Regulation of σ-Dependent Biofilm Formation in through Strain-Specific Signaling Induced by Diosgenin.

is a commensal skin bacterium and a causative agent of infectious diseases. Biofilm formation in is a mechanism that facilitates the emergence of resistant strains. This study proposes a mechanism for the regulation of biofilm formation in . through strain-specific physiological changes induced by the plant steroid diosgenin. A comparison of diosgenin-induced changes in the expression of regulatory genes associated with physiological changes revealed the intracellular regulatory mechanisms involved in biofilm formation. Diosgenin reduced biofilm formation in . ATCC 6538 and methicillin-resistant . (MRSA) CCARM 3090 by 39% and 61%, respectively. Conversely, it increased biofilm formation in . ATCC 29213 and MRSA CCARM 3820 by 186% and 582%, respectively. Cell surface hydrophobicity and extracellular protein and carbohydrate contents changed in a strain-specific manner in response to biofilm formation. An assessment of the changes in gene expression associated with biofilm formation revealed that diosgenin treatment decreased the expression of and and increased the expression of , , , and in . ATCC 6538 and MRSA CCARM 3090; however, contrasting gene expression changes were noted in . ATCC 29213 and MRSA CCARM 3820. These results suggest that a regulatory mechanism of biofilm formation is that activated expression sequentially increases the expression of , , and . This increased expression decreases the expression of , a surface-associated adhesion factor. An additional regulatory mechanism of biofilm formation is that activated expression decreases the expression of an unknown regulator that increases the expression of . This in turn decreases the expression of , which decreases the synthesis of polysaccharide intercellular adhesins and ultimately inhibits biofilm formation. By assessing strain-specific contrasting regulatory signals induced by diosgenin in . without gene mutation, this study elucidated the signal transduction mechanisms that regulate biofilm formation based on physiological and gene expression changes.