Genetic determinants of swimming motility in the squid light-organ symbiont Vibrio fischeri
Version of Record online: 12 JUN 2013
© 2013 The Authors. Microbiology Open published by John Wiley & Sons Ltd.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Volume 2, Issue 4, pages 576–594, August 2013
How to Cite
MicrobiologyOpen 2013; 2(4): 576–594
- Issue online: 12 AUG 2013
- Version of Record online: 12 JUN 2013
- Manuscript Accepted: 6 MAY 2013
- Manuscript Revised: 19 APR 2013
- Manuscript Received: 9 FEB 2013
- National Institutes of Health. Grant Number: RR12294
- National Science Foundation. Grant Number: IOS-0817232
- National Institutes of Health Molecular Biosciences. Grant Number: T32 GM07215
- National Institutes of Health Microbes in Health and Disease. Grant Number: T32 AI55397
- University of Wisconsin-Madison
- NRSA. Grant Number: IOS-0843633
- Euprymna scolopes ;
- Flagellar motility;
Bacterial flagellar motility is a complex cellular behavior required for the colonization of the light-emitting organ of the Hawaiian bobtail squid, Euprymna scolopes, by the beneficial bioluminescent symbiont Vibrio fischeri. We characterized the basis of this behavior by performing (i) a forward genetic screen to identify mutants defective in soft-agar motility, as well as (ii) a transcriptional analysis to determine the genes that are expressed downstream of the flagellar master regulator FlrA. Mutants with severe defects in soft-agar motility were identified due to insertions in genes with putative roles in flagellar motility and in genes that were unexpected, including those predicted to encode hypothetical proteins and cell division–related proteins. Analysis of mutants for their ability to enter into a productive symbiosis indicated that flagellar motility mutants are deficient, while chemotaxis mutants are able to colonize a subset of juvenile squid to light-producing levels. Thirty-three genes required for normal motility in soft agar were also downregulated in the absence of FlrA, suggesting they belong to the flagellar regulon of V. fischeri. Mutagenesis of putative paralogs of the flagellar motility genes motA, motB, and fliL revealed that motA1, motB1, and both fliL1 and fliL2, but not motA2 and motB2, likely contribute to soft-agar motility. Using these complementary approaches, we have characterized the genetic basis of flagellar motility in V. fischeri and furthered our understanding of the roles of flagellar motility and chemotaxis in colonization of the juvenile squid, including identifying 11 novel mutants unable to enter into a productive light-organ symbiosis.