Bacillus cereus & Bacillus pumilus Harvested from a Copper Roof Inhibit the Growth of Other Microorganisms

Abstract

Bacteria growing under the effects of unique selective pressures have distinct adaptations allowing them to survive. Copper surfaces present challenges for bacterial survival because ions dissolve from the surfaces and disrupt cell membranes, thus inhibiting bacterial growth. In this study, the copper roof of Simons Hall in Collegeville, Minnesota was sampled for bacterial species during November 2018. Bacteria were isolated and grown in culture, and zones of inhibition were identified surrounding three of the bacterial colonies. Polymerase chain reaction (PCR) was used to identify two of the bacteria samples as Bacillus cereus and a third sample as Bacillus pumilus. Bacilli are large, rod-shaped, gram-positive bacteria commonly found in diverse environments. They are endospore-forming aerobes or facultative anaerobes. Initial experiments indicated that all three Bacillus strains had the ability to inhibit the growth of three environmental microorganisms. Results from growth curve experiments depicted inhibitory effects on environmental microorganisms at all stages of the growth curve, which is contrary to the prediction that the inhibitory behavior would appear at one specific period of the growth curve. Additional experiments involved plating isolates of Bacillus cereus and Bacillus pumilus with laboratory samples of Pseudomonas aeruginosa, Streptococcus pneumoniae, and Listeria monocytogenes to further understand the effectiveness of B. cereus and B. pumilus at inhibiting the growth of other microorganisms. These findings support previous studies and suggest that Bacillus are capable of inhibiting or killing other organisms. Further research will be conducted to illuminate the inhibitory mechanisms and identify potential therapeutic possibilities. KEYWORDS: Bacteria; Copper; Resistance; Growth Curve; Inhibition; Bacillus; Bacteriocin; Antimicrobial Peptides