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The extremophile microorganism Thermus scotoductus primarily exhibits aerobic metabolism, though some strains are capable of anaerobic growth, utilizing diverse electron acceptors. We focused on the T. scotoductus K1 strain, exploring its aerobic growth and metabolism, responses to various carbon sources, and characterization of its bioenergetic and physiological properties. The strain grew on different carbon sources, depending on their concentration and the medium's pH, demonstrating adaptability to acidic environments (pH 6.0). It was shown that 4 g L-1 glucose inhibited the specific growth rate by approximately 4.8-fold and 5.6-fold compared to 1 g L-1 glucose at pH 8.5 and pH 6.0, respectively. However, this inhibition was not observed in the presence of fructose, galactose, lactose, and starch. Extracellular and intracellular pH variations were mainly alkalifying during growth. At pH 6.0, the membrane potential (Δψ) was lower for all carbon sources compared to pH 8.5. The proton motive force (Δp) was lower only during growth on lactose due to the difference in the transmembrane proton gradient (ΔpH). Moreover, at pH 6.0 during growth on lactose, a positive Δp was detected, indicating the cells' ability to employ a unique energy-conserving strategy. Taken together, these findings concluded that Thermus scotoductus K1 exhibits different growth and bioenergetic properties depending on the carbon source, which can be useful for biotechnological applications. These findings offer valuable insights into how bacterial cells function under high-temperature conditions, which is essential for applying bioenergetics knowledge in future biotechnological advancements. [ABSTRACT FROM AUTHOR]

After brewing roasted coffee, spent coffee grounds (SCGs) are generated being one of the daily wastes emerging in dominant countries with high rate and big quantity. Escherichia coli BW25113 wild-type strain, mutants with defects in hydrogen (H2)-producing/oxidizing four hydrogenases (Hyd) (ΔhyaB ΔhybC, ΔhycE, ΔhyfG) and septuple mutant (ΔhyaB ΔhybC ΔhycA ΔfdoG ΔldhA ΔfrdC ΔaceE) were investigated by measuring change of external pH, bacterial growth and H2 production during the utilization of SCG hydrolysate. In wild type, H2 was produced with rate of 1.28 mL H2 (g sugar)−1 h−1 yielding 30.7 mL H2 (g sugar)−1 or 2.75 L (kg SCG)−1 during 24 h. In septuple mutant, H2 production yield was 72 mL H2 (g sugar)−1 with rate of 3 mL H2 (g sugar)−1 h−1. H2 generation was absent in hycE single mutant showing the main role of Hyd-3 in H2 production. During utilization of SCG wild type, specific growth rate was 0.72 ± 0.01 h−1 with biomass yield of 0.3 g L−1. Genetic modifications and control of external parameters during growth could lead to prolonged and enhanced microbiological H2 production by organic wastes, which will aid more efficiently global sustainable energy needs resulting in diversification of mobile and fixed energy sources. [ABSTRACT FROM AUTHOR]