The effects of Bacillus subtilis on Caenorhabditis elegans fitness after heat stress

• Type of Material: Article
• Authors: Kim L. Hoang, Emory University; Nicole Marie Gerardo, Emory University; Levi T. Morran, Emory University
• Language: English
• Date: 2019-03-01
• Publisher: Wiley Open Access
• Publication Version: Final Published Version
• Copyright Statement: © 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1002/ece3.4983
• Title of Journal or Parent Work: Ecology and Evolution
• ISSN: 2045-7758
• Volume: 9
• Issue: 6
• Start Page: 3491
• End Page: 3499
• Grant/Funding Information: This material is based upon work supported by the NSF Graduate Research Fellowship Program under Grant No. DGE‐1444932 to KLH.; Nematode strain N2 Bristol and E. coli strains OP50 and OP50‐GFP were provided by the Caenorhabditis Genetics Center, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440).
• Keywords: abiotic; biotic; Bacillus subtilis; Caenorhabditis elegans; environmental stress; host-microbe association; offspring; host; reproduction; Escherichia coli; beneficial microbes; nematode; context-dependency; microbe; fitness
• Research Categories: Biology, General

Abstract

Microbes can provide their hosts with protection from biotic and abiotic factors. While many studies have examined how certain bacteria can increase host lifespan, fewer studies have examined how host reproduction can be altered. The nematode Caenorhabditis elegans has been a particularly useful model system to examine how bacteria affect the fitness of their hosts under different contexts. Here, we examine how the bacterium Bacillus subtilis, compared to the standard C. elegans lab diet, Escherichia coli, affects C. elegans survival and reproduction after experiencing a period of intense heat stress. We find that under standard conditions, nematodes reared on B. subtilis produce fewer offspring than when reared on E. coli.However, despite greater mortality rates on B. subtilis after heat shock, young adult nematodes produced more offspring after heat shock when fed B. subtilis compared to E. coli. Because offspring production is necessary for host population growth and evolution, the reproductive advantage conferred by B. subtilis supersedes the survival advantage of E. coli. Furthermore, we found that nematodes must be reared on B. subtilis (particularly at the early stages of development) and not merely be exposed to the bacterium during heat shock, to obtain the reproductive benefits provided by B. subtilis. Taken together, our findings lend insight into the importance of environmental context and interaction timing in shaping the protective benefits conferred by a microbe toward its host.