Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.

Bacterial mutualists are often acquired from the environment by eukaryotic hosts. However, both theory and empirical work suggest that this bacterial lifestyle is evolutionarily unstable. Bacterial evolution outside of the host is predicted to favor traits that promote an independent lifestyle in th...

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Autores principales:	Joel L Sachs, James E Russell, Amanda C Hollowell
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2011
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/b4e2a9f905cc4b97922a4023bed8d966
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spelling	oai:doaj.org-article:b4e2a9f905cc4b97922a4023bed8d9662021-11-18T07:35:13ZEvolutionary instability of symbiotic function in Bradyrhizobium japonicum.1932-620310.1371/journal.pone.0026370https://doaj.org/article/b4e2a9f905cc4b97922a4023bed8d9662011-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22073160/pdf/?tool=EBIhttps://doaj.org/toc/1932-6203Bacterial mutualists are often acquired from the environment by eukaryotic hosts. However, both theory and empirical work suggest that this bacterial lifestyle is evolutionarily unstable. Bacterial evolution outside of the host is predicted to favor traits that promote an independent lifestyle in the environment at a cost to symbiotic function. Consistent with these predictions, environmentally-acquired bacterial mutualists often lose symbiotic function over evolutionary time. Here, we investigate the evolutionary erosion of symbiotic traits in Bradyrhizobium japonicum, a nodulating root symbiont of legumes. Building on a previous published phylogeny we infer loss events of nodulation capability in a natural population of Bradyrhizobium, potentially driven by mutation or deletion of symbiosis loci. Subsequently, we experimentally evolved representative strains from the symbiont population under host-free in vitro conditions to examine potential drivers of these loss events. Among Bradyrhizobium genotypes that evolved significant increases in fitness in vitro, two exhibited reduced symbiotic quality, but no experimentally evolved strain lost nodulation capability or evolved any fixed changes at six sequenced loci. Our results are consistent with trade-offs between symbiotic quality and fitness in a host free environment. However, the drivers of loss-of-nodulation events in natural Bradyrhizobium populations remain unknown.Joel L SachsJames E RussellAmanda C HollowellPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 6, Iss 11, p e26370 (2011)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Joel L Sachs James E Russell Amanda C Hollowell Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.
description	Bacterial mutualists are often acquired from the environment by eukaryotic hosts. However, both theory and empirical work suggest that this bacterial lifestyle is evolutionarily unstable. Bacterial evolution outside of the host is predicted to favor traits that promote an independent lifestyle in the environment at a cost to symbiotic function. Consistent with these predictions, environmentally-acquired bacterial mutualists often lose symbiotic function over evolutionary time. Here, we investigate the evolutionary erosion of symbiotic traits in Bradyrhizobium japonicum, a nodulating root symbiont of legumes. Building on a previous published phylogeny we infer loss events of nodulation capability in a natural population of Bradyrhizobium, potentially driven by mutation or deletion of symbiosis loci. Subsequently, we experimentally evolved representative strains from the symbiont population under host-free in vitro conditions to examine potential drivers of these loss events. Among Bradyrhizobium genotypes that evolved significant increases in fitness in vitro, two exhibited reduced symbiotic quality, but no experimentally evolved strain lost nodulation capability or evolved any fixed changes at six sequenced loci. Our results are consistent with trade-offs between symbiotic quality and fitness in a host free environment. However, the drivers of loss-of-nodulation events in natural Bradyrhizobium populations remain unknown.
format	article
author	Joel L Sachs James E Russell Amanda C Hollowell
author_facet	Joel L Sachs James E Russell Amanda C Hollowell
author_sort	Joel L Sachs
title	Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.
title_short	Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.
title_full	Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.
title_fullStr	Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.
title_full_unstemmed	Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.
title_sort	evolutionary instability of symbiotic function in bradyrhizobium japonicum.
publisher	Public Library of Science (PLoS)
publishDate	2011
url	https://doaj.org/article/b4e2a9f905cc4b97922a4023bed8d966
work_keys_str_mv	AT joellsachs evolutionaryinstabilityofsymbioticfunctioninbradyrhizobiumjaponicum AT jameserussell evolutionaryinstabilityofsymbioticfunctioninbradyrhizobiumjaponicum AT amandachollowell evolutionaryinstabilityofsymbioticfunctioninbradyrhizobiumjaponicum
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Evolutionary instability of symbiotic function in Bradyrhizobium japonicum.

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