Experimental bacterial adaptation to the zebrafish gut reveals a primary role for immigration

All animals live in intimate association with microorganisms that profoundly influence their health and development, yet the traits that allow microorganisms to establish and maintain host associations are not well understood. To date, most investigations aimed at identifying traits required for hos...

Full description

Saved in:

Bibliographic Details
Published in:	PLoS biology 2018-12, Vol.16 (12), p.e2006893
Main Authors:	Robinson, Catherine D, Klein, Helena S, Murphy, Kyleah D, Parthasarathy, Raghuveer, Guillemin, Karen, Bohannan, Brendan J M
Format:	Article
Language:	eng
Subjects:	Adaptation Adaptation, Biological - genetics Adaptation, Biological - physiology Aeromonas veronii - metabolism Aeromonas veronii - physiology Animals Aquatic environment Bacteria Biological Evolution Biology and Life Sciences Danio rerio Disease transmission Evolution Fitness Funding Gastrointestinal Microbiome - physiology Gastrointestinal Tract - microbiology Genomics Genotype & phenotype Genotypes Germfree Host Microbial Interactions - immunology Host Microbial Interactions - physiology Immigration Laboratories Larva - microbiology Materials science Medicine and Health Sciences Microbiota Microorganisms Molecular biology Mutagenesis Mutation Phylogeny Populations Reproductive fitness Research and Analysis Methods Selection, Genetic - genetics Selection, Genetic - physiology Vertebrates Zebrafish Zebrafish - microbiology
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	All animals live in intimate association with microorganisms that profoundly influence their health and development, yet the traits that allow microorganisms to establish and maintain host associations are not well understood. To date, most investigations aimed at identifying traits required for host association have focused on intrahost niches. Consequently, little is known about the relative contribution of extrahost factors such as environmental growth and survival and immigration into hosts from the external environment, as promoters of host association. To address this, we developed a tractable experimental evolution system that investigates both intra- and extrahost factors contributing to bacterial adaptation to the vertebrate gut. We passaged replicate lines of a zebrafish bacterial isolate, Aeromonas veronii, through populations of germ-free larval zebrafish (Danio rerio), each time using gut-associated Aeromonas populations to inoculate the aquatic environment of the next zebrafish population. We observed rapid increased adaptation to the host in all replicate lines. The initial adaptations present in early-evolved isolates did not increase intrahost fitness but rather enhanced both immigration from the environment and interhost transmission. Only in later-evolved isolates did we find evidence for intrahost-specific adaptations, as demonstrated by comparing their competitive fitness in the host genotype to which they evolved to that in a different genotype. Our results show how selection for bacterial transmission between hosts and their environment can shape bacterial-host association. This work illuminates the nature of selective forces present in host-microbe systems and reveals specific mechanisms of increased host association. Furthermore, our findings demonstrate that the entire host-microbe-environment system must be considered when identifying microbial traits that contribute to host adaptation.
ISSN:	1545-7885 1544-9173 1545-7885