Biology subjects

Karinou, E.

Publications and source records attributed to Karinou, E..

4 recordsLinked to original sources

bioRxiv2023

A one-track model for spatiotemporal coordination of Bacillus subtilis septal cell wall synthesis

Bacterial cell division requires synthesis of a septal peptidoglycan (sPG) wall across the middle of the cell. This is accomplished by the divisome synthesis complex in coordination with numerous other division proteins--such as the essential tubulin homolog FtsZ--but the molecular mechanism of its spatiotemporal regulation remains unclear. Here, we investigate the dynamics of sPG synthesis in the model Gram-positive bacterium Bacillus subtilis using live-cell single-molecule imaging of the divisome transpeptidase PBP2B. In contrast to previous models for division, we show that there is a single population of processively-moving PBP2B molecules whose motion is driven by peptidoglycan synthesis and is not associated with FtsZ treadmilling. However, although the motions of PBP2B and FtsZ are asynchronous, we demonstrate that processive PBP2B motion is partially dependent on FtsZ treadmilling. Additionally, we provide evidence that the divisome synthesis complex is multimeric. Our results support a new model for division in B. subtilis where a multimeric synthesis complex follows a single track dependent on sPG synthesis whose activity and dynamics are asynchronous with FtsZ treadmilling.

microbiology↗

bioRxiv2020

FtsZ treadmilling is essential for Z-ring condensation and septal constriction initiation in bacterial cell division

Despite the central role of division in bacterial physiology, how division proteins work together as a nanoscale machine to divide the cell remains poorly understood. Cell division by cell wall synthesis proteins is guided by the cytoskeleton protein FtsZ, which assembles at mid-cell as a dense Z-ring formed of treadmilling filaments1,2. However, although FtsZ treadmilling is essential for cell division, the function of FtsZ treadmilling remains unclear2-5. Here, we systematically resolve the function of FtsZ treadmilling across each stage of division in the Gram-positive model organism Bacillus subtilis using a novel combination of nanofabrication, advanced microscopy, and microfluidics to measure the division-protein dynamics in live cells with ultrahigh sensitivity. We find that FtsZ treadmilling has two essential functions: mediating condensation of diffuse FtsZ filaments into a dense Z-ring, and initiating constriction by guiding septal cell wall synthesis. After constriction initiation, FtsZ treadmilling has a dispensable function in accelerating septal constriction rate. Our results show that FtsZ treadmilling is critical for assembling and initiating the bacterial cell division machine.

microbiology↗

bioRxiv2020

ZeroCostDL4Mic: an open platform to simplify access and use of Deep-Learning in Microscopy

The resources and expertise needed to use Deep Learning (DL) in bioimaging remain significant barriers for most laboratories. We present https://github.com/HenriquesLab/ZeroCostDL4Mic/wiki, a platform simplifying access to DL by exploiting the free, cloud-based computational resources of Google Colab. https://github.com/HenriquesLab/ZeroCostDL4Mic/wiki allows researchers to train, evaluate, and apply key DL networks to perform tasks including segmentation, detection, denoising, restoration, resolution enhancement and image-to-image translation. We demonstrate the application of the platform to study multiple biological processes.

bioinformatics↗

bioRxiv2018

Inactivation of the monofunctional peptidoglycan glycosyltransferase SgtB allows Staphylococcus aureus to survive in the absence of lipoteichoic acid

The cell wall of Staphylococcus aureus is composed of peptidoglycan and the anionic polymers lipoteichoic acid (LTA) and wall teichoic acid. LTA is required for growth and normal cell morphology in S. aureus. Strains lacking LTA are usually only viable when grown under osmotically stabilizing conditions or after the acquisition of compensatory mutations. LTA negative suppressor strains with inactivating mutations in gdpP, resulting in an increase in intracellular c-di-AMP levels, have been described previously. Here, we sought to identify factors other than c-di-AMP that allow S. aureus to survive without LTA. LTA-negative strains able to grow in un-supplemented medium were obtained and found to contain mutations in sgtB, mazE, clpX or vraT. The growth improvement through mutations in mazE and sgtB was confirmed by complementation analysis. We also show that an S. aureus sgtB transposon mutant, inactivated for the monofunctional peptidoglycan glycosyltransferase SgtB, displays a 4-fold increase in the MIC towards a number of cell wall-targeting antibiotics, suggesting that alteration in the peptidoglycan structure could help bacteria compensate for the lack of LTA. Muropeptide analysis of peptidoglycan isolated from a WT and sgtB mutant strains did not reveal any sizable alternations in the peptidoglycan structure. In contrast, the peptidoglycan isolated from an LTA-negative ltaS mutant strain showed a significant reduction in the fraction of highly crosslinked peptidoglycan, which was partially rescued in the sgtB/ltaS double mutant suppressor strain. Taken together, these data point towards an important function of LTA in cell wall integrity through its requirement for proper peptidoglycan assembly.\n\nImportanceThe bacterial cell wall acts as primary defence against environmental insults such as changes in osmolarity. It is also a vulnerable structure as defects in its synthesis can lead to growth arrest or cell death. The important human pathogen Staphylococcus aureus has a typical Gram-positive cell wall, which consists of peptidoglycan and the anionic polymers lipoteichoic acid (LTA) and wall teichoic acid. Several clinically relevant antibiotics inhibit the synthesis of peptidoglycan; hence it and teichoic acids are considered attractive targets for the development of new antimicrobials. We show that LTA is required for efficient peptidoglycan crosslinking in S. aureus and inactivation of a peptidoglycan glycosyltransferase can partially rescue this defect, altogether revealing an intimate link between peptidoglycan and LTA synthesis.

microbiology↗