Shaping the microenvironment: evidence for the influence of a host galaxin on symbiont acquisition and maintenance in the squid‐vibrio symbiosis. (3rd June 2014)

• Record Type: Journal Article
• Authors: Heath‐Heckman, Elizabeth A. C.; Gillette, Amani A.; Augustin, René; Gillette, Miles X.; Goldman, William E.; McFall‐Ngai, Margaret J.
• Is Part Of: Environmental microbiology. Volume 16:Number 12(2014:Dec.)
• Page Start: 3669
• Page End: 3682
• Publication Date: 2014-06-03
• Subjects: Microbial ecology -- Periodicals; Environmental Microbiology -- Periodicals; 579.17
• DOI: 10.1111/1462-2920.12496
• Languages: English
• ISSNs: 1462-2912

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>Most bacterial species make transitions between habitats, such as switching from free living to symbiotic niches. We provide evidence that a galaxin protein, EsGal1, of the squid <italic>E</italic><italic>uprymna scolopes</italic> participates in both: (i) selection of the specific partner <italic>V</italic><italic>ibrio fischeri</italic> from the bacterioplankton during symbiosis onset and, (ii) modulation of <italic>V</italic><italic>. fischeri</italic> growth in symbiotic maintenance. We identified two galaxins in transcriptomic databases and showed by quantitative reverse‐transcriptase polymerase chain reaction that one (<italic>esgal1</italic>) was dominant in the light organ. Further, <italic>esgal1</italic> expression was upregulated by symbiosis, a response that was partially achieved with exposure to symbiont cell‐envelope molecules. Confocal immunocytochemistry of juvenile animals localized EsGal1 to the apical surfaces of light‐organ epithelia and surrounding mucus, the environment in which <italic>V</italic><italic>. fischeri</italic> cells aggregate before migration into the organ. Growth assays revealed that one repeat of EsGal1 arrested growth of Gram‐positive bacterial cells, which represent the cell type first 'winnowed' during initial selection of the symbiont. The EsGal1‐derived peptide also significantly decreased the growth rate of <italic>V</italic><italic>. fischeri</italic> in culture. Further, when animals were exposed to an anti‐EsGal1 antibody, symbiont population growth was significantly increased. These data provide a window into how hosts select symbionts from a rich environment and govern their growth in symbiosis.</p> </abstract>