Rhamnolipid Independent Swarming of Pseudomonas aeruginosa

Swarming is a surface-associated motility where bacteria spread in groups, often as a precursor to biofilm formation. The bacterium Pseudomonas aeruginosa is known to swarm using its polar flagellum and a self-produced surfactant called rhamnolipid. This thesis details swarming in response to two types of environmental conditions: surface hardness and carbon source. It was found that swarm zone expansion and bacterial population are not linearly correlated during swarming and further that increased surface hardness significantly decreases rhamnolipid-dependent swarming. Secondly, it was found that a rhamnolipid-deficient P. aeruginosa strain swarmed upon the addition of the carbon source glutamate. This is unexpected, as no previous rhamnolipid-deficient swarming has been documented for P. aerguinosa. A mutagenesis approach was used to find gene(s) responsible for this rhamnolipid-independent swarm phenotype by probing for mutants that negate the glutamate swarming effect. Two thousand mutants were screened, twelve of which were found to not swarm with glutamate.