The bacterial endosymbionts of the hydrothermal vent tubeworm Riftia pachyptila play a key role in providing their host with fixed carbon. Results of prior research suggest that the symbionts are selected from an environmental bacterial population, although a free-living form has been neither cultured from nor identified in the hydrothermal vent environment. To begin to assess the free-living potential of the symbiont, we cloned and characterized a flagellin gene from a symbiont fosmid library. The symbiont fliC gene has a high degree of homology with other bacterial flagellin genes in the amino- and carboxy-terminal regions, while the central region was found to be nonconserved. A sequence that was homologous to that of a consensus σ28 RNA polymerase recognition site lay upstream of the proposed translational start site. The symbiont protein was expressed in Escherichia coli, and flagella were observed by electron microscopy. A 30,000-M(r) protein subunit was identified in whole-cell extracts by Western blot analysis. These results provide the first direct evidence of a motile free- living stage of a chemoautotrophic symbiont and support the hypothesis that the symbiont of R. pachyptila is acquired with each new host generation.
CITATION STYLE
Millikan, D. S., Felbeck, H., & Stein, J. L. (1999). Identification and characterization of a flagellin gene from the endosymbiont of the hydrothermal vent tubeworm Riftia pachyptila. Applied and Environmental Microbiology, 65(7), 3129–3133. https://doi.org/10.1128/aem.65.7.3129-3133.1999
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