title: Global discovery of colonization determinants in the squid symbiont Vibrio fischeri.
abstract: Animal epithelial tissue becomes reproducibly colonized by specific environmental bacteria. The bacteria (microbiota) perform critical functions for the host's tissue development, immune system development, and nutrition; yet the processes by which bacterial diversity in the environment is selected to assemble the correct communities in the host are unclear. To understand the molecular determinants of microbiota selection, we examined colonization of a simplified model in which the light organ of Euprymna scolopes squid is colonized exclusively by Vibrio fischeri bacteria. We applied high-throughput insertion sequencing to identify which bacterial genes are required during host colonization. A library of over 41,000 unique transposon insertions was analyzed before and after colonization of 1,500 squid hatchlings. Mutants that were reproducibly depleted following squid colonization represented 380 genes, including 37 that encode known colonization factors. Validation of select mutants in defined competitions against the wild-type strain identified nine mutants that exhibited a reproducible colonization defect. Some of the colonization factors identified included genes predicted to influence copper regulation and secretion. Other mutants exhibited defects in biofilm development, which is required for aggregation in host mucus and initiation of colonization. Biofilm formation in culture and in vivo was abolished in a strain lacking the cytoplasmic chaperone DnaJ, suggesting an important role for protein quality control during the elaboration of bacterial biofilm in the context of an intact host immune system. Overall these data suggest that cellular stress responses and biofilm regulation are critical processes underlying the reproducible colonization of animal hosts by specific microbial symbionts.
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611;
authors.forename: John F
authors.initials: JF
authors.lastname: Brooks
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611;
authors.forename: Mattias C
authors.initials: MC
authors.lastname: Gyllborg
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611;
authors.forename: David C
authors.initials: DC
authors.lastname: Cronin
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611;
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Quillin
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611;
authors.forename: Celeste A
authors.initials: CA
authors.lastname: Mallama
authors.affiliation: Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824; and.
authors.forename: Randi
authors.initials: R
authors.lastname: Foxall
authors.affiliation: Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824; and.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Whistler
authors.affiliation: Department of Microbial Pathogenesis and Microbial Sciences Institute, Yale University, New Haven, CT 06536.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Goodman
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611; m-mandel@northwestern.edu.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Mandel
mesh_terms: D048908:Aliivibrio fischeri / Q000235:genetics* / Q000502:physiology*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms; D004251:DNA Transposable Elements / Q000235:genetics; D049832:Decapodiformes / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D059014:High-Throughput Nucleotide Sequencing; D054884:Host-Pathogen Interactions; D064307:Microbiota / Q000235:genetics*; D016254:Mutagenesis, Insertional; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements
keywords: bacterial colonization; biofilm; chaperone; functional genomics; symbiosis