A protein complex supports the production of Spo0A‐P and plays additional roles for biofilms and the K‐state in Bacillus subtilis

• Published in: Molecular microbiology Vol. 101; no. 4; pp. 606 - 624
• Main Authors: Dubnau, Eugenie J., Carabetta, Valerie J., Tanner, Andrew W., Miras, Mathieu, Diethmaier, Christine, Dubnau, David
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-08-2016
• Subjects: Bacillus subtilis - genetics; Bacillus subtilis - metabolism; Bacillus subtilis - physiology; Bacterial Proteins - biosynthesis; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biofilms; Biofilms - growth & development; Mutation; Phosphorylation; Proteins; Spores, Bacterial - genetics; Spores, Bacterial - metabolism; Transcription Factors - biosynthesis; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription, Genetic
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.13411

Summary
Bacillus subtilis can enter three developmental pathways to form spores, biofilms or K‐state cells. The K‐state confers competence for transformation and antibiotic tolerance. Transition into each of these states requires a stable protein complex formed by YlbF, YmcA and YaaT. We have reported that this complex acts in sporulation by accelerating the phosphorylation of the response regulator Spo0A. Phosphorelay acceleration was also predicted to explain their involvement in biofilm formation and the K‐state. This view has been challenged in the case of biofilms, by the suggestion that the three proteins act in association with the mRNA degradation protein RNaseY (Rny) to destabilize the sinR transcript. Here, we reaffirm the roles of the three proteins in supporting the phosphorylation of Spo0A for all three developmental pathways and show that in their absence sinR mRNA is not stabilized. We demonstrate that the three proteins also play unknown Spo0A‐P‐independent roles in the expression of biofilm matrix and in the production of ComK, the master transcription factor for competence. Finally, we show that domesticated strains of B. subtilis carry a mutation in sigH, which influences the expression kinetics of the early spore gene spoIIG, thereby increasing the penetrance of the ylbF, ymcA and yaaT sporulation phenotypes.
In Bacillus subtilis, the proteins YlbF, YmcA and YaaT form a complex needed for the formation of biofilms, for sporulation and for genetic transformation. This paper strongly supports a role for these proteins in stimulating the phosphorylation of the key transcription factor, Spo0A. The present data contradict an alternative published model that proposed a role for the complex in destabilizing the mRNA for SinR, a repressor of biofilm formation.