Gut bacteria are important in causing inflammatory bowel diseases. By combining the results from published studies we have identified the key changes in these bacteria that might help us develop new d...

A popular disk diffusion method was recently revisited by EUCAST (The European Committee on Antimicrobial Susceptibility Testing) and CA-SFM (Antibiog…

At the onset of inflammatory bowel disease, the gut microbiome shows a clear loss of beneficial, obligate anaerobic bacteria that help digest complex carbohydrates, and a rise in oxygen-tolerant bacteria, including species that normally live in the mouth. These shifts were detected in newly diagnosed people with Crohn’s disease and ulcerative colitis before any treatment, across a combined dataset of more than 1,700 participants from 11 countries.

Patients experience significant changes in gut bacteria at the onset of inflammatory bowel disease (IBD), a new international study has found—offering new hope for earlier diagnosis and future treatments.

Locally advanced rectal cancer involves multimodality treatment that combines 5-fluorouracil (5-FU) based chemotherapy, chemoradiation and surgical resection. Total neoadjuvant therapy and radiation…

Abstract. Over the past two decades, metagenomics has greatly expanded our understanding of microbial phylogenetic and metabolic diversity. However, most m

Diverse microorganisms couple the oxidation of carbon monoxide gas (CO) to the reduction of protons, producing hydrogen gas (H2). This energy-conserving process is mediated by the nickel-containing CO dehydrogenase/energy-converting hydrogenase (Ni-CODH/ECH). Yielding only a small supply of energy, the physiological role of this process at environmentally relevant CO levels remains unresolved. Here, we show that Ni-CODH/ECH enables metabolically flexible facultative anaerobes within the Anoxybacillaceae to survive electron acceptor limitation. Analysis of 387 Anoxybacillaceae genomes revealed that Ni-CODH/ECH had a patchy distribution and, with one exception, was mutually exclusive with the aerobic molybdenum-containing CODH. Culture experiments using the three isolates ( Parageobacillus sp. G301, P. thermoglucosidasius NBRC 107763, and Thermolongibacillus altinsuensis B1-1) demonstrated that CO-dependent proton respiration is activated during stationary phase when exogenous electron acceptors are limiting, enhancing cell density 1.2-to 1.5-fold under 25% CO, whereas no effect was observed in a Ni-CODH knockout (Δ cooCSF ) strain. RNA-seq analysis of strain G301 under twelve conditions revealed that Ni-CODH genes reached 2,000–12,500 TPM (top 0.2–1.9% of all genes) during stationary phase, independent of CO presence, under the predicted control of the redox-dependent transcriptional repressor Rex. Δ cooCSF cultures accumulated more trace CO than the wild-type, suggesting trace CO uptake by the wild-type. Thus, Ni-CODH/ECH is a redox-regulated auxiliary energy-conservation system that supports adaptation to electron acceptor limitation. Given the continual environmental supply of the two substrates for this enzyme, we propose CO-dependent proton respiration is a dependable way for metabolically flexible microorganisms to stay energized in spatiotemporally variable environments. Significance statement Microorganisms are frequently challenged to survive in environments where both energy sources and electron acceptors are limited. We reveal that facultative anaerobes activate a respiratory process that utilizes carbon monoxide (CO) and protons to survive under electron acceptor limitation. This hydrogenogenic CO-oxidizing reaction, termed CO-dependent proton respiration, is catalyzed by an ancient and minimal complex, the nickel-containing CO dehydrogenase/energy-converting hydrogenase. Although the reaction yields barely enough energy to translocate protons, this complex provides a reliable lifeline by extracting energy from trace CO and protons that are ubiquitous in nature, even when other electron acceptors are depleted. The widespread distribution of this complex across bacteria and archaea suggests that it provides a universal adaptive advantage for life under energy-limited conditions. ### Competing Interest Statement The authors have declared no competing interest. Japan Society for the Promotion of Science, https://ror.org/00hhkn466, JP16H06381 Institute for Fermentation, https://ror.org/05nq89q24, L-2021-1-002, G-2024-1-011

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Anaerobes are bacteria that thrive in environments lacking oxygen. They are part of normal flora but can cause disease when introduced into sterile sites. Key anaerobes include Clostridium, Bacteroides, Fusobacterium, and Actinomyces, known for producing foul-smelling infections and gas formation.

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