Biology subjects

Derkacz, M.

Publications and source records attributed to Derkacz, M..

2 recordsLinked to original sources

bioRxiv2024

Roles of PknB and CslA in cell wall morphogenesis of Streptomyces

The bacterial cell wall is essential for maintaining cellular integrity and defining the mode of growth, with different species adopting distinct strategies for cell wall synthesis and remodelling. Streptomyces are filamentous bacteria predominantly found in soil and renowned for producing specialised metabolites, including antibiotics. They grow through tip extension and branching hyphal filaments, forming a multicellular mycelium. New branches are established by forming a new growth zone on the lateral cell wall. Proteins involved in this process are organised into complexes called polarisomes, with DivIVA being the most well-characterised component. To investigate the tip growth requirements in Streptomyces albus we developed a genetic screen utilising toxic DivIVA overproduction and searched for suppressors of its lethality, reasoning that such suppressors would likely encode components functionally linked to DivIVA or the tip growth machinery. Among the identified genes was pknB, encoding a serine/threonine protein kinase implicated in the regulation of cell growth and morphogenesis. We confirmed that deletion of pknB restored the growth phenotype of S. albus following DivIVA overproduction. The phosphoproteome analysis revealed that the absence of PknB alters the phosphorylation state of CslA, a cellulose synthase-like protein. We demonstrate that a phosphoablative mutant of CslA impairs {beta}-glucan synthesis and causes hypersensitivity to lysozyme. Overproduction of CslA restored colony growth defects arising from DivIVA-induced hyperbranching, without however suppressing the hyperbranching phenotype. These findings collectively identify PknB-dependent phosphorylation of CslA as a central regulatory point in Streptomyces cell envelope construction, revealing how modulation of {beta}-glucan synthesis can mitigate the cellular consequences of DivIVA dysregulation.

microbiology↗

bioRxiv2024

The gamma-butyrolactone receptors ScbR and AtrA form a quorum sensing switch between coelimycin and actinorhodin synthesis in Streptomyces coelicolor A3(2)

BackgroundQuorum sensing enables gene expression regulation in response to changes in cell population density and controls diverse processes, such as biofilm formation, virulence and antibiotic production, in bacteria. In one of the largest, soil-dominant phylum Actinobacteria, cell-to-cell communication occurs through the small, membrane-diffusible signalling molecules gamma-butyrolactones (GBLs). Their actions are exerted through receptor proteins that also act as response regulators in a one-component system manner. With only a few GBL systems characterized, most of them come from the large, antibiotic-producer genus Streptomyces. In the model organism Streptomyces coelicolor A3(2), two GBL receptors, ScbR and SlbR, which are both antibiotic production repressors, have been reported so far. ResultsIn this work, we identified a new GBL receptor protein, the conserved and pleiotropic regulator AtrA, which has an activating mode of action. Moreover, we elucidated the precise mechanism by which it controls the production of the antibiotic actinorhodin through the actinorhodin biosynthetic gene cluster activator ActII-orf4. GBL binding to AtrA prevents its binding to the promoter of the actII-orf4 gene, thereby disabling its transcription, while at the same time, GBL binding to ScbR causes coelimycin antibiotic synthesis derepression. ConclusionsThe opposite modes of action of ScbR (repressor) and AtrA (activator) have opposite effects upon GBL binding, activating coelimycin and blocking actinorhodin production at the same time. This phenomenon constitutes an elegant regulatory mechanism that ensures that coelimycin and actinorhodin production are mutually exclusive. These findings also suggest that quorum sensing must be taken into account when designing efficient antibiotic production processes and can be manipulated to ensure both better yield and specificity.

molecular biology↗