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author:("Shi, wenchuan")
1.  A CheW Homologue Is Required for Myxococcus xanthus Fruiting Body Development, Social Gliding Motility, and Fibril Biogenesis 
Journal of Bacteriology  2002;184(20):5654-5660.
In bacteria with multiple sets of chemotaxis genes, the deletion of homologous genes or even different genes in the same operon can result in disparate phenotypes. Myxococcus xanthus is a bacterium with multiple sets of chemotaxis genes and/or homologues. It was shown previously that difA and difE, encoding homologues of the methyl-accepting chemoreceptor protein (MCP) and the CheA kinase, respectively, are required for M. xanthus social gliding (S) motility and development. Both difA and difE mutants were also defective in the biogenesis of the cell surface appendages known as extracellular matrix fibrils. In this study, we investigated the roles of the CheW homologue encoded by difC, a gene at the same locus as difA and difE. We showed that difC mutations resulted in defects in M. xanthus developmental aggregation, sporulation, and S motility. We demonstrated that difC is indispensable for wild-type cellular cohesion and fibril biogenesis but not for pilus production. We further illustrated the ectopic complementation of a difC in-frame deletion by a wild-type difC. The identical phenotypes of difA, difC, and difE mutants are consistent and supportive of the hypothesis that the Dif chemotaxis homologues constitute a chemotaxis-like signal transduction pathway that regulates M. xanthus fibril biogenesis and S motility.
doi:10.1128/JB.184.20.5654-5660.2002
PMCID: PMC139594  PMID: 12270823
2.  Construction and Characterization of a cheA Mutant of Treponema denticola 
Journal of Bacteriology  2002;184(11):3130-3134.
The Treponema denticola cheA gene, encoding the central kinase of the general chemotaxis pathway, was analyzed for its role in chemotaxis and tissue penetration. The cheA gene was interrupted by insertion of an ermF-ermAM gene cassette. Reverse transcription-PCR confirmed that the other downstream chemotaxis genes within the same operon (cheW, cheX, and cheY) were still expressed in the cheA mutant strain. Lack of cheA resulted in decreased swarming on soft-agar swarm plates and failure to respond chemotactically to a mixture of nutrients. Behavioral analyses using video microscopy revealed that the cheA mutant exhibited coordinated cell movement. The cellular reversal frequency, however, was severely reduced, indicating that CheA in T. denticola mainly controls cellular reversal and that active chemotaxis signaling input is not required for coordination of flagellar rotation at both cell poles.
doi:10.1128/JB.184.11.3130-3134.2002
PMCID: PMC135053  PMID: 12003957
3.  Mapping of Myxococcus xanthus Social Motility dsp Mutations to the dif Genes 
Journal of Bacteriology  2002;184(5):1462-1465.
Myxococcus xanthus dsp and dif mutants have similar phenotypes in that they are deficient in social motility and fruiting body development. We compared the two loci by genetic mapping, complementation with a cosmid clone, DNA sequencing, and gene disruption and found that 16 of the 18 dsp alleles map to the dif genes. Another dsp allele contains a mutation in the sglK gene. About 36.6 kb around the dsp-dif locus was sequenced and annotated, and 50% of the genes are novel.
doi:10.1128/JB.184.5.1462-1465.2002
PMCID: PMC134841  PMID: 11844780
4.  Type IV Pilus-Dependent Motility and Its Possible Role in Bacterial Pathogenesis  
Infection and Immunity  2002;70(1):1-4.
doi:10.1128/IAI.70.1.1-4.2002
PMCID: PMC127603  PMID: 11748156

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