Identification and characterization of a flagellin gene from the endosymbiont of the hydrothermal vent tubeworm Riftia pachyptila.
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 sigma28 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-Mr 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.
Millikan
D S
DS
Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0202, USA.
Felbeck
H
H
Stein
J L
JL
D000818:Animals; D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D018407:Bacterial Physiological Phenomena; D015153:Blotting, Western; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005408:Flagellin / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D005798:Genes, Bacterial; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009068:Movement; D011077:Polychaeta / Q000382:microbiology*; D013559:Symbiosis
D005408:Flagellin