Biology subjects

Schlimpert, S.

Publications and source records attributed to Schlimpert, S..

4 recordsLinked to original sources

bioRxiv2022

Cytoplasmic contractile injection systems mediate cell death in Streptomyces

Contractile injection systems (CISs) are bacteriophage tail-like structures that mediate bacterial cell-cell interactions. While CISs are highly abundant across diverse bacterial phyla, representative gene clusters in Gram-positive organisms remain poorly studied. Here we characterize a CIS in the Gram-positive multicellular model organism Streptomyces coelicolor and show, that in contrast to most other CISs, S. coelicolor CIS (CISSc) mediate cell death in response to stress and impact cellular development. CISSc are expressed in the cytoplasm of vegetative hyphae and not released into the medium. Our cryo-electron microscopy structure enabled the engineering of non-contractile and fluorescently tagged CISSc assemblies. Cryo-electron tomography showed that CISSc contraction is linked to reduced cellular integrity. Fluorescence light microscopy furthermore revealed that CISSc contraction mediates cell death upon encountering different types of stress. Finally, the absence of functional CISSc had an impact on hyphal differentiation and secondary metabolite production. Our results provide new functional insights into CISs in Gram-positive organisms and a framework for studying novel intracellular roles, including regulated cell death and life cycle progression in multicellular bacteria.

microbiology↗

bioRxiv2022

Genome-wide identification of the LexA-mediated DNA damage response in Streptomyces venezuelae

DNA damage triggers a widely conserved stress response in bacteria called the SOS response that involves two key regulators, the activator RecA and the transcriptional repressor LexA. Despite the wide conservation of the SOS response, the number of genes controlled by LexA varies considerably between different organisms. The filamentous soil-dwelling bacteria of the genus Streptomyces contain LexA and RecA homologs but their roles in Streptomyces have not been systematically studied. Here, we demonstrate that RecA and LexA are required for the survival of Streptomyces venezuelae during DNA damaging conditions and for normal development during unperturbed growth. Monitoring the activity of a fluorescent recA promoter fusion and LexA protein levels revealed that the activation of the SOS response is delayed in S. venezuelae. By combining global transcriptional profiling and ChIP-seq analysis, we determined the LexA regulon and defined the core set of DNA damage repair genes that are expressed in response to treatment with the DNA alkylating agent mitomycin C. Our results show that DNA damage-induced degradation of LexA results in the differential regulation of LexA target genes. Using Surface Plasmon Resonance, we further confirm the LexA DNA binding motif (SOS box) and demonstrate that LexA displays tight but distinct binding affinities to its target promoters, indicating a graded response to DNA damage. IMPORTANCEThe transcriptional regulator LexA functions as a repressor of the bacterial SOS response, which is induced during DNA damaging conditions. This results in the expression of genes important for survival and adaptation. Here, we report the regulatory network controlled by LexA in the filamentous antibiotic producing Streptomyces bacteria and establish the existence of the SOS response in Streptomyces. Collectively, our work reveals significant insights into the DNA damage response in Streptomyces that will promote further studies to understand how these important bacteria adapt to their environment.

microbiology↗

bioRxiv2021

Multicellular growth and sporulation in filamentous actinobacteria require the conserved cell division protein SepX

Filamentous actinobacteria such as Streptomyces undergo two distinct modes of cell division, leading to partitioning of growing hyphae into multicellular compartments via cross-walls, and to septation and release of unicellular spores. Specific determinants for cross-wall formation and the importance of hyphal compartmentalization for Streptomyces development are largely unknown. Here we show that SepX, an actinobacterial-specific protein, is crucial for both cell division modes in Streptomyces venezuelae. Importantly, we find that sepX-deficient mutants grow without cross-walls and that this substantially impairs the fitness of colonies and the coordinated progression through the developmental life cycle. Protein interaction studies and live-cell imaging suggest that SepX contributes to the stabilization of the divisome, a mechanism that also requires the dynamin-like protein DynB. Thus, our work identifies an important determinant for cell division in Streptomyces that is required for cellular development and sporulation.

microbiology↗

bioRxiv2020

A conserved cell division protein directly regulates FtsZ dynamics in filamentous and unicellular actinobacteria

Bacterial cell division is driven by the polymerization of the GTPase FtsZ into a contractile structure, the so-called Z-ring. This essential process involves proteins that modulate FtsZ dynamics and hence the overall Z-ring architecture. Actinobacteria, like Streptomyces and Mycobacterium lack known key FtsZ-regulators. Here we report the identification of SepH, a conserved actinobacterial protein that directly regulates FtsZ dynamics. We show that SepH is crucially involved in cell division in Streptomyces and that it binds FtsZ via a conserved helix-turn-helix motif, stimulating the assembly of FtsZ protofilaments. Comparative in vitro studies using the SepH homolog from Mycobacterium further reveal that SepH can also bundle FtsZ protofilaments, indicating an additional Z-ring stabilizing function in vivo. We propose that SepH plays a crucial role at the onset of cytokinesis in actinobacteria by promoting the rapid assembly of FtsZ filaments into division-competent Z-rings that can go on to mediate septum synthesis.

microbiology↗