PNNL

Abstract

Microorganisms alter gene and protein expression in response to environmental conditions to adapt and survive. Whereas the genetic composition of a microbe represents an organism’s biological potential, the measurable protein expression provides a functional readout of the organism’s response to the environment. First, understanding protein expression patterns in response to specific environmental conditions furthers fundamental knowledge about a microbe, which can be especially useful for understudied organisms such as Clostridium botulinum examined herein. Secondly, protein expression patterns that reproducibly occur in certain growth conditions hold potential in fields such as microbial forensics, in which determination of conditions in which an unknown possible biothreat sample had been grown may be important. To investigate the identity and reproducibility of protein expression patterns for varied strains, we defined the proteomic profiles of four strains of Clostridium botulinum, a Category A biothreat agent and the organism responsible for the production of the botulinum neurotoxin (BoNT), in two different culture media. The four strains produced one of three neurotoxins (BoNT/A, /B, or /F), and their protein expression was compared to that of a fifth non-toxigenic strain of C. sporogenes. Differing culture growth phase, bacterial strain, and growth medium resulted in reproducible protein expression patterns, which were used to calculate relative protein abundance ratios as an internally normalized metric of microbial growth in varying conditions. As fundamental measures of an organism’s response to its environment, these metrics demonstrate the feasibility of using reproducible protein expression patterns to differentiate between cultivation conditions in the characterization of unknown samples.