Suvanasuthi, Rooge<em>Silicibacter sp.</em> TM1040 is a member of the Roseobacter clade. Roseobacters play an important role in sulfur cycling in the ocean by degrading dimethylsulfoniopropionate (DMSP). Roseobacters are found in communities associated with most marine habits, especially with marine algae. Therefore, the ability to sense, move towards and maintain the interaction is an important physiological trait for the symbiosis between roseobacters and dinoflagellate. Previous work from our laboratory demonstrated that TM1040 is chemotaxis towards DMSP and DMSP catabolites, and motility of TM1040 is important for growth of <em>P. piscicida</em>. In contrast to enteric bacteria, little is known about the genes regulating motility in roseobacter species. This study, revealed similarities between the genes associated with motility in TM1040 and those from other α-proteobacteria species, but most importantly, it identified three new regulators that maybe involved in regulating the motility of TM1040.en-USThesisBiology, GeneticsBiology, MicrobiologyRoseobacterSilicibacter sp. TM1040motilityflagellar regulatorflagellar genesbiphasic life cycle