Expression of degQ gene and its effect on lipopeptide production as well as formation of secretory proteases in Bacillus subtilis strains

<em>Bacillus subtilis</em> is described as a promising production strain for lipopeptides. In case of <em>B. subtilis</em> strains JABs24 and DSM10^T, surfactin and plipastatin are produced. Lipopeptide formation is controlled, among others, by the DegU response regulator. The activating phospho-transfer by the DegS sensor kinase is stimulated by the pleiotropic regulator DegQ, resulting in enhanced DegU activation. In <em>B. subtilis</em> 168, a point mutation in the <em>degQ</em> promoter region leads to a reduction in gene expression. Corresponding reporter strains showed a 14-fold reduced expression. This effect on <em>degQ</em> expression and the associated impact on lipopeptide formation was examined for <em>B. subtilis</em> JABs24, a lipopeptide-producing derivative of strain 168, and <em>B. subtilis</em> wild-type strain DSM10^T, which has a native <em>degQ</em> expression. Based on stimulatory effects of the DegU regulator on secretory protease formation, the impact of <em>degQ</em> expression on extracellular protease activity was additionally investigated. To follow the impact of <em>degQ</em>, a deletion mutant was constructed for DSM10^T, while a natively expressed <em>degQ</em> version was integrated into strain JABs24. This allowed strain-specific quantification of the stimulatory effect of <em>degQ</em> expression on plipastatin and the negative effect on surfactin production in strains JABs24 and DSM10^T. While an unaffected <em>degQ</em> expression reduced surfactin production in JABs24 about 25%, a 6-fold increase in plipastatin was observed. In contrast, <em>degQ</em> deletion in DSM10^T increased surfactin titer by 3-fold but decreased plipastatin production by 5-fold. In addition, although significant differences in extracellular protease activity were detected, no decrease in plipastatin and surfactin produced during cultivation was observed.