Microautoradiographic studies on host-parasite interactions II. The exchange of 3H-lysine between Uromyces phaseoli and Phaseolus vulgaris

A new species of anaerobic bacterium that degrades the even-numbered carbon fatty acids, butyrate, caproate and caprylate, to acetate and H₂ and the odd-numbered carbon fatty acids, valerate and heptanoate, to acetate, propionate and H₂ was obtained in coculture with either an H₂-utilizing methanogen or H₂-utilizing desulfovibrio. The organism could be grown only in syntrophic association with the H₂-utilizer and no other energy sources or combination of electron donor and acceptors were utilized. It was a Gram-negative helical rod with 2 to 8 flagella, about 20 nm in diameter, inserted in a linear fashion about 130 nm or more apart along the concave side of the cell. It grew with a generation time of 84 h in co-culture with Methanospirillum hungatii and was present in numbers of at least 4.5×10^-6 per g of anaerobic digestor sludge.     

Growth yield and energy generation in anaerobically-grown Campylobacter spec.

An anaerobic continuous culture study was made with Campylobacter spec. to determine growth yields under various growth conditions. The growth media contained 0.1% (w/v) yeast extract as carbon source. When grown in an aspartate-limited culture Y _asp ^max was 4.6. Inclusion of formate in the culture medium hardly affected the true growth yield. The number of ATP equivalents generated in the fumaratereductase system was 0.66 and the Y _ATP ^max was 7.0. In the nitrate reduction with formate 1.7 ATP equivalents were generated, and a YNO _3- ^max of 12.2 was observed. The true growth yield obtained with a mixture of lactate and aspartate was lower than that found with aspartate alone.     

Trypanosoma brucei: An evaluation of salicylhydroxamic acid as a trypanocidal drug

The chemotherapeutic potential of salicylhydroxamic acid (SHAM) was studied in adult rats infected with a strain of Trypanosoma brucei that kills the rats in about 100 hr. The median lethal dose, administered intraperitoneally in a carboxymethyl-cellulose suspension, is approximately 820 mg/kg body weight for male and 850 mg/kg for female rats. The apparent cause of death is severe depression of the central nervous system.Half-maximal inhibition of O₂ uptake by trypanosomes in vitro requires 15 μM SHAM, whereas 100 μM inhibits over 90%. This inhibitory effect on trypanosome respiration was used as a biological assay for the effective SHAM concentration in rat plasma. After administration of a sublethal SHAM dose to rats, the effective plasma SHAM concentration rose rapidly to about 500 μM and then fell to about 10 μM at 4 hr. Nevertheless, this dose did not significantly affect the survival time of rats infected with T. brucei. Even if, by repeated SHAM administration, the plasma SHAM concentration was kept at around 100 μM for more than 4 hr, no therapeutic effect was observed.These results show that O₂ uptake is not essential for the survival of trypanosomes in rats and they support the idea that bloodstream trypanosomes have an alternative pathway for glycolysis, allowing energy production in the absence of respiration.The possibility that SHAM or other inhibitors of trypanosome respiration could stilll be trypanocidal if used in conjunction with another inhibitor of glycolysis is discussed.     

Activity of phosphorylase in Solanum tuberosum during low temperature storage

Changes in the activity of phosphorylase were measured during storage of potatoes at + 2° when the sugar content rises rapidly and subsequently at + 10° when the accumulated sugar is converted mainly to starch. The observed changes were relatively small and could not be related to any of the components of the phosphorylase system, which was shown to be complex.     

Biotransformation of pregnenolone - 7alpha-3H, progesterone - 7alpha-3H and dehydroepiandrosterone - 7alpha-3H by porcine fetal and maternal adrenal homogenate preparations.

The biotransformation of pregnenolone-7alpha-3H and of progesterone-7alpha-3H by porcine fetal and maternal adrenal homogenates at 56 and 112 days of pregnancy and of dehydroepiandrosterone-7alpha-3H by fetal adrenal homogenates has been investigated in vitro. Both pregnenolone-7alpha-3H and progesterone-7alpha-3H were metabolized extensively by maternal adrenal preparations, the principal radioactive metabolites isolated being cortisol, corticosterone, 11-deoxycortisol, deoxycorticosterone, 11beta-hydroxyprogesterone and androstenedione. In addition, 17alpha-hydroxyprogesterone, 20alpha-dihydroprogesterone and cortisone were formed from both substrates and 17alpha-hydroxypregnenolone and progesterone were formed from pregnenolone. Although essentially the same radioactive metabolites were isolated after incubation of fetal adrenal glands with pregnenolone-7alpha-3H or progesterone-7alpha-3H, a greater proportion of the radioactivity was associated with corticosteroids at 112 days of pregnancy than at 56 days. 11beta-Hydroxyandrostenedione and androstenedione were isolated and identified together with an unknown polar metabolite, after incubation of fetal adrenal tissue with dehydroepiandrosterone-7alpha-3H. These results are discussed in relation to feto-placental steroid biosynthesis and metabolism and the role of the fetal adrenal in the initiation of parturition in the pig.     

Abbau von 14C-, 3H- und 36Cl-markiertem γ-Hexachlorcyclohexan durch anaerobe Bodenmikroorganismen

Zusammenfassung Durch eine anaerobe Mischflora aus Ackerboden wurde -Hexachlorcyclohexan (-HCH) in 4–5 Tagen zu 90% abgebaut. Dabei erfolgte eine schnelle Abspaltung des Chlors in Form von Chloridionen und danach eine Freisetzung des C- und H-Anteiles in Form flüchtiger Verbindungen, in denen kein Chlor und auch kein CO₂ nachzuweisen war.Die Verwendung von ¹⁴C/³H- und ³⁶Cl/³H-doppelmarkiertem -HCH zeigte, daß die Cl- und H-Abspaltung nicht im Verhältnis von 1:1 erfolgte, sondern mehr Cl als H abgespalten wurde. Die flüchtigen Verbindungen enthielten andererseits höhere ¹⁴C- als ³H-Anteile. Gaschromatographische Untersuchungen zeigten ebenfalls eine rasche Verminderung des -HCH und die Bildung verschiedener Metabolite. Es wurde jedoch kein -Pentachlorcyclohexen nachgewiesen. Bei steigenden O₂-Gehalten in der Gasphase verminderte sich der -HCH-Abbau. Jedoch fanden auch noch bei 5% O₂ Chlorabspaltung und die Freisetzung flüchtiger Metabolite statt.-HCH wurde ebenfalls, jedoch langsamer, durch die anaerobe Mischflora abgebaut. Auch hier wurde Chlorid abgespalten, und es traten ebenfalls flüchtige Verbindungen auf, die kein Chlor enthielten.

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Degradation of ¹⁴C-, ³H- and ³⁶Cl-labelled -hexachlorocyclohexane by anaerobic soil microorganisms

Up to 90% of the -Hexachlorocyclohexane (-HCH) applied to an anaerobic mixed bacterial flora enriched from an arable soil were degraded within 4–5 days. Degradation resulted in a rapid release of chloride and in formation of chlorine-free volatile metabolites. CO₂ formation from the molecule was not detected.Investigations with ¹⁴C/³H- and ³⁶Cl/³H double-labelled -HCH indicated that the release of Cl and H did not occur in the ratio of 1:1. More Cl than H was split off. The volatile compounds contained more ¹⁴C than ³H. Gas chromatographic studies also showed the rapid decrease of -HCH and the formation of several metabolites. -Pentachlorocyclohexene was not detected. Increasing O₂-contents in the gas phase of cultures resulted in decreases of the compound's degradation. Release of chloride and of volatile metabolites were observed with O₂ contents in the gas phase up to 5%.-HCH was also, but more slowly as with -HCH, degraded by the anaerobic mixed flora. Chloride was released and volatile, chlorine-free metabolites were found.

     

产电微生物Shewanella菌厌氧呼吸代谢网络研究进展

以模式菌株Shewanella oneidensis MR-1为代表的Shewanella菌属产电微生物广泛分布于自然水体环境中。作为兼性厌氧菌,Shewanella菌除了能进行有氧呼吸外,还能利用多种电子受体进行厌氧呼吸。通过多种细胞色素所组成的复杂电子传递网络,Shewanella菌不仅能利用渗入到周质空间的可溶性电子受体进行厌氧呼吸,更为特殊的是其能够借助电子的跨膜传递实现对胞外不溶性电子受体的异化还原代谢。本文概述了近年来Shewanella菌厌氧代谢途径的研究进展,探讨电子传递网络对Shewanella菌呼吸多样性及环境适应性的影响。     

Anaerobic respiration in the Rhodospirillaceae: characterisation of pathways and evaluation of roles in redox balancing during photosynthesis

Abstract Recent discoveries relating to pathways of anaerobic electron transport in the Rhodospirillaceae are reviewed. The main emphasis is on the organism Rhodobacter capsulatus ** but comparisons are made with Rhodobacter sphaeroides ** f. sp. denitrificans and Rhodopseudomonas palustris . The known electron acceptors for anaerobic respiration in Rhodobacter capsulatus are trimethylamine- N -oxide (TMAO), dimethyl sulphoxide (DMSO), nitrate and nitrous oxide. In each case respiration generates a proton electrochemical gradient and in some cases can support growth on non-fermentable carbon sources. However, the principal objective of this review is to discuss the possibility that, apart from a role in energy conservation, anaerobic respiration in the photosynthetic bacteria may have a special function in maintaining redox balance during photosynthetic metabolism. Thus the electron acceptors mentioned above may serve as auxiliary oxidants: (a) to maintain an optimal redox poise of the photosynthetic electron transport chain; (b) to provide a sink for electrons during phototrophic growth on highly reduced carbon substrates.
Molecular properties of the nitrate reductase, nitrous oxide reductase and a single enzyme responsible for reduction of TMAO and DMSO are discussed. These enzymes are all located in the periplasm. Electrons destined for all three enzymes can originate from the rotenone-sensitive NADH dehydrogenase but do not proceed through the antimycin- and myxothiazol-sensitive cytochrome b/c₁ complex. It is likely, therefor, that the pathways of anaerobic respiration overlap with the cyclic photosynthetic electron transport chain only at the level of the ubiquinone pool. Redox components which might be involved in the terminal branches of anaerobic respiration are discussed.