Biology subjects

Senges, C. H. R.

Publications and source records attributed to Senges, C. H. R..

2 recordsLinked to original sources

bioRxiv2024

Trans-Translation inhibitors and copper ions synergize for enhanced antibiotic activity

Trans-Translation is the most effective ribosome rescue mechanism and a compelling target for new antimicrobial agents. A recent proteomic study revealed similarities between the responses of Bacillus subtilis to the inhibitors small-molecule inhibitors oxadiazole KKL-40 and tetrazole KKL-55 and divalent cation ionophores, indicating the disturbance of metal homeostasis as potential secondary mechanism of action. Here, we report increased copper levels in KKL-40 and KKL-55-treated B. subtilis. Both inhibitors form copper complexes that enter large unilamellar vesicles. Copper supplementation enhanced the antibacterial activity against B. subtilis by simultaneously increasing inhibitor and copper uptake. The co-treatment of B. subtilis with trans-translation inhibitors and copper concentrations normally benign for trans-translation-competent cells, caused an immediate stalling of growth and translation, as observed at higher KKL-40 and KKL-55 concentrations without copper supplementation. Proteome analysis showed that during translation stalling cells were unable to mount an effective copper toxicity response. Taken together, the synergetic uptake of KKL-40 and KKL-55 with copper leads to a quick-onset translation stalling, preventing B. subtilis from counteracting the toxic effects of rapid copper influx. Significance statementThe challenge of antimicrobial resistance is growing, necessitating an exploration of novel antibiotic targets. Among these, trans-translation has attracted considerable attention due to its ubiquitous presence in bacteria as well as its role in virulence and pathogenesis. Several inhibitors of trans-translation have been identified in a target-based screening using a whole-cell assay. However, recent proteomic profiling studies suggested that the tested trans-translation inhibitors might have an additional mode of action. In this work, we shed light on their previously undiscovered copper ionophore activity and explore the consequences of co-treating B. subtilis with KKL-40 or KKL-55 and CuCl2. This co-treatment results in a rapid antibiotic influx, and, consequently to the stalling of ribosomes, translation, and bacterial growth. Simultaneously, massive amounts of copper accumulate in the cells, the toxic effects of which require a copper stress response to mitigate. However, such a response is averted by the stalled translation. Dual mechanism antibacterial agents are attractive because they are typically associated with slow emergence of resistance. A deep understanding of the complex interplay of KKL-40 and KKL-55 with metal ions will help to fully exploit trans-translation as an antibacterial target and to develop KKL-40 and KKL-55-based antibiotics into novel treatments for bacterial infections.

microbiology↗

bioRxiv2023

Same same but different; The global response of Escherichia coli to five different LpxC inhibitors

A promising but yet clinically unexploited antibiotic target in difficult-to-treat Gram-negative bacteria is LpxC, the key enzyme in the biosynthesis of lipopolysaccharides (LPS), which are the major constituents of the outer membrane. To gain insights into the mode of action of five different LpxC inhibitors, we conducted a comparative phenotypic and proteomic analysis. All five compounds bound to purified LpxC from Escherichia coli. Treatment of E. coli with these compounds changed the cell shape and stabilized LpxC suggesting that the FtsH-mediated turnover is impaired. LpxC inhibition sensitized E. coli to the cell wall antibiotic vancomycin, which typically does not cross the outer membrane. Four of the five compounds led to an accumulation of lyso-PE, a cleavage product of phosphatidylethanolamine (PE), generated by the phospholipase PldA. The combined results suggested an imbalance in phospholipid (PL) and LPS biosynthesis, which was corroborated by the global proteome response to treatment with the LpxC inhibitors. Apart from LpxC itself, FabA and FabB responsible for the biosynthesis of unsaturated fatty acids, were consistently upregulated. Our work also shows that antibiotics targeting the same enzyme do not necessarily elicit identical cellular responses. Compound-specific marker proteins belonged to different functional categories, like stress responses, nucleotide or amino acid metabolism and quorum sensing. These findings provide new insights into common and distinct cellular defense mechanisms against LpxC inhibition. Moreover, they support a delicate balance between LPS and PL biosynthesis with great potential as point of attack for antimicrobial intervention. ImportanceThe alarming spread of antimicrobial resistance among Gram-negative bacteria calls for novel intervention strategies. Inhibitors of LpxC, the first committed enzyme of lipopolysaccharide biosynthesis have been recognized as promising broad-spectrum antibiotics against Gram-negative pathogens. Despite the development of dozens of chemically diverse LpxC inhibitor molecules, it is essentially unknown how bacteria counteract LpxC inhibition. Our study provides comprehensive insights into the bacterial defense strategies against five different LpxC inhibitors. We show that the cellular response of Escherichia coli is compound-specific but shares a common pattern. Inhibition of LpxC is toxic, disrupts membrane integrity, and elicits a stress response, including upregulation of fatty acid biosynthesis proteins. Pre-treatment of E. coli with low doses of LpxC inhibitors increased the sensitivity to the cell wall antibiotic vancomycin suggesting new directions in combination therapies.

microbiology↗