Respiratory Na+ pump and Na+-dependent energetics inVibrio alginolyticus

The marine bacteriumVibrio alginolyticus was found to possess the respiratory Na⁺ pump that generates an electrochemical potential of Na⁺, which plays a central role in bioenergetics ofV. alginolyticus, as a direct result of respiration. Mutants defective in the Na⁺ pump revealed that one of the two kinds of NADH: quinone oxidoreductase requires Na⁺ for activity and functions as the Na⁺ pump. The Na⁺ pump composed of three subunits was purified and reconstituted into liposomes. Generation of membrane potential by the reconstituted proteoliposomes required Na⁺. The respiratory Na⁺ pump coupled to the NADH: quinone oxidoreductase was found in wide varieties of Gramnegative marine bacteria belonging to the generaAlcaligenes, Alteromonas, andVibrio, and showed a striking similarity in the mode of electron transfer and enzymic properties. Na⁺ extrusion seemed to be coupled to a dismutation reaction, which leads to the formation of quinol and quinone from semi-quinone radical.     

The electrochemical proton potential generated by the sulphur respiration of Wolinella succinogenes

Wolinella succinogenes grown on formate and elemental sulphur was found to use the polysulphide derivatives 2,2-tetrathiobispropionate (R₂S₄) or pentathionate (S₅O ₆ ⁼ ) as acceptors for formate oxidation. The specific activities of formate oxidation with these acceptors were similar to those with elemental sulphur. The main reaction products of R₂S₄ reduction were 2,2-dithiobispropionate (R₂S₂) and sulphide. Pentathionate was converted to thiosulphate and some elemental sulphur. The electrochemical proton potential across the cytoplasmic membrane of the bacterium was measured in the steady state of electron transport from formate to R₂S₄. The electrical proportion () of the determined through the distribution of labeled tetraphenylphosphonium cation was obtained as 0.17 Volt. The was zero, when a protonophore was present. The pH-difference across the membrane was negligible. Thus the generated by sulphur respiration is close to that measured earlier with fumarate as the terminal acceptor of electron transport.Abbreviations DMO 5,5-dimethyloxazolidine-2,4-dione - R₂S_n (n=2–5) 2,2-polythiobispropionate - TTFB 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazol - TPP tetraphenylphosphonium cation     

Thiolutin inhibits utilization of glucose and other carbon sources in cells of Escherichia coli

Thiolutin was found to inhibit the utilization of glucose and other growth substrates in Escherichia coli. The inhibition was detected by a sharp drop of the respiration rate after addition of the antibiotic. The actual function affected was allocated to the cytoplasmic membrane of the bacterial cells by the following evidence:

Hyporheic biofilms — a potential food source for interstitial animals

Glass-beads (diam. = 250 μm) were buried 10 cm deep in the sediment of a stream. After an exposure of eight weeks, bacterial densities on the beads varied between 2.7 × 10⁵ and 2.4 × 10⁷/cm², and the length of the fungal mycelium between 0.2 and 5.3 mm/cm². Bacterial densities did not show any correlation with the DOC content of the water, but were positively correlated with respiration on the beads. Fungal mycelium was negatively correlated with water temperature. Acid hydrolysis of stream-exposed beads released sugars and amino acids, whose combined carbon content exceeded that of the microbial cells by a factor of at least 4. Gut extracts of Gammarus tigrinus and Tipula caloptera released amino acids and sugars from stream-exposed beads.     

Functional bioassays utilizing zooplankton: a comparison

Functional zooplankton bioassays based on ingestion, reproduction and respiration are described, with methods for a new ingestion bioassay included. All bioassays are compared using three indices, including the variability of controls, the range of experimental responses, and a listing of contaminants causing inhibition/stimulation of response. The ingestion bioassay showed the greatest range of response, and was sensitive to pesticides, PCBs and heavy metals. It was also commonly characterized by a hormesis response. The reproduction bioassay showed the lowest variability, illustrated a reduced range of response, and was sensitive to nutrients and heavy metals. In one study, the respiration bioassay was sensitive only to PCBs.     

Strain DCB-1 conserves energy for growth from reductive dechlorination coupled to formate oxidation

Strain DCB-1 is a strict anaerobe capable of the reductive dechlorination of chlorobenzoates. The effect of dechlorination on the yield of pure cultures of DCB-1 was tested. Cultures were incubated with formate or H₂ as electron donors and CO₂ as a putative carbon source. Relative to control cultures with benzoate, cultures which dechlorinated 3-chlorobenzoate and 3,5-dichlorobenzoate had higher yields measured both as protein and cell density. On the media tested the apparent growth yield was 1.7 to 3.4 g cell protein per mole Cl^- removed. Dechlorination also stimulated formate oxidation by growing cultures. Resuspended cells required an electron donor for dechlorination activity, with either formate or elemental iron serving this function. Resuspended cells did not require an electron acceptor for formate consumption, but reductive dechlorination of 3CB to benzoate stoichiometrically stimulated oxidation of formate to CO₂. These results indicate that DCB-1 conserves energy for growth by coupling formate, and probably, H₂ oxidation to reductive dechlorination.Non-standard abbreviations 3CB 3-chlorobenzoate - 35DCB 3,5-dichlorobenzoate - PCF Propionibacterium sp. culture fluid     

Respiratory pathways in Agaricus bisporus and Scytalidium thermophilum

Abstract The respiratory pathways of Agaricus bisporus and Scytalidium thermophilum were studied. A. bisporus appeared to possess both a cyanide-sensitive and a cyanide-insensitive respiration while in S. thermophilum the cyande-insensitive respiration was absent. Growth experiments showed the ecological advantage for A. bisporus under conditions where cytochrome mediated respiration is inhibited.     

Components of woody-tissue respiration in young Abies amabilis (Dougl.) Forbes trees

Summary Woody-tissue respiration was measured on five different dates at three to five locations on each of 12 30-year-old Abies amabilis trees. On any given date, temperature-corrected respiration per unit surface area varied 10 to 40-fold between sampling locations. In stems, the two major components of respiration were growth respiration and sapwood maintenance respiration, which were of roughly equal importance during the growing season. There was no evidence of significant cambial maintenance respiration, suggesting that a stand with high bole surface area would not automatically have high respiration. Respiration in branches was much greater than in boles of comparable volume and growth rates, and was significantly correlated with branch height. Branch respiration may include an another significant component in addition to the two seen in bole respiration, possibly associated with carbohydrate mobilization and transport or with CO₂ efflux from the transpiration stream.     

电刺激兔延髓腹侧化学敏感区和压力敏感区对呼吸、血压,的影响及其中枢递质机制

电刺激麻醉兔延髓腹侧化学敏感区头端区引起潮气量(V_T)增加,呼吸频率(f)增快;电刺激压力敏感区(中间区)则使V_T减小,f亦增快。弱刺激时,两者均产生降压反应;刺激增强可诱发双相或升压反应。在出现周期性呼吸时,电刺激化学敏感区可使呼吸节律正常化、V_T增大,而电刺激压力敏感区则导致呼吸暂停。电刺激压力敏感区时,吸气时间(TI)和呼气时间(T_E)均缩短,以T_E变化更明显;由于V_T减小和T_I缩短,V_T/T_I保持相对不变,提示吸气终止的中枢阈值降低。在准备刺激的相应局部预先应用阿托品,可使电刺激化学敏感区产生的通气增强效应翻转,而对电刺激压力敏感区引起的通气抑制无明显影响;用印防己毒素则可选择性消除电刺激压力敏感区的通气抑制和降压效应。本工作表明延髓腹侧存在两个不同的中枢机制,其中化学敏感区产生的通气增强与胆碱能系统有关;压力敏感区产生的通气减弱效应与GABA系统有关。