The role of fimV and the importance of its tandem repeat copy number in twitching motility, pigment production, and morphology in Legionella pneumophila.

Twitching motility, a flagella-independent type of translocation of bacteria over moist surfaces, requires an array of proteins, including FimV. To investigate the role of this protein in twitching motility in Legionella pneumophila, we have generated a knockout mutant of fimV and characterized its phenotypic effects. In addition to a major reduction in twitching motility, deletion of the fimV gene caused a number of other phenotypic effects including decreased protective pigment formation, and it also affected cell morphology. Since fimV contains a variable number of tandem repeats, which can vary according to the origin of a given strain, we have examined the importance of this variability found within the coding region of this gene. By complementing the knockout strain with constructs containing a different number of this tandem repeat, we have been able to also show that repeat copy number is important in the functioning of this gene.