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Metabolic syndrome (MS) is a cluster of metabolic disorders which have a tight correlation with dysbiosis of gut microbiota (GM) that have to be treated to avoid higher risks for health. In this work, probiotics obtained from healthy cultured GM were provided to rats with metabolic syndrome (MSR) as therapy in treating MS through the correction of dysbiosis. MSR showed obesity, high blood pressure, abnormal blood chemistry parameters and high heart rate respect to control rats (CNTR). Cultivated GM from feces of MSR in media favoring anaerobic species, showed dysbiosis as judged by differences in the 16S rRNA metabarcoding analysis and by affected intermediary metabolism (methane and SCFA production, nutrients consumption and enzyme activities) compared to CNTR. The metabarcoding analysis of cultured healthy GM identified 211 species, which were further transplanted alive in MSR once a week for 9 weeks. Thereafter, in transplanted MSR the excess of Clostridium and Lactobacillus diminished, while Prevotella, Eubacterium, Faecalibacterium and methanogens, among others increased, leading to the recovery of the microbial metabolic capacity. The presence of butyric acid-producing bacteria in the transplanted GM correlated with increased levels of anti-inflammatory cytokines. Therefore, transplanted MSR recovered the normal levels of weight, blood glucose, triglycerides and cholesterol as well as the heart function. Data suggested that the great diversity of species contained in the GM transplanted restored the microbial metabolism, consuming excessive nutrients and secondary metabolites produced by MS. The use of cultivated GM as probiotics may be a safer alternative for the treatment of different diseases., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article, (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The marine archaeon Methanosarcina acetivorans contains a putative NAD  +  -independent d-lactate dehydrogenase (D-iLDH/glycolate oxidase) encoded by the MA4631 gene, belonging to the FAD-oxidase C superfamily. Nucleotide sequences similar to MA4631 gene, were identified in other methanogens and Firmicutes with >90 and 35-40% identity, respectively. Therefore, the lactate metabolism in M. acetivorans is reported here. Cells subjected to intermittent pulses of oxygen (air-adapted; AA-Ma cells) consumed lactate only in combination with acetate, increasing methane production and biomass yield. In AA-Ma cells incubated with d-lactate plus [ 14 C]-l-lactate, the radioactive label was found in methane, CO 2 and glycogen, indicating that lactate metabolism fed both methanogenesis and gluconeogenesis. Moreover, d-lactate oxidation was coupled to O 2 -consumption which was sensitive to HQNO; also, AA-Ma cells showed high transcript levels of gene dld and those encoding subunits A (MA1006) and B (MA1007) of a putative cytochrome bd quinol oxidase, compared to anaerobic control cells. An E. coli mutant deficient in dld complemented with the MA4631 gene, grew with d-lactate as carbon source and showed membrane-bound d-lactate:quinone oxidoreductase activity. The product of the MA4631 gene is a FAD-containing monomer showing activity of iLDH with preference to d-lactate. The results suggested that air adapted M. acetivorans is able to co-metabolize lactate and acetate with associated oxygen consumption by triggering the transcription and synthesis of the D-iLDH and a putative cytochrome bd: methanophenazine (quinol) oxidoreductase. Biomass generation and O 2 consumption, suggest a potentially new oxygen detoxification mechanism coupled to energy conservation in this methanogen., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2023 Elsevier Inc. All rights reserved.)

A challenge in the study of gastrointestinal microbiota (GITm) is the validation of the genomic data with metabolic studies of the microbial communities to understand how the microbial networks work during health and sickness. To gain insights into the metabolism of the GITm, feces from healthy and sick rats with cancer were inoculated in a defined synthetic medium directed for anaerobic prokaryote growth (INC-07 medium). Significant differences between cultures of healthy and sick individuals were found: 1) the consumption of the carbon source and the enzyme activity involved in their catabolism (e.g., sucrase, lactase, lipases, aminotransferases, and dehydrogenases); 2) higher excretion of acetic, propionic, isobutyric, butyric, valeric, and isovaleric acids; 3) methane production; 4) ability to form biofilms; and 5) up to 500 amplicon sequencing variants (ASVs) identified showed different diversity and abundance. Moreover, the bowel inflammation induced by cancer triggered oxidative stress, which correlated with deficient antioxidant machinery (e.g., NADPH-producing enzymes) determined in the GITm cultures from sick individuals in comparison with those from control individuals. Altogether, the data suggested that to preserve the microbial network between bacteria and methanogenic archaea, a complete oxidation of the carbon source may be essential for healthy microbiota. The correlation of 16S rRNA gene metabarcoding between cultures and feces, as well as metabolomic data found in cultures, suggest that INC-07 medium may be a useful tool to understand the metabolism of microbiota under gut conditions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Peña-Ocaña, Hoshiko, Silva-Flores, Maeda, Pérez-Torres, García-Contreras, Gutiérrez-Sarmiento, Hernández-Esquivel, Marín-Hernández, Sánchez-Thomas, Saavedra, Rodríguez-Zavala and Jasso-Chávez.)