AUTHOR=Oknin Hilla , Steinberg Doron , Shemesh Moshe 

TITLE=Magnesium ions mitigate biofilm formation of Bacillus species via downregulation of matrix genes expression

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00907

DOI=10.3389/fmicb.2015.00907

ISSN=1664-302X

ABSTRACT=<p>The objective of this study was to investigate the effect of Mg<sup>2+</sup> ions on biofilm formation by <italic>Bacillus</italic> species, which are considered as problematic microorganisms in the food industry. We found that magnesium ions are capable to inhibit significantly biofilm formation of <italic>Bacillus</italic> species at 50 mM concentration and higher. We further report that Mg<sup>2+</sup> ions don't inhibit bacterial growth at elevated concentrations; hence, the mode of action of Mg<sup>2+</sup> ions is apparently specific to inhibition of biofilm formation. Biofilm formation depends on the synthesis of extracellular matrix, whose production in <italic>Bacillus subtilis</italic> is specified by two major operons: the <italic>epsA-O</italic> and <italic>tapA</italic> operons. We analyzed the effect of Mg<sup>2+</sup> ions on matrix gene expression using transcriptional fusions of the promoters for <italic>eps</italic> and <italic>tapA</italic> to the gene encoding β galactosidase. The expression of the two matrix operons was reduced drastically in response to Mg<sup>2+</sup> ions suggesting about their inhibitory effect on expression of the matrix genes in <italic>B. subtilis</italic>. Since the matrix gene expression is tightly controlled by Spo0A dependent pathway, we conclude that Mg<sup>2+</sup> ions could affect the signal transduction for biofilm formation through this pathway.</p>