A 70-day experiment was performed with Daphnia magna exposed to waterborne Am-241 on a range of concentrations (from 0.4 to 40 Bq ml-1) in order to test chronic effects of internal alpha irradiation on respiration, somatic growth and reproduction over three successive generations. Changes in Am-241 concentrations were followed in the water and in daphnid tissues, eggs and cuticles. Corresponding average dose rates of 0.3, 1.5 and 15 mGy h-1 were estimated. This study confirmed that oxygen consumption increased significantly in the first generation (F0) after 6 days of exposure to a dose rate ≥1.5 mGy h-1. Consequences were limited to a reduction in body length (5%) and dry mass of females (16%) and eggs (8%) after 23 days of exposure, while mortality and fecundity remained unaffected. New cohorts were started with neonates of broods 1 and 5, to examine potential consequences of the reduced mass of offspring for subsequent exposed generations. Results strongly contrasted with those observed in F0. At the highest dose rate, an early mortality of 38-90% affected juveniles while survivors showed delayed reproduction and reduced fecundity in F1 and F2. At 0.3 and 1.5 mGy h-1, mortality ranged from 31 to 38% of daphnids depending on dose rate, but was observed only in generation F1 started with neonates of the brood 1. Reproduction was affected through a reduction in the proportion of breeding females, occurring in the first offspring generation at 1.5 mGy h-1 (to 62% of total daphnids) and in the second generation at 0.3 mGy h-1 (to 69% of total daphnids). Oxygen consumption remained significantly higher at dose rates ≥0.3 mGy h-1 than in the control in almost every generation. Body size and mass continued decreasing in relation to dose rate, with a significant reduction in mass ranging from 15% at 0.3 mGy h-1 to 27% at 15 mGy h-1 in the second offspring generation. © 2008 Elsevier B.V. All rights reserved.

Many biological seep studies focused on the distribution, structure, nutrition and food web architecture of seep communities as well as on their interaction with the seep geochemistry. However, overall respiration at cold seeps received only little attention. We conducted in-situ oxygen flux measurements in combination with ex-situ oxygen micro-profiles, respiration measurements, as well as rate determinations of microbial methane and sulfate turnover to assess respiration pathways as well as carbon turnover at a seep habitat that was recently discovered alongside the Hikurangi Margin offshore northern New Zealand. This habitat is dominated by dense beds of tube-building, heterotrophic ampharetid polychaetes. Average total oxygen uptake (TOU) from this habitat was very high (83.7 mmol m- 2 day- 1). TOU at a non-seep reference site ranged between 2.7 and 5.8 mmol m- 2 day- 1. About 37% (30.8 mmol m- 2 day- 1) of the average TOU was consumed by ampharetids. Considering mean diffusive oxygen uptake (8.5 mmol m- 2 day- 1) the remaining fraction of ~ 53% of the TOU (44.4 mmol m- 2 day- 1) might be explained by respiration of epibenthic organisms as well as aerobic methane and sulfide oxidation at the sediment-water interface. The strongly negative carbon isotopic signatures (- 52.9 ± 5‰ VPDB) of the ampharetid tissues indicate a methane derived diet. However, carbon production via anaerobic oxidation of methane (AOM) was too low (0.1 mmol C m- 2 day- 1) to cover the mean carbon demand of the ampharetid communities (21 mmol C m- 2 day- 1). Likely, organic carbon generated via aerobic methane oxidation represents their major carbon source. This is in contrast to other seep habitats, where energy bound in methane is partly transferred to sulfide via AOM and finally consumed by sulfide-oxidizing chemoautotrophs providing carbon that subsequently enters the benthic food web. © 2009 Elsevier B.V. All rights reserved.

1. The specific respiration rate of 13 chironomid taxa and Chaoborus were measured to test the hypothesis of the relation between a species' ability to regulate their oxygen uptake and their distributional patterns among nine study lakes in British Columbia, Canada. 2. Respiration patterns of individual taxa were modelled using piecewise linear regression with break point and simple hyperbolic functions. Three types of respiration curves were identified: (i) classical oxy-conformers (e.g. littoral Cricotopus) which cannot sustain a sufficient oxygen uptake with decreasing oxygen availability; (ii) oxy-regulators (e.g. profundal Chironomus) which can regulate and maintain a constant respiration until a certain critical point and (iii) oxy-stressors (Micropsectra) which increase their respiration rate with decreasing oxygen availability until a critical point. 3. Respiration was measured at two different temperatures (10 and 20°C), and over the range of oxygen saturation conditions studied here (0-90%) mean Q10 values varied from 1.3 to 2.5. 4. The results show that different chironomid taxa have varying sensitivity to low oxygen concentrations and different respiratory responses to increased temperature. The critical point increased to higher oxygen saturation for six taxa, decreased for one taxon and was unchanged for two taxa. 5. The results illustrate one of the possible biological mechanisms behind the use of chironomids as temperature and climate indicators in palaeoecological studies by exploring the link between temperature and respiration physiology. © 2007 The Authors.

Photosynthetically produced hydrogen is an attractive, sustainable fuel. Semiartificial in vitro techniques have been successfully implemented in which hydrogenases were attached to isolated photosystems for hydrogen production. However, in vitro systems are in general short lived as metabolic processes that support self-repair and maintenance are missing. So far, photosystem–hydrogenase fusions have been tested in vitro only. Here, we report photosynthetic hydrogen production using a photosystem I–hydrogenase fusion in vivo. The NiFe-hydrogenase HoxYH of the cyanobacterium Synechocstis sp. PCC 6803 was fused to its photosystem I subunit PsaD in close proximity to the 4Fe4S cluster FB, which ordinarily donates electrons to ferredoxin. The resultant psaD-hoxYH mutant grows photoautotrophically, achieves a high concentration of photosynthetically produced hydrogen of 500 μM under anaerobic conditions in the light and does not take up the generated hydrogen. Our data indicate that photosynthetic hydrogen production in psaD-hoxYH is most likely based on both oxygenic and anoxygenic photosynthesis.

Harnessing nitrous oxide (N2O)-reducing bacteria is a promising strategy to reduce the N2O footprint of engineered systems. Applying a preferred organic carbon source as an electron donor accelerates N2O consumption by these bacteria. However, their N2O consumption potential and activity when fed different organic carbon species remain unclear. Here, we systematically compared the effects of various organic carbon sources on the activity of N2O-reducing bacteria via investigation of their biokinetic properties and genomic potentials. Five organic carbon sources—acetate, succinate, glycerol, ethanol, and methanol—were fed to four N2O-reducing bacteria harboring either clade I or clade II nosZ gene. Respirometric analyses were performed with four N2O-reducing bacterial strains, identifying distinct shifts in DO- and N2O-consumption biokinetics in response to the different feeding schemes. Regardless of the N2O-reducing bacteria, higher N2O consumption rates, accompanied by higher biomass yields, were obtained with acetate and succinate. The biomass yield (15.45 ± 1.07 mg-biomass mmol-N2O−1) of Azospira sp. strain I13 (clade II nosZ) observed under acetate-fed condition was significantly higher than those of Paracoccus denitrificans and Pseudomonas stutzeri, exhibiting greater metabolic efficiency. However, the spectrum of the organic carbon species utilizable to Azospira sp. strain I13 was limited, as demonstrated by the highly variable N2O consumption rates observed with different substrates. The potential to metabolize the supplemented carbon sources was investigated by genomic analysis, the results of which corroborated the N2O consumption biokinetics results. Moreover, electron donor selection had a substantial impact on how N2O consumption activities were recovered after oxygen exposure. Collectively, our findings highlight the importance of choosing appropriate electron donor additives for increasing the N2O sink capability of biological nitrogen removal systems.

Background: Sirtuin 6 (SIRT6) is a NAD +-dependent deacetylase with key roles in cell metabolism. High SIRT6 expression is associated with adverse prognosis in breast cancer (BC) patients. However, the mechanisms through which SIRT6 exerts its pro-oncogenic effects in BC remain unclear. Here, we sought to define the role of SIRT6 in BC cell metabolism and in mouse polyoma middle T antigen (PyMT)-driven mammary tumors.