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2021 Abstracts

Paucilactobacillus wasatchsensis WCD04 biofilm formation and adherence to stainless steel

Presenter: Lizell Mejias, College of Science, Microbiology
Authors: Lizell A. Mejias, Michele C. Culumber, Craig J. Oberg
Faculty Advisors: Michele Culumber, College of Science, Microbiology
Institution: Weber State University

Paucilactobacillus wasatchsensis WCD04 is a gram-negative non-starter lactic acid bacterium (NSLAB). Its presence is characterized by gas production during the cheese aging process, which splits and cracks the cheese. This NSLAB is thought to be an environmental contaminant, but its reservoir is unknown. Plb. wasatchsensis does not survive heat exchange processing, its persistence in cheese manufacturing could be caused by post-pasteurization contamination and biofilm formation in cheese vats. We investigated different physiological conditions in which Plb. wasatchsensis reaches optimal growth for biofilm formation on stainless steel. Four days prior to the experiment, a WCD04 culture was grown on deMan Rogosa Sharpe broth with 1% ribose (MRS+R). A sterile polystyrene 24-well plate was divided into 6 columns that contained 2mL of MRS+R broth at different pH concentrations. Galactose was also added to the wells (0.5%,1% and 2%), this monosaccharide is known to be essential for the biosynthesis of exopolysaccharides in other bacillus species. Most of the wells were inoculated with 10 or 100 ul of culture, leaving an uninoculated control row. Round, flat, stainless-steel washers were clean disinfected with soap, ethanol, and autoclaved before adding one to each well. The plate was incubated at 30°C for a week. After the incubation period, the washers were removed with sterile forceps and rinsed with distilled water. Biofilm was removed by vortexing in 1ml of sterile saline for 1 min. The saline dilutions were plated in duplicate on MRS+R agar and incubated at 30°C anaerobically for five days. The data showed that bacterial attachment to the stainless steel occurred in the flat washers immersed in the pH 6 (100ul of WCD04, 1% and 2% galactose) and pH5 (10ul of WCD04, 0.5% and 1% galactose) wells. The uninoculated controls, pH 4 and 7 flat washer dilutions did not yield any growth.