Macdonald, Julie (1987) Studies on motility in Rhodomicrobium vannielii. PhD thesis, University of Warwick.

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Abstract

The change from swarmer cell to non-motile reproductive cell was examined as a landmark event in differentiation of the purple non-sulphur bacterium, Rhodomicrobium vannielii, using synchronised swarmer cell populations.

It was found that shed flagella from Rm. vannielii consisted of 3 proteins: flagellin, Mr 34k, hook protein, Mr 36k and a polypeptide of Mr 37k, possibly rod protein. No methyl-accepting chemotaxis proteins were detected in Rm. vannielii.

Radioimmunoprecipitation was used to determine the period of flagellin synthesis during differentiation. Synthesis of flagellin was switched off in Rm. vannielii swarmer cells after 1-2 hours anaerobic incubation in the light. If swarmer cells were held anaerobically in the dark, flagellin synthesis continued for at least 6 hours. Thus, swarmer cells, which have a dispersal role in nature, detect whether environmental conditions are conducive to completion of the cell cycle, and regulate their gene expression accordingly. This contrasts with conclusions drawn from work with the non-photosynthetic aquatic bacterium, Caulobacter crescentus, whose cell cycle also includes a swarmer cell to non-motile reproductive cell transition.

In order to study control of flagellin expression further, cloning of the gene(s) was attempted. Heterologous Southern hybridisations between restricted Rm. vannielii chromosomal DNA and the cloned 29k flagellin gene from C. crescentus showed that 55-60% homology existed between the two. This was judged to be too weak a signal to allow cloning of Rm. vannielii flagellin genes by hybridisation. Antibodies raised against Rm. vannielii flagellin and hook protein did cross react with C. crescentrus flagellins and hook protein.

Screening a library of EcoRl digested Rm. vannielii chromosomal DNA in the vector λgt11 with anti-flagella antiserum indicated that Rm. vannielii flagellin and hook protein were not expressed in E. coli from DNA cut in such a way.

Eleven Tn5-induced motility mutants of Rm. vannielii were isolated (3 of which were chemotaxis deficient), and these should enable the cloning of genes for motility from this organism in the future.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QR Microbiology
Library of Congress Subject Headings (LCSH):	Bacteria -- Motility, Flagella (Microbiology), Cell differentiation, Gene expression
Official Date:	December 1987
Dates:	Date Event December 1987 Submitted
Institution:	University of Warwick
Theses Department:	Department of Biological Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Dow, Crawford S.
Sponsors:	Science and Engineering Research Council (Great Britain)
Format of File:	pdf
Extent:	xiii, 214 leaves : illustrations, charts, photographs
Language:	eng

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