood that sensitive bacteria locally outcompete antagonistic ones.

Highlights

Bacteria have existed on Earth for more than 3.5 billion years (Schopf, 1993), and in such time they have colonized nearly every surface on the planet
We have studied the population dynamics of Petri-dish mixed colonies, consisting of three different bacterial strains selected from the collection of culturable, thermoresistant bacteria originally isolated and studied by Pérez-Gutiérrez et al (2013)
We were able to prove with these strains that, the protective mechanism suggested by Zapién-Campos et al (2015) does not work in this case, the resistant strain confers some kind of protection to sensitive bacteria when the three of them are present in mixed colonies

Summary

Introduction

Bacteria have existed on Earth for more than 3.5 billion years (Schopf, 1993), and in such time they have colonized nearly every surface on the planet. Bacteria and other microorganisms form communities in which different species co-exist, share resources, and compete. Some important phenomena at planetary scale, like atmosphere oxygenation (Ohno, 1997) and biogeochemical cycles (Falkowski et al, 2008), are thought to be due to the action of bacterial communities. Despite the importance of bacterial communities, much of the research over the past one hundred years has focused on the growth and physiology of microbes grown in pure culture (Stubbendieck et al, 2016). Thanks in part to the availability of novel experimental

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