Evaluation of an ATP Assay to Quantify Bacterial Attachment to Wetted Surfaces in Variable Gravity Conditions

摘要

The goal of this experimentation was to develop an assay to quantify the biomass of attached cells and biofilm formed on wetted surfaces in variable gravity environments. Liquid cultures of Pseudomonas aeruginosa were exposed to 30-35 brief cycles of hypergravity (< 2 g) followed by free fall (i.e., reduced gravity) equivalent to either lunar g (i.e., 0.17 normal Earth gravity) or micro g (i.e., < 0.001 normal Earth gravity) in an aircraft flying a series of parabolas. Over the course of two days of parabolic flight testing, 504 polymer or metal coupons were exposed to a stationary-phase population of P. aeruginosa strain ERC1 at a concentration of 1 × 10~5 cells/milliliter. After the final parabola on each flight test day, half of the material coupon samples were treated with either 400 ug L-l ionic silver fluoride (microgravity-exposed cultures) or 1% formalin (lunar gravity-exposed cultures). The remaining sample coupons from each flight test day were not treated with a fixative. All samples were returned to the laboratory for analysis within 2 hours of landing, and all biochemical assays were completed within 8 hours of exposure to variable gravity. The intracellular ATP luminescent assay accurately reflected cell physiology compared to both cultivation-based and direct-count microscopy analyses. Cells exposed to variable gravity had more than twice as much intracellular ATP as control cells exposed only to normal terrestrial gravity.