Browsing by Author "Scott, Liam"

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Metabalomics Profiles of Ciproflaxacin Treated Staphylococcus aureus and Acinetobacter baumannii Biofilms
(Montana State University, 2017-04) Scott, Liam
Many bacterial organisms have the ability to form complex conglomerations of cells known as biofilms. It is important to understand this stage of bacterial life because it facilitates colonization and persistence in environments not suitable for planktonic cells. For example, biofilm structures grant an inherent resistance to antibiotic agents, a trait that is particularly concerning for infectious bacteria such as Staphylococcus aureus and Acinetobacter baumannii. With bacterial organisms such as these displaying powerful resistance to antibiotics, it is becoming ever more critical to understand biofilm structures, along with the inherent antibiotic resistance that they provide. To begin to understand these structures, many researchers have turned to analysis of the metabolomic profiles of bacterial species, and how those profiles differ between planktonic cells and biofilm conglomerations. In this project, it is proposed that the metabolomic profiles of S. aureus and A. baumannii will differ significantly between not only their free floating and biofilm states, but also in their antibiotic treated biofilm states. As such, I will work to combine an external metabolite analysis conducted using gas chromatography mass spectrometry (GCMS), with an internal metabolite analysis conducted using liquid chromatography mass spectrometry (LCMS), to create metabolomic profiles of each variant of these bacteria listed above. With this data, it will be possible to elucidate the biochemical pathways critical to S. aureus and A. baumannii biofilm antibiotic resistance. On a larger scale, this information will be critical in the pursuit of sensitizing S. aureus and A. baumannii to modern antibiotics.
Search for a Shared Genetic or Biochemical Basis for Biofilm Tolerance to Antibiotics across Bacterial Species
(American Society for Microbiology, 2022-04) Stewart, Philip S.; Williamson, Kerry S.; Boegli, Laura; Hamerly, Timothy; White, Ben; Scott, Liam; Hu, Xiao; Mumey, Brendan M.; Franklin, Michael J.; Bothner, Brian; Vital-Lopez, Francisco G.; Wallqvist, Anders; James, Garth A.
Is there a universal genetically programmed defense providing tolerance to antibiotics when bacteria grow as biofilms? A comparison between biofilms of three different bacterial species by transcriptomic and metabolomic approaches uncovered no evidence of one. Single-species biofilms of three bacterial species (Pseudomonas aeruginosa, Staphylococcus aureus, and Acinetobacter baumannii) were grown in vitro for 3 days and then challenged with respective antibiotics (ciprofloxacin, daptomycin, and tigecycline) for an additional 24 h. All three microorganisms displayed reduced susceptibility in biofilms compared to planktonic cultures. Global transcriptomic profiling of gene expression comparing biofilm to planktonic and antibiotic-treated biofilm to untreated biofilm was performed. Extracellular metabolites were measured to characterize the utilization of carbon sources between biofilms, treated biofilms, and planktonic cells. While all three bacteria exhibited a species-specific signature of stationary phase, no conserved gene, gene set, or common functional pathway could be identified that changed consistently across the three microorganisms. Across the three species, glucose consumption was increased in biofilms compared to planktonic cells, and alanine and aspartic acid utilization were decreased in biofilms compared to planktonic cells. The reasons for these changes were not readily apparent in the transcriptomes. No common shift in the utilization pattern of carbon sources was discerned when comparing untreated to antibiotic-exposed biofilms. Overall, our measurements do not support the existence of a common genetic or biochemical basis for biofilm tolerance against antibiotics. Rather, there are likely myriad genes, proteins, and metabolic pathways that influence the physiological state of individual microorganisms in biofilms and contribute to antibiotic tolerance.