A Small Regulatory RNA Generated from the malK 5' Untranslated Region Targets Gluconeogenesis in Vibrio Species

Aminoglycoside uptake, stress, and potentiation in Gram-negative bacteria: new therapies with old molecules

SUMMARYAminoglycosides (AGs) are long-known molecules successfully used against Gram-negative pathogens. While their use declined with the discovery of new antibiotics, they are now classified as critically important molecules because of their effectiveness against multidrug-resistant bacteria. While they can efficiently cross the Gram-negative envelope, the mechanism of AG entry is still incompletely understood, although this comprehension is essential for the development of new therapies in the face of the alarming increase in antibiotic resistance. Increasing antibiotic uptake in bacteria is one strategy to enhance effective treatments. This review aims, first, to consolidate old and recent knowledge about AG uptake; second, to explore the connection between AG-dependent bacterial stress and drug uptake; and finally, to present new strategies of potentiation of AG uptake for more efficient antibiotic therapies. In particular, we emphasize on the connection between sugar transport and AG potentiation.

Both extracellular vesicles from helicobacter pylori-infected cells and helicobacter pylori outer membrane vesicles are involved in gastric/extragastric diseases

Bacterial-derived extracellular vesicles (EVs) have emerged as crucial mediators in the cross-talk between hosts and pathogens, playing a significant role in infectious diseases and cancers. Among these pathogens, Helicobacter pylori (H. pylori) is a particularly important bacterium implicated in various gastrointestinal disorders, gastric cancers, and systemic illnesses. H. pylori achieves these effects by stimulating host cells to secrete EVs and generating internal outer membrane vesicles (OMVs). The EVs derived from H. pylori-infected host cells modulate inflammatory signaling pathways, thereby affecting cell proliferation, apoptosis, cytokine release, immune cell modification, and endothelial dysfunction, as well as disrupting cellular junctional structures and inducing cytoskeletal reorganization. In addition, OMVs isolated from H. pylori play a pivotal role in shaping subsequent immunopathological responses. These vesicles incite both inflammatory and immunosuppressive reactions within the host environment, facilitating pathogen evasion of host defenses and invasion of host cells. Despite this growing understanding, research involving H. pylori-derived EVs remains in its early stages across different domains. In this comprehensive review, we present recent advancements elucidating the contributions of EV components, such as non-coding RNAs (ncRNAs) and proteins, to the pathogenesis of gastric and extragastric diseases. Furthermore, we highlight their potential utility as biomarkers, therapeutic targets, and vehicles for targeted delivery.

Identification of the active mechanism of aminoglycoside entry in V. cholerae through characterization of sRNA ctrR, regulating carbohydrate utilization and transport

The possible active entry of aminoglycosides in bacterial cells has been debated since the development of this antibiotic family. Here we report the identification of their active transport mechanism in Vibrio species. We combined genome-wide transcriptional analysis and fitness screens to identify alterations driven by treatment of V. cholerae with sub-minimum inhibitory concentrations (sub-MIC) of the aminoglycoside tobramycin. RNA-seq data showed downregulation of the small non-coding RNA ncRNA586 during such treatment, while Tn-seq revealed that inactivation of this sRNA was associated with improved fitness in the presence of tobramycin. This sRNA is located near sugar transport genes and previous work on a homologous region in Vibrio tasmaniensis suggested that this sRNA stabilizes gene transcripts for carbohydrate transport and utilization, as well as phage receptors. The role for ncRNA586, hereafter named ctrR, in the transport of both carbohydrates and aminoglycosides, was further investigated. Flow cytometry on cells treated with a fluorescent aminoglycoside confirmed the role of ctrR and of carbohydrate transporters in differential aminoglycoside entry. Despite sequence diversity, ctrR showed functional conservation across the Vibrionales. This system in directly modulated by carbon sources, suggesting regulation by carbon catabolite repression, a widely conserved mechanism in Gram-negative bacteria, priming future research on aminoglycoside uptake by sugar transporters in other bacterial species.

6S RNA-Dependent Susceptibility to RNA Polymerase Inhibitors

Bacterial small RNAs (sRNAs) contribute to a variety of regulatory mechanisms that modulate a wide range of pathways, including metabolism, virulence, and antibiotic resistance. We investigated the involvement of sRNAs in rifampicin resistance in the opportunistic pathogen Staphylococcus aureus. Using a competition assay with an sRNA mutant library, we identified 6S RNA as being required for protection against low concentrations of rifampicin, an RNA polymerase (RNAP) inhibitor. This effect applied to rifabutin and fidaxomicin, two other RNAP-targeting antibiotics. 6S RNA is highly conserved in bacteria, and its absence in two other major pathogens, Salmonella enterica and Clostridioides difficile, also impaired susceptibility to RNAP inhibitors. In S. aureus, 6S RNA is produced from an autonomous gene and accumulates in stationary phase. In contrast to what was reported for Escherichia coli, S. aureus 6S RNA does not appear to play a critical role in the transition from exponential to stationary phase but affects σ^B-regulated expression in prolonged stationary phase. Nevertheless, its protective effect against rifampicin is independent of alternative sigma factor σ^B activity. Our results suggest that 6S RNA helps maintain RNAP-σ^A integrity in S. aureus, which could in turn help bacteria withstand low concentrations of RNAP inhibitors.