mBio® An ASM Access® Publication

Foodborne pathogens such as Listeria monocytogenes and Bacillus cereus continue to pose serious threats to global food safety, driving demand for natural, consumer-friendly preservation strategies. Circular bacteriocins, a class of ribosomally synthesized antimicrobial peptides characterized by having covalently linked N- and C-termini, are promising candidates due to their superior stability and broad-spectrum activity. Here we describe pumicyclin A, a novel circular bacteriocin produced by two...

Elevated expression of resistance-nodulation-cell division (RND) drug transporters is commonly observed in clinical isolates of Acinetobacter baumannii, a nosocomial pathogen associated with multidrug-resistant infections. We describe here a CRISPRi platform directed toward identifying essential gene hypomorphs that preferentially change resistance to the fluoroquinolone antibiotic ciprofloxacin in RND pump overproducers. An sgRNA library, including single and double nucleotide mutations...

Klebsiella pneumoniae frequently downregulates or completely loses its capsule. This abolishes infection by capsule-targeting phages but concomitantly may favor infection by phages that exploit non-capsular receptors. Although capsule-targeting mechanisms have been studied in detail, the infection strategies of non-capsular phages remain poorly understood. Here, we analyzed receptor usage across a collection of Webervirus phages and found two contrasting phage-host interaction modes within...

Influenza B virus (IBV) is a significant contributor to annual and severe cases of influenza, particularly in the young and elderly. Late in the 2024-25 Northern Hemisphere influenza season, a surge of IBV cases was identified in the Johns Hopkins Hospital Systems. The IBV responsible for the surge, C.3.1/re, was a clade C.3 virus that had reassorted with clade C.5.1 viruses and acquired the D197N mutation in hemagglutinin, restoring a putative N-linked glycan predicted to mask a key...

Mechanosensitive ion channels of small conductance-like channels (MSL) are conserved in cell-walled organisms and enable cellular responses to mechanical stimuli. Nematode-trapping fungi (NTF) rely on nematode-derived mechanical cues to form specialized predatory structures, including adhesive network and mechanically actuated constricting ring (CR) that rapidly inflate upon nematode contact. However, the sensory mechanisms underlying these processes remain unclear. Here, using the adhesive...

In this study, we found that the enterohemorrhagic Escherichia coli (EHEC) strain EDL933 Δstx1/2 is highly resistant to many phages. The three phage defense systems Zorya II, Druantia III, and DISARM-related Antiviral Defense Array (ARMADA II) are encoded on O-island 172 (OI-172) in strain EDL933. Sequence comparison revealed that the three phage defense systems co-occur in 426 E. coli strains, including 277 O157:H7 isolates and 117 diverse non-pathogenic strains. Efficiency of plating (EOP)...

Bacterial cell morphogenesis is controlled by the synthesis and organization of peptidoglycan and driven by multi-protein complexes, such as the divisome and elongasome. Here, we investigate the role of the Corynebacterium glutamicum DivIVA homolog, Wag31, the elongasome scaffold that is required for polar growth in Corynebacteriales. Conditional depletion of Wag31 results in coccoid-shaped cells, able to divide over several generations, showing that Wag31 is essential for rod shape maintenance,...

In utero transmission and spontaneous fetal death are hallmarks of Rift Valley fever virus (RVFV) infection in pregnant animals. Compounding evidence indicates pregnant individuals are particularly vulnerable to RVFV, as in utero transmission and increased rates of miscarriage have been reported in people infected during pregnancy. Further, human placenta explants are permissive to RVFV infection. Viable vaccine candidates intended for veterinary or human use must protect vulnerable populations,...

Clostridioides difficile is a toxin-producing pathogen that opportunistically infects those with a depleted gut microbiome, often triggered by antibiotic use. C. difficile preferentially utilizes Stickland amino acids, including proline, to promote energy generation and growth for colonization. We evaluated host outcomes from infection with wild-type and ΔprdB mouse-infective C. difficile ATCC 43255 strains to investigate how proline metabolism modulates C. difficile's pathogenesis and...

Infectious viral diseases remain a major and persistent threat to human health, and findings from animal models often translate poorly to clinical applications. Here, we constructed protein interactomes for seven species, including humans, revealing substantial differences in research biases. A random sampling strategy was employed to generate human interactomes, with sizes matched to those of the other six species to ensure cross-species comparability. We found that the clustering of virally...

The Cretaceous-Paleogene (K-Pg) bolide impact caused the extinction of over half of all plant and animal species. The "fungal infection mammalian-selection" (FIMS) hypothesis, first proposed in 2005, suggested that a post-K-Pg fungal bloom created selective pressures that favored the survival and evolutionary radiation of warm-blooded mammals due to their resistance to fungal diseases, while cold-blooded dinosaurs were at an evolutionary disadvantage. Evidence now indicates that dinosaurs were...

When growing bacteria start to reach stationary phase, the nucleotide guanosine tetra-phosphate (ppGpp) accumulates intracellularly and regulates the transition of cells from growth to growth arrest. Because commonly studied bacteria remain viable in stationary phase only briefly under laboratory conditions, the role of ppGpp in sustaining long-term bacterial survival after growth arrest has not been widely studied. Rhodopseudomonas palustris strain CGA009 is a phototrophic alpha-proteobacterium...

Chronic hepatitis B virus (HBV) infection affects more than 250 million people worldwide and markedly increases the risk of terminal liver diseases, including liver cirrhosis and hepatocellular carcinoma. Despite its global impact, HBV exhibits a remarkably narrow host range, with natural infection largely restricted to humans and chimpanzees. This stringent tropism has posed a major barrier to the development of experimentally tractable in vivo models and has limited our ability to study viral...

To enhance its pathogenic potential, Neisseria gonorrhoeae (Gc) pirates zinc from human metal sequestration proteins using TonB-dependent outer membrane transport systems. However, cytoplasmic mechanisms by which Gc adapts to zinc limitation are still uncharacterized. rpmE2 and rpmJ2 transcripts, encoding alternative L31 and L36 ribosomal proteins, respectively, which are not predicted to bind zinc, are significantly more abundant in zinc-limited Gc. In other bacterial species, alternative...

Akkermansia muciniphila is a mucophilic commensal bacterium that significantly impacts metabolic and immune homeostasis. However, the bacterial factors involved in colonization of the gastrointestinal tract are not well understood. Here, we clarify the role of capsular polysaccharides (CPS) in Akkermansia (Akk) colonization. We show that Akkermansia species have multiple cps loci, with cps1 being the most conserved across species. We find that cps1 is regulated by phase variation via invertible...