Project description:The literature has reported the isolation of arsenate-dependent growing microorganisms which lack a canonical homolog for respiratory arsenate reductase, ArrAB. We recently isolated an arsenate-dependent growing bacterium from volcanic arsenic-bearing environments in Northern Chile, Fusibacter sp. strain 3D3 (Fas) and studied the arsenic metabolism in this Gram-positive isolate. Features of Fas deduced from genome analysis and comparative analysis with other arsenate-reducing microorganisms revealed the lack of ArrAB coding genes and the occurrence of two arsC genes encoding for putative cytoplasmic arsenate reductases named ArsC-1 and ArsC-2. Interestingly, ArsC-1 and ArsC-2 belong to the thioredoxin-coupled family (because of the redox-active disulfide protein used as reductant), but they conferred differential arsenate resistance to the E. coli WC3110 ΔarsC strain. PCR experiments confirmed the absence of arrAB genes and results obtained using uncouplers revealed that Fas growth is linked to the proton gradient. In addition, Fas harbors ferredoxin-NAD+ oxidoreductase (Rnf) and electron transfer flavoprotein (etf) coding genes. These are key molecular markers of a recently discovered flavin-based electron bifurcation mechanism involved in energy conservation, mainly in anaerobic metabolisms regulated by the cellular redox state and mostly associated with cytoplasmic enzyme complexes. At least three electron-bifurcating flavoenzyme complexes were evidenced in Fas, some of them shared in conserved genomic regions by other members of the Fusibacter genus. These physiological and genomic findings permit us to hypothesize the existence of an uncharacterized arsenate-dependent growth metabolism regulated by the cellular redox state in the Fusibacter genus.
Project description:The strain WBS, an anaerobic, psychro- and halotolerant bacterium belonging to the genus Fusibacter, was isolated from the littoral bottom sediments of the White Sea, Arctic, Russia. Fusibacter bizertensis WBS grew at temperatures between 8 and 32 °C (optimum growth at 18-20 °C), pH between 5.2 and 8.3 (optimum growth at pH 7.2), and at NaCl concentrations between 0 and 70 g L-1 (optimum growth at 32 g L-1). It reduced sulfate, thiosulfate, and elemental sulfur into sulfide, and, probably, the strain is able to disproportionate thiosulfate. The strain also utilized a wide range of substrates as it is a chemoorganotrophic bacterium. Analysis of the sequenced genome revealed genes for all enzymes involved in the Embden-Meyerhof glycolytic pathway as well as genes for the non-oxidative stage of the pentose phosphate pathway. The presence of genes encoding aldehyde dehydrogenases and alcohol dehydrogenases also suggests that, in addition to acetate, alcohols can also be the fermentation products. The strain possessed superoxide dismutase and peroxidase activities and the ability to consume O2, which is in full accordance with the presence of corresponding genes of antioxidant defense in the genome. The phylogenetic analysis suggested that the strain WBS is the closest relative of Fusibacter bizertensis LTF Kr01T (16S rRNA gene sequence similarity 98.78%). Based on biochemical and genomic characteristics, the strain WBS is proposed to represent a novel aero-, halo- and psychrotolerant strain from the genus Fusibacter, isolated for the first time among its members from cold oxygenated marine bottom sediments.
| S-EPMC10386464 | biostudies-literature
Project description:Microbial diversity from Laguna Interna, Salar de Atacama