A Two-component signal transduction thermosensor regulates swarming behavior in Serratia marcescens

• Main Authors: Wen-Ching Yih, 易文卿
• Other Authors: Hsin-Chin Lai
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/32385603053253290706

碩士 === 國立臺灣大學 === 醫事技術學研究所 === 89 === Swarming is a unique way of populational surface translocation. Serratia marcescens CH-1 swarming behavior is characterized by continuous populational surface migration on swarming agar at 30°C, but not at 37°C. The underlying mechanism of temperature-dependent swarming behavior is currently uncharacterized. A genetic locus is identified from a mini-Tn5 inserted mutant (named S. marcescens WC100) that, when mutated, results in a normal swarming behaviour phenotype at 37°C. The gene mutated (rssA, Regulation of Serratia Swarming A) is homologous to membrane sensor histidine kinases of the two-component family, suggesting that RssA may function as a sensor of environmental conditions required to regulate swarming migration. Architecture analysis shows that RssA has strong motif similarity to many other sensory proteins. Initiation of WC100 swarming is still cell density dependent, albeit cell elongation pattern during growth and the time of swarming initiation are affected. The mutant phenotype can be restored to the wild-type phenotype through complementation in trans by a plasmid-borne copy of rssA. Neither the swimming motility nor surfactant production is affected in WC100. However, WC100 biofilm capacity varies from its parent strain CH-1. Further study shows that production of total EPS and the ratio of unbound/bound form of EPS differ between WC100 and CH-1, suggesting that EPS production may be the dominant factor leading to the WC100 super-swarming phenotype. Upstream of RssA and transcribed in the same direction is another complete ORF (ORF2) found. ORF2 shows high amino acid sequence identity to the response regulators of two-component family. Upstream of ORF2 is an incomplete ORF3 found. ORF3 shows high homology to Bacillus subtilis FabG that is involved in the process of fatty acid synthesis. The possible mechanism of thermosensitive RssA in regulation of S. marcescens CH-1 swarming migration is discussed.