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Aerobic respiration is a biological energy generation process that consumes organic carbon and oxygen. In the ocean, the balance between photosynthesis and respiration is recognized as critical to understanding the ocean's impact on the hydrospheric and atmospheric CO.sub.2. Techniques to determine respiration can be based on inorganic chemistry, electrochemistry, photochemistry, and enzymology. Here, for method comparison, physiological respiration was simultaneously measured by the Winkler method (W), O.sub.2 electrodes (E), and O.sub.2 optodes (O). These techniques detected respiratory O.sub.2 consumption (R), in situ, in dark incubation chambers. Respiratory electron transport system activity measurements detected potential respiration (Ф), biochemically. Leptomysis lingvura, a marine mysid, and Ulva rigida, a species of green algal sea lettuce, were the two organisms tested. Physiological respiration results from each technique were not statistically significantly different (multiple paired Student's t tests, p value > 0.05) and were inside the range of similar published measurements. The mean dry-mass-specific respiration in L. lingvura and U. rigida was 0.147 ± 0.037 and 0.023 ± 0.008 [micro]mol O.sub.2 h.sup.-1 (mg dry mass).sup.-1, n = 9, respectively. The R-to-Ф ratios were different in the two organisms. However, linear regression between R and Ф for L. lingvura and U. rigida was stronger (r.sup.2 = 0.814 and 0.313) than the linear regression between R and dry biomass (r.sup.2 = 0.643 and 0.213). The application of Passing-Bablok regression analysis evidenced the high correlation between the results, and the Bland-Altman analysis examined the average difference ('bias') and limits of agreement between the methods., Author(s): Daniel R. Bondyale-Juez [sup.1] , Theodore T. Packard [sup.1] , M. Ascensión Viera-Rodríguez [sup.1] , May Gómez [sup.1] Author Affiliations: (1) EOMAR, Marine Ecophysiology Group, IU-ECOAQUA, Universidad de Las [...]

The pyruvate dehydrogenase (PDH) multienzyme complex plays a key role in the metabolic interconnection between glycolysis and the citric acid cycle. Transcription of the Escherichia coli genes for all three components of the PDH complex in the pdhR-aceEF-lpdA operon is repressed by the pyruvate-sensing PdhR, a GntR family transcription regulator, and derepressed by pyruvate. After a systematic search for the regulation targets of PdhR using genomic systematic evolution of ligands by exponential enrichment (SELEX), we have identified two novel targets, ndh, encoding NADH dehydrogenase II, and cyoABCDE, encoding the cytochrome bo-type oxidase, both together forming the pathway of respiratory electron transport downstream from the PDH cycle. PDH generates NADH, while Ndh and CyoABCDE together transport electrons from NADH to oxygen. Using gel shift and DNase I footprinting assays, the PdhR-binding site (PdhR box) was defined, which includes a palindromic consensus sequence, ATTGGTNNNACCAAT. The binding in vitro of PdhR to the PdhR box decreased in the presence of pyruvate. Promoter assays in vivo using a two-fluorescent-protein vector also indicated that the newly identified operons are repressed by PdhR and derepressed by the addition of pyruvate. Taken together, we propose that PdhR is a master regulator for controlling the formation of not only the PDH complex but also the respiratory electron transport system.

The nature of epistatic interactions between genes encoding interacting proteins in hybrid organisms can have important implications for the evolution of postzygotic reproductive isolation and speciation. At this point very little is known about the fitness differences caused by specific closely interacting but evolutionarily divergent proteins in hybrids between populations or species. The intertidal copepod Tigriopus californicus provides an excellent model in which to study such interactions because the species range includes numerous genetically divergent populations that are still capable of being crossed in the laboratory. Here, the effect on fitness due to the interactions of three complex III proteins of the electron transport system in [F.sub.2] hybrid copepods resulting from crosses of a pair of divergent populations is examined. Significant deviations from Mendelian inheritance are observed for each of the three genes in [F.sub.2] hybrid adults but not in nauplii (larvae). The two-way interactions between these genes also have a significant impact upon the viability of these hybrid copepods. Dominance appears to play an important role in mediating the interactions between these loci as deviations are caused by heterozygote/homozygote deleterious interactions. These results suggest that the fitness consequences of the interactions of these three complex III-associated genes could influence reproductive isolation in this system.

The evaluation of whether bacteria with higher cell-specific nucleic acid content (HNA) or an active electron transport system are responsible for the bulk of bacterioplankton metabolic activity and also whether the phylogenetic diversity of HNA and CTC (5-cyano-2,3-ditolyl tertazolium chloride)-positive cells differed from the diversity of Bacteria with low nucleic acid content (LNA) are reported. The results show that LNA bacteria are not much different from HNA bacteria in either cell-specific rates of substrate incorporation or phylogenetic composition.

Coenzyme Q (CoQ) or ubiquinone functions as an electron transporter in the electron transport system in both prokaryotes and eukaryotes. The isoprenyl side chain of CoQ is modified in some organisms, especially in fungi, for optimal electron transport performance under various conditions. In this study, we investigated the side chain saturated dihydro CoQ (CoQ10(H2)) in Aureobasidium pullulans EXF-150, Sydowia polyspora NBRC 30562, and naturally isolated Plowrightia sp. A37, all of which are melanized Dothideomycetes species within Ascomycota, and also in filamentous fungi Aspergillus oryzae and A. terreus. Plowrightia sp. A37 produced the rarely synthesized tetrahydro type CoQ10(H4), especially in glucose-rich medium, during extended cultivation in contrast to CoQ10(H2) in time-limited cultivation. Using liquid chromatography–mass spectrometry, we identified demethoxyubiquinone-H2 (DMQ(H2)) as an indicative intermediate that suggests that the side chain saturation of CoQ occurs after the formation of DMQ and not always in the last step as previously considered. [ABSTRACT FROM AUTHOR]

Geldanamycin and its derivatives, inhibitors of heat shock protein 90, are considered potent anticancer drugs, although their biosynthetic pathways have not yet been fully elucidated. The key step of conversion of 4,5-dihydrogeldanamycin to geldanamycin was expected to catalyze by a P450 monooxygenase, Gel16. The adequate bioconversions by cytochrome P450 mostly rely upon its interaction with redox partners. Several ferredoxin and ferredoxin reductases are available in the genome of certain organisms, but only a few suitable partners can operate in full efficiency. In this study, we have expressed cytochrome P450 gel16 in Escherichia coli and performed an in vitro assay using 4,5-dihydrogeldanamycin as a substrate. We demonstrated that the in silico method can be applicable for the efficient mining of convenient endogenous redox partners (9 ferredoxins and 6 ferredoxin reductases) against CYP Gel16 from Streptomyces hygroscopicus . The distances for ligand FDX4-FDR6 were found to be 9.384 Å. Similarly, the binding energy between Gel16-FDX4 and FDX4-FDR6 were -611.88 kcal/mol and -834.48 kcal/mol, respectively, suggesting the lowest distance and binding energy rather than other redox partners. These findings suggest that the best redox partners of Gel16 could be NADPH → FDR6 → FDX4 → Gel16.

Respiration rate (R) and electron transport system (ETS) activity were measured in larvae of four chironomid species, Chironomus thummi (Kieffer), Paratanytarsus austriacus (Kieffer), Procladius (Holotanypus) spp., and Zavrelimyia barbatipes (Kieffer) from three mountain lakes. ETS activity and res­ piration rate, measured at a standard temperature of 20 °C, differed significantly between species (ANOVA: p

There is a mismatch between the effects of two respiratory mechanisms in the nitrogen-fixing bacterium Azotobacter vinelandii: electron transport system and glycolysis. More cytochrome d is synthesized to raise the oxygen uptake rate with increasing oxygen partial pressure. This ensures protection of nitrogenase from molecular oxygen. But the rate of glycolysis also goes high with exposure to excess of glucose. Except for the reinforced electron transport system under higher oxygen partial pressure, there is no system capable of converting the harmful extra glycolytic products.