Characterizing Cell Size-Colony Size Relationships in Heme Oxygenase Mutated Pseudomonas aeruginosa

Matthew Hudson*, Emel Sen-Kilic, Catherine Blackwood, Mariette Barbier, Ph.D.
Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV 26505

Presentation Category: Health Sciences (Poster presentation)

Student’s Major: Immunology and Medical Microbiology

Pseudomonas aeruginosa is among the leading Gram-negative organisms associated with nosocomial infections, responsible for a sizable amount of hospital-acquired pneumonia and urinary tract infections. The Centers for Disease Control and Prevention identified Gram-negative bacilli, such as P. aeruginosa, as a paramount threat to global health, citing the species’ high intrinsic rates of antibiotic-resistance. Currently, no vaccine exists for P. aeruginosa. As antimicrobial resistance continues to evolve, the need for a vaccine for this bacterium only increases. Our laboratory has an overarching goal of developing vaccines targeting bacterial acquisition of iron, a nutrient necessary for cellular and metabolic processes. We partnered with collaborators to examine the result of disrupted heme acquisition through the deletion of the heme oxygenase gene. The mutant strain did not infect as well as the parental strain and resulted in the formation of small colony variants during murine infection. The small colony variants did not grow as well as the parental strain, forming smaller colonies. We hypothesized that if the mutant strain formed smaller colonies and there was a relationship between cell size and colony size, then the mutant strain would yield smaller cells. Scanning electron microscopy allowed for the analysis of cells in both strains for comparison. Results indicate that the aforementioned hypothesis was not supported, as there was no relationship between cell size and colony size in heme oxygenase mutated P. aeruginosa. Further research can aid in identification of underlying causes for such results.

Funding: NIH

Program/mechanism supporting research/creative efforts: WVU's Research Apprenticeship Program (RAP) & accompanying HONR 297-level course