Examining The Tad Locus In Variovorax Paradoxus Eps And Its Tad Role In Motility

RM 216

Variovorax paradoxus is a gram-negative aerobic bacterium present in the human oral microbiome as well as the soil. This bacterium is known to play roles in biotransformation of xenobiotics and plant growth promotion. The genomes of two strains of Variovorax paradoxus, S110 and EPS, were recently published. Although the genome of strain EPS does not contain the flagellum operon that is annotated in S110, the microbe is demonstrably motile and flagella can be observed by staining. To explore this surprising finding further, we enriched for motility mutants from a Tn5 mutant library using a novel liquid culture settling strategy. 124 of the enriched motility mutants deviated significantly from wild-type in swarming motility, with 27 showing a complete loss of this activity. Of the 27, identification showed 11 different loci where insertion resulted in loss of motility. Among these loci several were repeatedly identified, including a putative fimbrial low-molecular-weight protein/fibril-associated protein (Flp/Fap) pilin component (Varpa_5148), and several genes annotated as parts of the tight adherence (Tad) locus (Varpa_5157-9). Based on work in other systems, these genes are likely involved in a single pilus biogenesis system, but the roles of these genes in swarming motility is unclear. Recent analysis of the V. paradoxus EPS transcriptome during logarithmic, stationary, and biofilm growth was combined with mutagenesis data to examine the possible role of antisense RNA regulation at this loci involved in motility. The Tn5 promoterless lacZ gene was used to help elucidate the role of the antisense expression in the regulation of these surface structures.