Biology subjects

Trojanowski, D.

Publications and source records attributed to Trojanowski, D..

4 recordsLinked to original sources

bioRxiv2026

FtsK with a unique N-terminal extension is involved in coordinating the final steps of chromosome segregation with asymmetrical division in mycobacterial cells

In this study, we identify and functionally characterize a previously unrecognized, conserved N-terminal extension of mycobacterial FtsK (nFtsK) that contributes to the coordination of chromosome segregation with asymmetric cell division. Although FtsK is broadly conserved in bacteria as a late-stage DNA translocase and divisome component, mycobacterial FtsK uniquely contains a long, positively charged, intrinsically disordered N-terminal region. We show that this extension is dispensable for core FtsK functions--including septal localization, DNA translocation, and completion of cell division--but instead modulates the spatial confinement, temporal regulation, and interaction specificity of these processes. Mechanistically, nFtsK mediates specific protein interaction, binds the anionic phospholipids cardiolipin and phosphatidic acid, and exhibits intrinsic affinity for negatively curved membrane. Together, our findings uncover a lineage-specific adaptation that fine-tunes a conserved molecular machine, enhancing the robustness of asymmetric cell division in mycobacteria.

molecular biology↗

bioRxiv2020

Lsr2 is a nucleoid-associated protein that exerts pleiotropic effects on mycobacterial cellular processes

Lsr2 is involved in maintaining chromosome structure in asymmetrically dividing mycobacteria and is essential in the tubercle bacillus (M. tuberculosis) during infection. Here, we report that a lack of Lsr2 profoundly impacts the mycobacterial cell morphology and the properties of the cell envelope resulting in the formation of smooth, short and antibiotics sensitive cells. Lsr2 forms large and dynamic nucleoprotein complexes in vivo and deletion of lsr2 gene exerts a profound effect on the replication time and replisome dynamics. We suggest that the Lsr2 nucleoprotein complexes may contribute to maintaining the proper organization of the newly synthesized DNA. Moreover, we demonstrate that the N-terminal oligomerization domain of Lsr2 is indispensable for the formation of nucleoprotein complexes in vivo. Collectively, our results indicate that Lsr2 exerts a pleiotropic effect on cellular processes and appears to be an attractive target for the development of a novel antitubercular drugs.

microbiology↗

bioRxiv2019

Dynamics of chromosome replication and its relationship to predatory attack lifestyles in Bdellovibrio bacteriovorus

Bdellovibrio bacteriovorus is a small Gram-negative, an obligate predatory bacterium that is largely found in wet, aerobic environments (i.e. soil). This bacterium attacks and invades other Gram-negative bacteria, including animal and plant pathogens. The intriguing life cycle of B. bacteriovorus consists of two phases: a free-living non-replicative attack phase wherein the predatory bacterium searches for its prey, and a reproductive phase, in which B. bacteriovorus degrades a hosts macromolecules and reuses them for its own growth and chromosome replication. Although the cell biology of this predatory bacterium has gained considerable interest in recent years, we know almost nothing about the dynamics of chromosome replication in B. bacteriovorus. Here, we performed a real-time investigation into the subcellular localization of the replisome(s) in single cells of B. bacteriovorus. Our results confirm that in B. bacteriovorus chromosome replication fires only during the reproductive phase, and show for the first time that this predatory bacterium exhibits a novel spatiotemporal arrangement of chromosome replication. The replication process starts at the invasive pole of the predatory bacterium inside the prey cell and proceeds until several copies of the chromosome have been completely synthesized. This chromosome replication is not coincident with the predator-cell division, and it terminates shortly before synchronous predator-filament septation occurs. In addition, we demonstrate that if this lifecycle fails in some cells of B. bacteriovorus, they can instead use two prey cells sequentially to complete their life cycle.\n\nImportanceNew strategies are needed to combat multidrug-resistant bacterial infections. Application of the predatory bacterium, Bdellovibrio bacteriovorus, which kills other bacteria including pathogens, is considered promising for bacterial infections. The B. bacteriovorus life cycle consists of two phases, a free-living, invasive attack phase and an intracellular reproductive phase, in which this predatory bacterium degrades the hosts macromolecules and reuses them for its own growth. To understand the use of B. bacteriovorus as a living antibiotic, it is first necessary to dissect its life cycle including chromosome replication. Here, we present for the first time a real-time investigation into subcellular localization of chromosome replication in a single cells of B. bacteriovorus. This process initiates at the invasion pole of B. bacteriovorus and proceeds until several copies of the chromosome have been completely synthesized. Interestingly, we demonstrate that some cells of B. bacteriovorus require two prey cells sequentially to complete their life cycle.

microbiology↗

bioRxiv2018

Watching antibiotics in action: Exploiting time-lapse microfluidic microscopy as a tool for target-drug interaction studies in Mycobacterium

Spreading resistance to antibiotics and the emergence of multidrug-resistant strains have become frequent in many bacterial species, including mycobacteria. The genus Mycobacterium encompasses both human and animal pathogens that cause severe diseases and have profound impacts on global health and the world economy. Here, we used a novel system of microfluidics, fluorescence microscopy and target-tagged fluorescent reporter strains of M. smegmatis to perform real-time monitoring of replisome and chromosome dynamics following the addition of replication-altering drugs (novobiocin, nalidixic acid and griselimycin) at the single-cell level. We found that novobiocin stalled replication forks and caused relaxation of the nucleoid, nalidixic acid triggered rapid replisome collapse and compaction of the nucleoid, and griselimycin caused replisome instability with subsequent over-initiation of chromosome replication and over-relaxation of the nucleoid. This work is an example of using a microscopy-based approach to evaluate the activity of potential replication inhibitors and provides mechanistic insights into their modes of action. Our system also enabled us to observe how the tested antibiotics affected the physiology of mycobacterial cells (i.e., growth, chromosome segregation, etc.). Because proteins involved in the DNA replication are well conserved among bacteria (including mycobacterial species), the properties of various replication inhibitors observed here in fast-growing M. smegmatis may be easily extrapolated to slow-growing pathogenic tubercle bacilli, such as M. tuberculosis.\n\nSignificanceThe growing problem of bacterial resistance to antibiotics and the emergence of new strains that are resistant to multiple drugs raise the need to explore new antibiotics and re-evaluate the existing options. Here, we present a system that allows the action of antibiotics to be monitored at the single-cell level. Such studies are important in the light of bacterial heterogeneity, which may be enhanced in unfavorable conditions, such as under antibiotic treatment. Moreover, our studies provide mechanistic insights into the action modes of the tested compounds. As combined therapies have recently gained increased interest, it is also notable that our described system may help researchers identify the best combination of antimicrobials for use against infections caused by a variety of bacteria.

microbiology↗