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 proteins expressed provide a functional readout of the organism’s response to the environment. 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. In addition, 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 profile patterns for varied strains, we defined the proteomic profiles of four Group I 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 grown for five days. The four C. botulinum strains produced one of three neurotoxins (BoNT/A, /B, or /F), and their protein profiles were compared to that of a fifth non-toxigenic strain of C. sporogenes. These strains each had DNA sequences available to assist in accurate protein identification. Differing culture growth phase, bacterial strain, and growth medium resulted in reproducible protein profiles, which were used to calculate relative protein abundance ratios as an internally normalized metric of microbial growth in varying conditions. The resulting protein profiles provide functional information about how four Group I C. botulinum strains and a C. sporogenes strain respond to the culture environment during growth and explores the feasibility of using these proteins to characterize unknown samples.
Highlights
Genome analysis provides a significant amount of information about an organism’s biological potential, but complementary functional information, such as the proteome, provides a view of an organism’s reality; that is, its response to the environment in which it is growing
[8] the goals of this study were two-fold: 1) to use mass spectrometry complemented by genetic sequence data to characterize the protein profiles of four strains of Group I C. botulinum that express either botulinum neurotoxin (BoNT)/A, /B, or /F, and non-toxigenic C. sporogenes, and 2) to explore whether there are protein expression features in common among multiple Clostridium strains that can be attributed to biological processes and might prove useful in the characterization of unknown samples
The C. botulinum strains are closely related within the Group I species group, while the C. sporogenes strain is within a distinct clade that includes both BoNTproducing and non-neurotoxigenic members (Fig 1)
Summary
Genome analysis provides a significant amount of information about an organism’s biological potential, but complementary functional information, such as the proteome, provides a view of an organism’s reality; that is, its response to the environment in which it is growing. If it is known that an organism consistently expresses a set of proteins as part of a metabolic response to a growth medium, observation of those proteins in an unknown sample could facilitate deduction of characteristics of the growth environment from which it came. Most importantly, this would not be a “blind signature” of unrelated proteins that may be expressed, but rather a view of functional output with foundations in the underlying organism biology. C. botulinum will continue to be undefined on the protein level and will be limited in its understanding of other clostridial species.” [8] the goals of this study were two-fold: 1) to use mass spectrometry complemented by genetic sequence data to characterize the protein profiles of four strains of Group I C. botulinum that express either BoNT/A, /B, or /F, and non-toxigenic C. sporogenes, and 2) to explore whether there are protein expression features in common among multiple Clostridium strains that can be attributed to biological processes and might prove useful in the characterization of unknown samples
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