As a soil dwelling bacterium Bacillus subtilis is exposed to constant, often life-threatening changes in conditions. To manage these challenges, the bacterium employs alternative σ-factors, activating a response that enables cellular adaptation to environmental stressors. Membrane-associated proteins play a crucial role in perceiving these environmental changes, with one notable complex being PspA-YdjGHI, housing the SPFH (Stomatin/Prohibitin/Flotillin/HflK-C) protein, YdjI (1). Members of this widely conserved family are associated with regulation of membrane fluidity (2,3) and are known for their impact on a variety of membrane bound processes, including developmental processes in B. subtilis (4,5). Here, we show that YdjI is required for efficient motility and development of social communities. Deleting ydjI impairs biofilm formation and prevents the formation of the BlsA hydrophobic biofilm coat. We further show that the deletion of ydjI leads to an upregulation of the σ^B answer and a downregulation of the ytrABCDEF operon. This operon encodes for an ABC transporter of unknown function, its own regulator, and the FtsX-like membrane associated protein YtrF (6). Deletion of ytrF phenocopies the biofilm defects observed for the ydjI deletion. Interestingly RNA Seq of biofilms of ydjI and ytrF mutants revealed an induction of gene clusters associated with σ^B activation. Together, our data strongly suggest that the biofilm related phenotypes are caused by a defect during the initiation of differentiation that likely originates from the general stress response due to energy starvation.

(1) Savietto Scholz, A., et al. (2021) Front. Microbiol. 12: 754924
(2) Bach, J.N. et al. (2013) Mol. Micro. 88:1205-1217
(3) Zielińska, A., et al. (2020) Elife 9:e57179
(4) Yepes A, et al. (2012) Mol Microbiol. 86(2):457-471
(5) Dempwolff F, et al. (2012) J Bacteriol. 194(17):4652-61
(6) Benda M, et al. (2021) Front Microbiol. 12:587035