Biology subjects

Suits, L.

Publications and source records attributed to Suits, L..

3 recordsLinked to original sources

bioRxiv2026

Shedding light on YfhS and YjlC: novel effectors of the NADH dehydrogenase activity of the electron transport chain in Bacillus subtilis

Oxidative phosphorylation is the most efficient way of generating ATP in respiring cells. As high energy electrons are the major source of reactive oxygen species their production needs to be carefully calibrated. In most organisms, NADH dehydrogenase serves as the primary source and gateway of electrons. This complex is responsible for oxidizing NADH to NAD+, which liberates two electrons that are then fed into the respiratory chain. In the Gram-positive model bacterium, Bacillus subtilis, a transcription factor (Rex) is utilized to monitor the rise in NADH level and subsequently increase the production of the NADH dehydrogenase Ndh. Thus, the generation of electrons through this pathway is tightly regulated. In this report, we reveal the presence of another independent mechanism to moderate Ndh activity involving a previously uncharacterized protein, YfhS. Additionally, we present the first experimental evidence showing that the functional NADH dehydrogenase is a two-protein complex comprised of a membrane-associated YjlC and the enzyme Ndh. We find that absence of YfhS leads to cell morphology and growth defects that are corrected by spontaneous mutations in ndh. We note that increased production of NADH dehydrogenase complex proteins by itself is not detrimental. However, strikingly, it is lethal in a strain lacking yfhS. These results reveal that YfhS is an important moderator of NADH dehydrogenase activity. We also demonstrate that YfhS and YjlC are interaction partners. A model developed based on our data indicates that YfhS is an important regulator of intracellular NADH concentration. Compounds that target specific microbial (Type II) NADH dehydrogenase, which is absent in human mitochondria, are considered promising drug candidates to help address the threat posed by antibiotic-resistant bacteria. Overall, our data unveiling the importance of YfhS and YjlC in controlling Ndh activity could be harnessed for the development of new therapeutics.

microbiology↗

bioRxiv2025

Staying in the loop to make ends meet: roles and regulation of GlmR in Bacillus subtilis

The metabolic networks of most life forms integrate cost-benefit analysis to properly budget carbon and other essential nutrients through continuous assessment of nutrient availability and environmental threats. Bacillus subtilis is a Gram-positive model bacterium found in diverse ecological niches such as soil, marine environments, and the human gut. As such, B. subtilis cells finetune metabolic pathways by monitoring signals indicating the presence of nutrients and stressors. A highly conserved protein, GlmR, is a key player in rationing carbon for the production of cell envelope precursors. This function of GlmR can be attributed to its role in cell shape regulation and antibiotic resistance. Given its central position in carbon utilization, GlmR is under post-translational regulation by phosphorylation and UDP-N-acetylglucosamine (UDP-GlcNAc) binding. GlmR is also linked to cyclic-di-AMP (c-di-AMP), a nucleotide second messenger involved in stress response. In this study, we probed the importance of GlmR in cell morphogenesis, c-di-AMP signaling, and investigated the physiological significance of post-translational regulation. Our results reveal that cells lacking glmR exhibit: (i) increased susceptibility to tunicamycin, a cell envelope targeting antibiotic; (ii) impaired division site positioning; and (iii) elevated intracellular c-di-AMP concentration. Furthermore, we show that the function of GlmR is finetuned by UDP-GlcNAc binding, phosphorylation, and acetylation. Additionally, we provide evidence showing that the recently discovered enzymatic activity of GlmR is integral for its function. We show that GlmR is a cell width determinant and propose a model suggesting close cooperation with an actin-like protein, MreB. Overall, our studies highlight that GlmR is at the crux of carbon flux with an important role in maintaining cell envelope integrity. IMPORTANCEBacteria must integrate feedback from multiple metabolic processes to efficiently allocate carbon to produce essential building blocks such as nucleotides, amino acids, and cell wall precursors to support life. GlmR is a critical metabolic factor involved in the making of cell envelope precursors in diverse bacterial phyla. In Bacillus subtilis, cells lacking GlmR are deformed and hypersensitive to cell wall targeting antibiotics. As siphoning off too much carbon from other essential processes is detrimental to cell viability, GlmR activity is tightly regulated. Here we report that absence of GlmR leads to aberrant placement of cytokinetic machinery and an increase in the levels of cyclic-di-AMP, a nucleotide second messenger that assists in the cell wall stress response. We also show that GlmR function is post-translationally finetuned by phosphorylation and acetylation. Furthermore, our data reveals that the catalytic activity of GlmR is required for its function. Thus, the activity of GlmR is tightly calibrated through multiple means for efficient carbon utilization.

microbiology↗

bioRxiv2025

Molecular response to the non-lytic peptide bac7 (1-35) triggers disruption of Klebsiella pneumoniae biofilm

Klebsiella pneumoniae is becoming increasingly difficult to treat as multidrug-resistant (MDR) strains become more prevalent. The formation of biofilm heightens this threat by embedding bacterial cells in a polysaccharide-rich matrix that limits antibiotic penetration. Here we dissect the anti-biofilm bovine host-defense cathelicidin peptide fragment bac7 (1-35), exploring its anti-biofilm mechanism, evaluating its ability to curb dissemination of hypervirulent K. pneumoniae, and testing its breadth of activity against diverse clinical isolates. Transcriptomic profiling revealed that bac7(1-35) simultaneously compromises the bacterial membrane and inhibits ribosomal function, a dual assault that precipitates rapid biofilm collapse and blocks bacterial spread. Further, the peptide eradicated biofilms produced by the strongest MDR clinical isolates in the Multidrug-Resistant Organism Repository and Surveillance Network (MRSN) diversity panel. Although bac7 (1-35) kills bacterial cells via a cytosolic mechanism, membrane interaction profiles varied among MRSN isolates, correlating with differential peptide translocation. In a delayed-treatment murine skin-abscess model, bac7 (1-35) halted in vivo dissemination of the hypervirulent strain NTUH-K2044. Collectively, these results delineate a multifaceted mode of action for bac7 (1-35) and underscore its therapeutic promise against biofilm-associated MDR K. pneumoniae infections. Author SummaryKlebsiella pneumoniae is a top-priority pathogen for new therapies, with many strains already approaching pan-drug resistant status. Biofilm formation further complicates treatment, yet biofilm-active therapeutics have not reached the clinic, in part because we still lack a detailed understanding of how to disrupt these impenetrable structures. Antimicrobial peptides are promising candidates and have shown biofilm-disruption potential. Here we provide mechanistic insight into how a host defense peptide dismantles pre-formed K. pneumoniae biofilms. We find that the peptides dual targeting of bacterial membranes and ribosomes triggers dispersal from the biofilm state and concomitantly downregulates factors required for surface attachment and extracellular matrix production. This mechanism involves a protein that, to our knowledge, has not been characterized in K. pneumoniae. Our findings reveal a switch that can be leveraged to reprogram biofilm maintenance toward dispersal in K. pneumoniae, advancing the path to peptide-based antibiofilm therapeutics.

microbiology↗