title: Magnesium ions mitigate biofilm formation of Bacillus species via downregulation of matrix genes expression.
abstract: The objective of this study was to investigate the effect of Mg(2+) ions on biofilm formation by Bacillus species, which are considered as problematic microorganisms in the food industry. We found that magnesium ions are capable to inhibit significantly biofilm formation of Bacillus species at 50 mM concentration and higher. We further report that Mg(2+) ions don't inhibit bacterial growth at elevated concentrations; hence, the mode of action of Mg(2+) ions is apparently specific to inhibition of biofilm formation. Biofilm formation depends on the synthesis of extracellular matrix, whose production in Bacillus subtilis is specified by two major operons: the epsA-O and tapA operons. We analyzed the effect of Mg(2+) ions on matrix gene expression using transcriptional fusions of the promoters for eps and tapA to the gene encoding β galactosidase. The expression of the two matrix operons was reduced drastically in response to Mg(2+) ions suggesting about their inhibitory effect on expression of the matrix genes in B. subtilis. Since the matrix gene expression is tightly controlled by Spo0A dependent pathway, we conclude that Mg(2+) ions could affect the signal transduction for biofilm formation through this pathway.
authors.affiliation: Department of Food Quality and Safety, Institute for Postharvest Technology and Food Sciences, Agricultural Research Organization, The Volcani Center Bet-Dagan, Israel ; Biofilm Research Laboratory, Faculty of Dental Medicine, Institute of Dental Sciences, Hebrew University-Hadassah Jerusalem, Israel.
authors.forename: Hilla
authors.initials: H
authors.lastname: Oknin
authors.affiliation: Biofilm Research Laboratory, Faculty of Dental Medicine, Institute of Dental Sciences, Hebrew University-Hadassah Jerusalem, Israel.
authors.forename: Doron
authors.initials: D
authors.lastname: Steinberg
authors.affiliation: Department of Food Quality and Safety, Institute for Postharvest Technology and Food Sciences, Agricultural Research Organization, The Volcani Center Bet-Dagan, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Shemesh
keywords: Bacillus species; biofilm formation; food industry; magnesium ions; microbial development