Microbial Fossils in the 2.63 Ga Jeerinah Formation,Western Australia—Evidence of Microbial Oxidation

A diamond drill core from the upper part of the Jeerinah Formation (～2.63 Ga), underlying the Hamersley Group, deposited at a time when the oxygen concentrations in the marine environment were extremely low, was examined for microbial fossils. The paper presents organo-mineral structures in the form of twisted stalks produced by bacteria being present in the laminated black carbonaceous shale sediments. These twisted stalks are organo-mineral structures produced by microaerophilic Fe(II)-oxidizing-type bacteria such as Gallionella and/or Mariprofundus that are active at very low-oxygen concentrations, thus providing evidence for oxygen being present in the marine environment at 2.63 Ga.     

Oxygen consumption of the aquatic leaf beetles Macroplea mutica and Macroplea appendiculata is low and not influenced by salinity

Leaf beetles of the genus Macroplea live permanently under water. Species‐specific preferences for either freshwater or brackish water are available in the literature. To detect potential physiological differences, the oxygen consumption of Macroplea mutica and Macroplea appendiculata from habitats with differing salinities is measured at two different salinities (0 and 10). The specific oxygen consumption does not depend on oxygen saturation of the water (values in the approximate range of 25–100% occur during the experiments). There is no difference between species or sampling locations. Similarly, the salinity during the measurements does not affect the oxygen consumption of the beetles, either when compared as salinity per se (0 versus 10), or when classified as home salinity or atypical salinity. Comparisons with other chrysomelid beetles and aquatic insects (using available published data) reveal that the two Macroplea species have relatively low metabolic rates. This finding is discussed in the light of activity patterns and morphology, especially the reduction of flight muscles, which comprise a highly metabolically active tissue.     

Occurrence of cytochrome P450 in continuous cultures of Saccharomyces cerevisiae

Summary Cytochrome P450 of Saccharomyces cerevisiae is an inducible enzyme system. Hitherto, its induction was related to semi-anaerobic culture conditions and high glucose concentrations in the growth medium respectively. Since glucose and oxygen are main regulatory effectors in this yeast, the relationship between the occurrence of cytochrome P450 and these two effectors was established in continuous culture. At glucose-derepressed conditions it was not possible to induce the formation of cytochrome P450 by oxygen limitation alone. The oxygen supply had to be decreased to a level where glucose repression also became active. At glucose-repressed conditions cytochrome P450 was obtained in good yield (3 to 5 pmol per mg dry cell weight) below a dissolved oxygen tension of appproximately 15%. There was a correlation between the content of mitochondrial cytochromes and that of cytochrome P450. The presence of mitochondrial cytochromes was reciprocal with cytochrome P450 when its content was increased by lowering the dissolved oxygen tension.     

Cellular responses to elevated light levels in Fucus spiralis embryos during the first days after fertilization

Cellular responses of 1‐, 2‐ and 4‐d‐old Fucus spiralis embryos subjected to a single dose of elevated photosynthetically active photon flux density (PPFD), with or without ultraviolet (UV) radiation, were investigated by measuring the effects on the effective quantum yield of photosystem II (ΔF / F_m′) and intracellular production of active oxygen species (AOS). Production of AOS was determined by the in vivo conversion of 5‐(and‐6)‐chloromethyl‐2′,7′‐dichlorodihydrofluorescein diacetate (CM‐DCFH₂‐DA) to the fluorescent compound dichlorofluorescein (DCF) using confocal laser scan microscopy (CLSM) and image analysis. The role of xanthophyll cycle pigments in photoprotection was also assessed. A rapid decline in ΔF / F_m′ was observed under all elevated light conditions. A correlation was found between non‐photochemical quenching and the de‐epoxidation ratio zeaxanthin/(zeaxanthin + violoxanthin). Active oxygen formation increased with PPFD and was higher in older embryos and when UVB was present. Two photoinhibition responses were recognized: (i) a rapid decline of the PSII yield due to the violoxanthin–zeaxanthin cycle (photoprotection), and (ii) a slower second‐phase decline, correlated with active oxygen production. Electron transport rate (ETR) increased with embryo age, and was correlated with AOS production. As a result of enhanced AOS production, there was a slow recovery of the PSII yield, in particular with increased effective UV dose. In general, embryos were able to recover from the imposed light conditions, but UVB had a more damaging effect. Overall, our data suggest that under natural conditions, embryos of F. spiralis are susceptible to elevated light levels, and that UVB radiation is an important stress factor.     

Respiratory functions of the blood in the limpet Siphonaria zelandica (Gastropoda: Pulmonata)

Abstract

The respiratory pigments myoglobin and haemocyanin were characterised in the marine pulmonate Siphonaria zelandica (Quoy & Gaimard) and their roles in an oxygen transfer system were postulated. In air, when the animals were active, oxygen was transported from a simple diffusion lung by haemocyanin in the blood which had a half-saturation value of 12.7 mm Hg at pH 7.2 and 25°c. At pH 7.6 the oxygen affinity decreased to 17.3 mm Hg, indicating a reverse Bohr effect which might be expected to facilitate oxygen uptake in the lung during bursts of activity at low tide. A high oxygen-combining capacity of buccal mass myoglobin (21.2 vols %) indicated a role of oxygen storage during bursts of feeding activity. The distribution of carbonic anhydrase in various tissues was consistent with a transfer system facilitating the release of metabolic carbon dioxide from the buccal mass.     

Retracted: Tusk shells in trouble? Physiology and behavior in response to changing temperature in a scaphopod (Mollusca: Scaphopoda: Dentaliida)

Scaphopods (tusk shells) are infaunal marine predators that occur at locally high densities in coastal and deep‐sea mud habitats, and as consumers of foraminifera they are important in carbon cycling. We investigated oxygen metabolism and burying behavior of the scaphopod Rhabdus rectius and its responses to altered temperatures. These are the first measurements of oxygen uptake rates for any member of this taxonomic class. In response to elevated temperatures, oxygen uptake rates increased, but the ability of animals to bury themselves in sediment was compromised. Female scaphopods were significantly larger than males and, when corrected for body mass, oxygen uptake rates were consistently higher for female individuals than for males. This is consistent with previous anecdotal observations of females in other scaphopod species being larger and potentially more active. In conditions of declining oxygen availability, individuals of Rhabdus rectius showed strong oxyregulatory ability by maintaining the same oxygen uptake rate displayed in normoxic conditions. The ability to maintain normal metabolic functioning even in conditions of oxygen limitation would benefit a species living in a benthic environment that may be prone to temporary or transient anoxic events. Yet the decrease in normal escape response in moderately elevated temperatures indicates these animals may be at risk from rising sea temperatures.     

Metabolic flexibility of SUP05 under low DO growth conditions

Chemoautotrophic bacteria from the SUP05 clade often dominate anoxic waters within marine oxygen minimum zones (OMZs) where they use energy gained from the oxidation of reduced sulfur to fuel carbon fixation. Some of these SUP05 bacteria are facultative aerobes that can use either nitrate or oxygen as a terminal electron acceptor making them ideally suited to thrive at the boundaries of OMZs where they experience fluctuations in dissolved oxygen (DO). SUP05 metabolism in these regions, and therefore the biogeochemical function of SUP05, depends largely on their sensitivity to oxygen. We evaluated growth and quantified differences in gene expression in Ca. T. autotrophicus strain EF1 from the SUP05 clade under high DO (22 μM), anoxic, and low DO (3.8 μM) concentrations. We show that strain EF1 cells respire oxygen and nitrate and that cells have higher growth rates, express more genes, and fix more carbon when oxygen becomes available for aerobic respiration. Evidence that facultatively aerobic SUP05 are more active and respire nitrate when oxygen becomes available at low concentrations suggests that they are an important source of nitrite across marine OMZ boundary layers.     

The effect of activity on oxygen consumption,oxygen debt,and heart rate in the lizardsVaranus gouldii andsauromalus hispidus

Summary Oxygen consumption and heart rate were measured during rest and activity in the lizardsVaranus gouldii andSauromalus hispidus. Oxygen debt was calculated from postactive oxygen consumption. Standard metabolic rates of the two animals are similar butVaranus consumes much more oxygen during activity than doesSauromalus (Fig. 1–3). The latter has a constant active metabolic rate above 30 ° C and accumulates a large oxygen debt, which is repayed slowly (Fig. 4).Varanus recovers rapidly from activity (Fig. 5), presumably because of the smaller lactacid debt incurred. Heart rate increment inSauromalus is high (Fig. 8). This variable cannot be responsible for the limitation of active oxygen consumption; calculations of oxygen pulse suggest that an inability to increase A-V difference and/or stroke volume are implicated (Fig. 9).Varanus have evolved mechanisms to sustain high levels of oxygen consumption superior to those of other reptiles investigated. The role of anaerobiosis in the biology of both animals is discussed.     

Control of dinitrogen fixation in ammonium-assimilating cultures of Azotobacter vinelandii

Azotobacter vinelandii was grown at constant growth rate in a chemostat with different molar ratios of sucrose to ammonium (C/N) in the influent media. Both compounds were consumed at essentially the same ratios as were present in the influent media. At low (C/N)-ratios, the cultures were ammonium-limited. At increased (C/N)-ratio ammonium-assimilating cultures additionally began to fix dinitrogen. The (C/N)-ratio at which nitrogenase activity became measurable, increased when the ambient oxygen concentration was increased. Immunoblotting revealed the appearance of nitrogenase proteins when the activity became detectable. Nitrogenase activity as determined either by acetylene reduction or by total nitrogen fixation gave constant relative activities of 1:3.8 (mol of N₂ fixed per mol of acetylene reduced) under all sets of conditions used in this investigation. In spite of the oxygen dependent variation of the (C/N)-ratio, nitrogenase became active when the ammonium supply was less than about 14 nmol of ammonium per g of protein. This suggests that oxygen was not directly involved in the onset of dinitrogen fixation.     

水体溶氧影响陆生植物喜旱莲子草(Alternanthera philoxeroides)和牛鞭草(Hemarthria altissima)对完全水淹的耐受力

溶氧是水环境中一个重要的环境因子,为了探讨水中的溶氧含量水平是否会对陆生植物的耐淹能力造成影响,研究了陆生植物喜旱莲子草(Alternanthera philoxeroides)和牛鞭草(Hemarthria altissima)在遭受不同溶氧含量水体完全淹没后的生长表现、存活情况和非结构碳水化合物的变化。实验结果表明:(1)水体中的溶氧含量显著影响了处于完全水淹环境中的喜旱莲子草和牛鞭草的存活。受高溶氧水体完全水淹的喜旱莲子草和牛鞭草主茎的完好程度和存活叶的数量均显著高于遭受低溶氧水体完全水淹的喜旱莲子草和牛鞭草,喜旱莲子草和牛鞭草在高溶氧水体完全水淹后的生物量比低溶氧水体完全水淹后要高;(2)水体中的溶氧含量显著影响了处于完全水淹环境中的喜旱莲子草和牛鞭草的生长,受高溶氧水体完全水淹的喜旱莲子草主茎伸长生长和不定根生长显著强于受低溶氧水体完全水淹的喜旱莲子草,在不定根的生长上牛鞭草也具有同样的表现。(3)高溶氧水环境有利于减小被完全淹没的喜旱莲子草和牛鞭草的碳水化合物消耗,两种植物在受高溶氧完全水淹后体内具有的非结构性碳水化合物含量均比受低溶氧完全水淹后高。(4)喜旱莲子草比牛鞭草能更好地耐受完全水淹,当处于低溶氧完全水淹时表现得更为明显,本研究表明入侵物种喜旱莲子草比本地物种牛鞭草具有更强的环境适应能力和水淹耐受能力。     

Responses of Active Ammonia Oxidizers to Eutrophication and Oxygen Statuses in Taihu Freshwater Sediments

Abstract

Here, we employed DNA-based stable isotope probing (SIP) and molecular biology methods to investigate active ammonia oxidizer communities in suboxic sediments (0 to –2?cm) at the micromolar oxygen level and layers (–2 to –5?cm) at nanomolar oxygen concentrations from meso-eutrophic and light-eutrophic locations in Taihu Lake. The results revealed that ammonia-oxidizing archaea (AOA) were less active in the anoxic layer of meso-eutrophic sites, while ammonia-oxidizing bacteria (AOB) were less active in suboxic sediments of light-eutrophic sites after 8?weeks of incubation. The active AOA in the meso- and light-eutrophic sediments belonged to the Nitrosopumilus, Nitrosotalea, and Nitrososphaera clusters and the Nitrosopumilus and Nitrososphaera clusters, respectively, with Nitrosopumilus cluster as the predominant AOA, which took up a higher ratio in the light-eutrophic and suboxic layers than their counterparts. The advantageous active AOB were numerically predominated by the Nitrosomonas cluster in the suboxic layers, and the Nitrosospira cluster in the anoxic layers, respectively, both of which were distributed in diverse frequencies in different eutrophication statuses. The role and community composition diversities of active ammonia oxidizers in freshwater sediments were attributed to the different eutrophication (including nitrogen and organic carbon content) and oxygen statuses.     

Free radical production by the red tide alga, Chattonella antiqua.

Summary The red tide alga,Chattonella antiqua, was found to show a strong chemiluminescence, using luminol as the reagent, when exposed to ultraviolet irradiation. This luminescence was completely inhibited by ascorbate or catalase, suggesting that hydrogen peroxide was generated by the plankton. Red tide cells exposed to fish gill mucus from young yellowtail resulted in the release of a large number of mucocysts and a weak luminosity, and showed a strong reduction of cytochromec in the medium. Therefore, the discharge of mucocysts from the red tide, induced by the presence of gill mucus, may be accompanied by the release of active oxygen species. The active oxygen may be involved in depolymerization of mucus glycoproteins from the gill lamellae.     

Glycerophosphate-dependent hydrogen peroxide production by brown adipose tissue mitochondria and its activation by ferricyanide

Oxidation of glycerophosphate (GP) by brown adipose tissue mitochondria in the presence of antimycin A was found to be accompanied by significant production of hydrogen peroxide. GP-dependent hydrogen peroxide production could be detected by p-hydroxyphenylacetate fluorescence changes or as an antimycin A-insensitive oxygen consumption. One-electron acceptor, potassium ferricyanide, highly stimulated the rate of GP-dependent antimycin A-insensitive oxygen uptake, which was prevented by inhibitors of mitochondrial GP dehydrogenase (mGPDH) or by coenzyme Q(CoQ). GP-dependent ferricyanide-induced peroxide production was also determined luminometrically, using mitochondria or partially purified mGPDH. Ferricyanide-induced peroxide production was negligible, when succinate or NADH was used as a substrate. These results indicate that hydrogen peroxide is produced directly by mGPDH and reflect the differences in the transport of reducing equivalents from mGPDH and succinate dehydrogenase to the CoQ pool. The data suggest that more intensive production of reactive oxygen species may be present in mammalian cells with active mGPDH.     

Effect of aeration on denitrification byOchrobactrum anthropi SY509

Aeration was found to affect the biological denitrification byOchrobactrum anthropi SY509. Although cell growth was vigorous under 1 vvm of aeration and an agitation speed of 400 rpm in a 3-L jar fermentor, almost no nitrate was removed. Yet under low agitation speeds (100, 200, and 300 rpm), denitrification occurred when the dissolved oxygen was exhausted shortly after the inoculation of the microorganism.Ochrobactrum anthropi SY509 was found to express highly active denitrifying enzymes under anaerobic conditions. The microorganism also synthesized denitrifying enzymes under aerobic conditions (1 vvm and 400 rpm), yet their activity was only 60% of the maximum level under anaerobic conditions and the nitrate removal efficiency was merely 15%. However, although the activities of the denitrifying enzymes were inhibited in the presence of oxygen, they were fully recovered when the conditions were switched to anaerobic conditions.     

大气增温对杉木幼树叶片及细根生理特征的影响

为揭示亚热带森林对未来全球变暖的生理响应特征,本研究以杉木为研究对象,利用开顶式增温方式模拟气候变暖,研究其对叶片和细根丙二醛含量、活性氧代谢、渗透调节物质含量以及抗氧化酶活性的影响。研究结果显示：（1）增温显著增加杉木叶片和细根的丙二醛含量,且叶片丙二醛含量显著高于细根,说明增温加剧了杉木叶片和细根氧化损伤,且叶片氧化损伤程度高于细根;（2）增温后,杉木叶片脯氨酸和可溶性蛋白含量降低,细根脯氨酸和可溶性蛋白含量则增加;（3）增温显著提高了杉木叶片过氧化物酶活性,对杉木细根抗氧化酶活性无显著影响;（4）增温后,杉木叶片和细根活性氧含量未发生显著变化,杉木叶片活性氧含量显著高于细根。综合分析表明,尽管增温增加了杉木叶片和细根的氧化损伤,但杉木可以通过提高抗氧化保护酶活性（叶片）和积累较多的渗透调节物质（细根）来维持体内活性氧代谢平衡。可见,杉木地上和地下部分器官间的相互合作与协调使杉木能有效地适应高温环境。     

Mitochondrial function plasticity in <Emphasis Type="Italic">Acanthamoeba castellanii</Emphasis> during growth in batch culture

The alterations in mitochondrial bioenergetics during growth in a batch culture of Acanthamoeba castellanii were studied. The capacity of cytochrome pathway-dependent respiration measured in vitro decreased from the intermediary phase, when cell division slowed down. The pattern of the cytochrome pathway capacity changes was paralleled from the intermediary phase by alterations in the amount of total (and reducible) membranous ubiquinone. These changes were accompanied by a decrease in mitochondrial reactive oxygen species production in vitro (when no energy-dissipating system was active), and almost no change in superoxide dismutase activity and protein level, thus indicating an equivalent need for this enzyme in oxidative stress defence in A. castellanii culture. On the other hand, a decrease in the activity and protein level of alternative oxidase and uncoupling protein was observed in vitro, when cells shifted from the exponential growth phase to the stationary phase. It turned out that the contribution of both energy-dissipating systems in the prevention of mitochondrial reactive oxygen species generation in vivo could lead to its constant level throughout the growth cycle of A. castellanii batch culture. Hence, the observed functional plasticity insures survival of high quality cysts of A. castellanii cells.     

EFFECT OF HYPEROXIA ON THE GROWTH AND PHOTOSYNTHESIS OF POLAR SEA ICE MICROALGAE1

Sea ice algal communities are naturally exposed to very high concentrations of dissolved oxygen, which are likely to lead to increasing stress levels and declines in productivity. To test this hypothesis, cultures of Fragilariopsis cylindrus (Grun?) Hasle, Pseudo‐nitzschia sp., Fragilariopsis curta (Van Heurch), Porosira glacialis (Grunow), and Entomoneis kjellmannii (Cleve) from Antarctic sea ice and Nitzschia frigida from Arctic sea ice were exposed to elevated dissolved oxygen levels, and their growth, maximum quantum yield, relative maximum electron transport rate, and photosynthetic efficiency were measured. At oxygen concentrations equivalent to approximately four times air saturation (89% oxygen), the growth rate and maximum quantum yield were significantly reduced in all taxa. When the oxygen concentration was regularly allowed to drop, the effect on growth and quantum yield was reduced. At lower dissolved oxygen concentrations (52%), the declines in growth and quantum yield were reduced but were still mostly significantly different from the controls (21% oxygen). It is likely that the generation of excess active oxygen radicals in the presence of free oxygen is responsible for most of the decline in growth, maximum quantum yield, relative maximum electron transport rate, and photosynthetic efficiency in all species.     

Flash oxygen yield patterns of autotrophically and photoheterotrophically grown Chlamydobotrys stellata in the presence and absence of lipophilic acceptors

The obligate phototrophic green alga Chlamydobotrys stellata does not evolve oxygen when grown in CO₂-free atmosphere on acetate. With the application of the lipophilic acceptor 2,6-dichloro-p-benzoquinone it was investigated whether this phenomenon is caused by the inactivation of the water-splitting system or by an inhibition of the electron transport chain. It was found that in the presence of DCQ, the photoheterotrophic alga exhibited a normal period-4 flash oxygen pattern, but the steady state yield was only 25% of that measured in the autotrophic cells. After DCQ addition, the initial distribution of S-states and the values of the transition probabilities proved to be the same in the autotrophic and photoheterotrophic algae. These results indicate that photoheterotrophic growth conditions inhibit the electron transport of Chl. stellata behind the acceptor site of DCQ, but the water-splitting system remains active with a reduced oxygen evolving capacity.Abbreviations Chl chlorophyll - DCQ 2,6-dichloro-p-benzoquinone - DCMU 3-(3,4)-dichlorophenyl)-1,1-dimethylurea - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - pBQ 1,4-benzoquinone - PS I photosystem I - PS II photosystem II     

Effects of oxygen and chloramphenicol on Frankia nitrogenase activity

The kinetics of asymbiotic nitrogenase activity in three strains of the actinomycete Frankia were studied. Decay rates for enzyme activity were determined by adding chloramphenicol to active acetylene-reducing cells and measuring the time required for all activity to cease. Synthesis rates were measured by bubbling oxygen through actively-reducing cells (which totally destroyed all activity) and then measuring the time required for activity to return to normal. Decay rates (t _1/2) for these three strains were approximately 30 to 40 min. Synthesis rates were slower and initial nitrogenase activities were recorded about 110 min (DDB 011610) or 210 min (DDB 020210 and WgCc1.17) after return to air-equilibrated cultures. Frankia strain WgCc1.17 showed a greater sensitivity to oxygen and nitrogenase activity was totally lost when cells were bubbled only with atmospheric concentrations of oxygen. The results presented here indicate that nitrogenase activity turnover time is relatively rapid, on the order of minutes rather than hours or days. However, regulation of nitrogenase activity will differ from one strain to another and asmmbiotic characterization will be useful for understanding nitrogenase regulation in the bacterial-plant symbiosis.Contribution no. 879 from the Battelle-Kettering Laboratory     

Mechanism of Catechin Chemiluminescence in the Presence of Active Oxygen

The photon emission (chemiluminescence; CL) of catechin in the presence of active oxygen species (hydrogen peroxide, hydroxyl radical tert-butyl hydroperoxide and tert-butyl oxyl radical) and acetaldehyde was confirmed to occur non-enzymatically at room temperature in aqueous neutral conditions. The CL intensity [P] in the presence of active oxygen species (X), catalytic species (Y) and receptors (Z) is predicted by [P] = k [X] [Y] [Z]. The calculated photon constants (k) of 8 catechins and gallic acid were 8.23 × 10⁶ M⁻² s⁻¹ counts ((−)-epigallocatechin), 2.78 × 10⁶ ((−)-epigallocatechin gallate), 4.66 × 10⁵ ((−)-gallocatechin gallate), 4.36 × 10⁵ ((−)-gallocatechin), 2.70 × 10⁵ ((−)-epicatechin), 6.44 × 10⁴ ((−)-catechin), 5.85 × 10⁴ ((−)-epicatechin gallate), 4.78 × 10⁴ (gallic acid) and 3.54 × 10⁴ ((−)-catechin gallate), respectively. The system of active oxygen species, catalytic species and receptors is proposed to be a scavenging mechanism for active oxygen species. In the presence of acetaldehyde, (−)-epigallocatechin (maximum k value among catechins tested) reacted with tert-BuOOH to form tert-BuOH as determined by HPLC analysis.