The relationship between hydrogen metabolism,sulfate reduction and nitrogen fixation in sulfate reducers

Summary Hydrogenase and nitrogenase activities of sulfate-reducing bacteria allow their adaptation to different nutritional habits even under adverse conditions. These exceptional capabilities of adaptation are important factors in the understanding of their predominant role in problems related to anaerobic metal corrosion. Although the D₂–H⁺ exchange reaction indicated thatDesulfovibrio desulfuricans strain Berre-Sol andDesulfovibrio gigas hydrogenases were reversible, the predominant activity in vivo was hydrogen uptake. Hydrogen production was restricted to some particular conditions such as sulfate or nitrogen starvation. Under diazotrophic conditions, a transient hydrogen evolution was followed by uptake when dinitrogen was effectively fixed. In contrast, hydrogen evolution proceeded when acetylene was substituted as the nitrogenase substrate. Hydrogen can thus serve as an electron donor in sulfate reduction and nitrogen metabolism.     

Occurrence of diamine oxidase in the apoplast of pea epicotyls

Most of the diamine oxidase (EC 1.4.3.6) present in pea (Pisum sativum L. cv. Rondo) epicotyls is found in the fluid obtained by centrifuging pea epicotyl sections previously infiltrated under vacuum with a buffer solution. No detectable amount of the cytoplasmic enzyme glucose-6-phosphate dehydrogenase is present in this fluid, showing that there is very little contamination by cell contents. Polyacrylamide-gel electrophoresis and specific-activity data indicate that diamine oxidase is the most plentiful protein in the extracellular solution obtained from pea epicotyl sections and that an active process is involved in the selective transfer of the enzyme outside the cell. The possible involvement of diamine oxidase in the supply of H₂O₂ to peroxidase-catalyzed reactions occurring inside the cell wall is discussed.Abbreviations DAO diamine oxidase - Glc6P glucose-6-phosphate     

Copper ions and hydrogen peroxide form hypochlorite from NaCl thereby mimicking myeloperoxidase

Sea urchins have elaborated multiple defenses to assure monospermic fertilization. In this work, we have concentrated on a study of the mechanism(s) by which hydrogen peroxide (H₂O₂) prevents polyspermy in Arbacia punctulata. We found that it is not H₂O₂ but probably hypochlorous acid/hypochlorite (HOCl/OCl^?) derived from H₂O₂ that is toxic to the supernumerary sperm. The spermicidal activity of H₂O₂ is potentiated by at least one order of magnitude by cupric ions (Cu²⁺). This increased toxicity is not due to the formation of hydroxyl radicals (·OH) because ·OH scavengers did not counteract the activity of Cu²⁺. More-over, substitution of Cu²⁺ by ferrous ions (Fe²⁺), which are known to cause formation of ·OH from H₂O₂, had no effect on fertilization even at 10²?10³ times higher concentrations. In contrast, 3-amino-1,2,4-triazole (AT), an HOCl/OCl^? scavenger, totally reversed the toxic effects of Cu²⁺. Furthermore, we found that HOCl/OCl^? is generated in solutions of H₂O₂ and Cu²⁺ in the presence of 0.5 M NaCl and that its accumulation is abolished by AT. Thus it is possible that the antifertility properties of copper are due to its ability to mediate formation of HOCl/OCl^?. HOCl/OCl^? generated by Cu²⁺ from H₂O₂ and Cl^?, a low concentration of exogenously added HOCl/OCl^?, or increased concentrations of H₂O₂ has similar inhibitory effects on the fertilization process in sea urchins. Therefore, we suggest that polyspermy is prevented by the action of a myeloperoxidase that affects the formation of HOCl/OCl^? from the Cl^? present in sea water through reaction with H₂O₂ generated by the newly fertilized egg.     

Hydrogen-peroxide-scavenging systems within pea chloroplasts

The subcellular distribution of ascorbate peroxidase and glutathione reductase (EC 1.6.4.2) in pea leaves was compared with that of organelle markers. Enzyme distribution was found to be similar to that of the chloroplast enzyme NADPH-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13). Isolated chloroplasts showed a close correlation between intactness and the percentage of enzyme activity recovered. Chloroplasts of 85% intactness were found to contain a high proportion of leaf dehydroascorbate reductase activity (EC 1.8.5.1), 10% of leaf glutathione and 30% of leaf ascorbate. These results are discussed in relation to the potential role of chloroplast antioxidant systems in plant resistance to environmental and other stress conditions.Abbreviations GSH reduced glutathione - GSSG oxidized glutathione - NADPH-GPD glyceraldehyde-3-phosphate dehydrogenase - SOD superoxide dismutase     

A practical approach for quantitating specific mRNAs by solution hybridization

The preparation and use of a specific cDNA probe for quantitating mRNA by solution hybridization is described. Cloned DNA sequences are nick translated, denatured, hybridized to single-stranded M13 clones containing message strand (mDNA) sequences, and separated chromatographically on Bio-Gel A50 under first native and then denaturing conditions to yield a single-stranded cDNA probe. The details of a solution hybridization assay in which the single-stranded cDNA is used to quantitate mRNA in total nucleic acid samples are described. As little as 0.5 pg of mRNA can easily be detected within a day of sample isolation. Thus, the assay is both rapid and sensitive and can be used to measure RNAs complementary to any cloned DNA sequence. It is ideally suited to situations when accurate quantitation of multiple samples is anticipated.     

Analysis of retinal and 3-dehydroretinal in the retina by high-pressure liquid chromatography

A sensitive analytical method was developed in order to study the rhodopsin-porphyropsin system in the eye. Oximes of 11-cis-retinal, all-trans-retinal, 11-cis-3-dehydroretinal, and all-trans-3-dehydroretinal were determined quantitatively by high-pressure liquid chromatography. This method was applied to the analysis of retinal and 3-dehydroretinal in the retinas of bullfrog and goldfish. The results agreed with those obtained from the bleaching kinetics of visual pigment extracted with detergent. A reliable result is obtained if the tissue contains more than 5 pmol of retinal (or 3-dehydroretinal). The chromophore composition could be determined in the eye of a small freshwater prawn, Palaemon pancidence, using 50 pmol of 11-cis-retinal and no 3-dehydroretinal.     

A chemiluminescent method for measurement of activated oxygen forms in biological fluids and homogenates

A chemiluminescent method for measuring the concentration of activated oxygen species (O₂² and H₂O₂) is described. Its main features are: high sensitivity (10^?9 M H₂O₂), its applicability to systems with high optical absorbance in the visible spectral region, a wide linear dynamic range, and the possibility for recording the kinetics of the processes, in which activated oxygen species are involved.     

Taxonomic studies on some gram-positive coryneform hydrogen bacteria

Recently isolated coryneform hydrogen bacteria were investigated under taxonomical aspects. Strains 7 C, RH 10, and 14 g are characterized by the snapping type of cell division, 68.5 to 69.7% GC content, dl-diaminopimelic acid in the cell wall, content of metachromatic granules, weak utilization of sugars and inhibitory effect of citrate. The strains are placed to the group 1—genus Corynebacterium—of the classification of coryneform bacteria of Yamada and Komagata (1972) and the name Corynebacterium autotrophicum sp.nov. is proposed.Strains 11 X and RH 12 are characterized by the bending type of cell division, a GC content of 70.2 and 70.5%, ll-diaminopimelic acid in the cell wall, absence of metachromatic granules, utilization of several sugars and no changes in cell morphology by citrate. The strains have to be placed to group 6 of coryneform bacteria.     

Role of Hydroxyl Radicals in Escherzchza Colz Killing Induced by Hydrogen Peroxide

Escherichia coli lethality by hydrogen peroxide is characterized by two modes of killing. In this paper we have found that hydroxyl radicals (OH -) generated by H₂O₂ and intracellular divalent iron are not involved in the induction of mode one lethality (i.e. cell killing produced by concentrations of H₂O₂ lower than 2.5 mM). In fact, the OH radical scavengers, thiourea, ethanol and dimethyl sulfoxide, and the iron chelator, desferrioxarnine, did not affect the survival of cells exposed to 2.5mM H₂O₂. In addition cell vulnerability to the same H₂O₂ concentration was independent on the intracellular iron content. In contrast, mode two lethality (i.e. cell killing generated by concentrations of H₂O₂ higher than 10mM) was markedly reduced by OH radical scavengers and desferrioxamine and was augmented by increasing the intracellular iron content.

It is concluded that OH. are required for mode two killing of E. coli by hydrogen peroxide.     

水稻不育花药中H_2O_2的积累与膜脂过氧化的加剧

水稻7017、二九矮细胞质雄性不育系及其保持系花药的POD,CAT和SOD活性研究的结果表明,单核早期时不育及可育花药的酶活性差异不明显,单核晚期、二核及三核期的不育花药显著低于可育花药。在不育花药中缺少两条Cu-Zn SOD同工酶带,而且O_2~ 产生效率为可育的4.1～5.5倍,并有H_2O_2和MDA的积累。不育花药中H_2O_2的积累和膜脂过氧化的加剧可能与花粉败育有关。