Bacterial motility of freshwater isolates from the Kraus Wilderness Preserve

The low nutrient conditions of freshwater systems require bacteria to express mechanisms which aid in their survival and growth. Pseudomonas spp. and Burkholderia spp. can move to areas of desirable concentrations of nutrients via chemotactic responses and also produce siderophores - low-molecular weight compounds that chelate iron and make it available as a cellular nutrient. Because these bacteria live in oligotrophic environments, the goal was to investigate how the bacteria respond to various concentrations of nutrients via chemotaxis and the physical nature of the flagella used for this motility. Five water samples were collected from The Kraus Wilderness Preserve in Delaware, OH. Bacteria were isolated from these water samples using modified W-R media containing either sodium citrate, mannitol, L-alanine, or glucose as the sole carbon source. Once siderophore-producing, motile bacteria were isolated, oxidase tests, catalase tests, and Gram stains were done. These tests were used to separate potential Pseudomonas spp. and Burkholderia spp. from other isolates. Further identification of the five most motile isolates, as determined by microscopy, was performed using the Biolog GN2 MicroPlates super(TM) and BBL registered Enterotube super(TM) II systems. Growth curves were made of the two most motile isolates indicating a doubling time of 2727 minutes for isolate MBP2 and 1667 minutes for isolate SWC1 in W-R medium. Capillary tube chemotaxis assays were performed with the SWC1 isolates using sodium citrate, L-alanine, or a blue siderophore as possible chemoattractants. The blue siderophore elicited a chemotactic response as indicated by a relative response ratio of 2.236 for a 0.01 mM attractant concentration, while the remaining two substances were not chemoattractants. This blue siderophore will be identified using spectrometry while other chemoattractants are tested with isolate SWC1.