title: Redox stress in geobacilli from geothermal springs: Phenomenon and membrane-associated response mechanisms.
abstract: Geobacillus toebii ArzA-8, from Armenian geothermal springs, grew well in nutrient broth. During its growth, changes in pH in opposite directions were observed depending on glucose supplementation. Accordingly, the decrease in the redox potential was determined using titanium-silicate (Eh) and platinum (Eh') electrodes: Eh decreased to -150 ± 3 mV and Eh' to -350 ± 2 mV without glucose; the decrease in these potentials was smaller with glucose. Redox stress due to an oxidizer, K3[Fe(CN)6], or a reducer, dl-dithiothreitol (DTT), inhibited bacterial growth. However, a stimulatory effect of K3[Fe(CN)6] or DTT was observed with or without glucose, respectively. With glucose, the H(+) efflux was sensitive to N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of FoF1FOF1-ATPase and other H(+) translocation mechanisms, but the addition of an oxidizer or reducer suppressed the H(+) efflux. The ATPase activity of membrane vesicles was ~1.3-fold higher in cells grown with glucose compared with cells grown without glucose. DCCD and DTT suppressed ATPase activity in cells grown without glucose, whereas DTT stimulated FOF1-ATPase activity in cells grown with glucose. Thus, G. toebii senses redox stress; this thermophile likely presents specific membrane-associated response mechanisms involving FOF1-ATPase to overcome redox stress and survive; these mechanisms are important for adaptation to extreme environments.
authors.affiliation: Department of Microbiology & Plants and Microbes Biotechnology, Biology Faculty, Yerevan State University, A. Manoogian 1, 0025 Yerevan, Armenia.
authors.forename: Astghik
authors.initials: A
authors.lastname: Ghazaryan
authors.affiliation: Department of Microbiology & Plants and Microbes Biotechnology, Biology Faculty, Yerevan State University, A. Manoogian 1, 0025 Yerevan, Armenia.
authors.forename: Syuzanna
authors.initials: S
authors.lastname: Blbulyan
authors.affiliation: Department of Microbiology & Plants and Microbes Biotechnology, Biology Faculty, Yerevan State University, A. Manoogian 1, 0025 Yerevan, Armenia.
authors.forename: Anna
authors.initials: A
authors.lastname: Poladyan
authors.affiliation: Department of Microbiology & Plants and Microbes Biotechnology, Biology Faculty, Yerevan State University, A. Manoogian 1, 0025 Yerevan, Armenia. Electronic address: Trchounian@ysu.am.
authors.forename: Armen
authors.initials: A
authors.lastname: Trchounian
mesh_terms: D056506:Geobacillus / Q000378:metabolism*; D045482:Hot Springs / Q000382:microbiology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress
keywords: Bacterial bioenergetics; Geobacillus toebii; Proton efflux, the FoF1-ATPase activity; Redox potential, oxidizer and reducer; Stress response; pH