Anaerobic microbial communities and their potential for bioenergy production in heavily biodegraded petroleum reservoirs

Most of the oil in low temperature, non-uplifted reservoirs is biodegraded due to millions of years of microbial activity, including via methanogenesis from crude oil. To evaluate stimulating additional methanogenesis in already heavily biodegraded oil reservoirs, oil sands samples were amended with nutrients and electron acceptors, but oil sands bitumen was the only organic substrate. Methane production was monitored for over 3000 days. Methanogenesis was observed in duplicate microcosms that were unamended, amended with sulfate or that were initially oxic, however methanogenesis was not observed in nitrate-amended controls. The highest rate of methane production was 0.15 μmol CH₄ g⁻¹ oil d⁻¹, orders of magnitude lower than other reports of methanogenesis from lighter crude oils. Methanogenic Archaea and several potential syntrophic bacterial partners were detected following the incubations. GC–MS and FTICR–MS revealed no significant bitumen alteration for any specific compound or compound class, suggesting that the very slow methanogenesis observed was coupled to bitumen biodegradation in an unspecific manner. After 3000 days, methanogenic communities were amended with benzoate resulting in methanogenesis rates that were 110-fold greater. This suggests that oil-to-methane conversion is limited by the recalcitrant nature of oil sands bitumen, not the microbial communities resident in heavy oil reservoirs.     

Evidence for diet partitioning among three coexisting native freshwater fishes in South Africa's Cape Fold Ecoregion

The partitioning of limited resources commonly explains how different species can coexist within the same ecological community. In this 2010 study, the diets of three coexisting freshwater fishes (Cape galaxias Galaxias zebratus, n = 27; Cape kurper Sandelia capensis, n = 60; Breede River redfin Pseudobarbus burchelli, n = 77) were characterised and compared in three headwater streams in South Africa's Cape Fold Ecoregion using gut contents and stable isotope analyses. These data were analysed to ascertain whether the three species exploit distinct trophic niches. Both approaches provided evidence that these species occupy different trophic niches, though with some overlap. However, dietary differences among sites were not consistent and were probably influenced by site-specific factors like resource availability. Pseudobarbus burchelli had a broader niche breadth at Tierkloof Stream than the other two species, but not at Waaihoek or Tierstel Streams. Our results also suggest that P. burchelli consumed a more omnivorous diet than do the other two species, whereas S. capensis occupied a higher trophic position than the other two species and consumed vertebrates. Our findings suggest that these species occupy non-equivalent feeding niches in Cape Fold Ecoregion headwater streams, and that diet partitioning might facilitate their coexistence in these systems.     

Physiological adaptations of an under-ice population of Pseudocalanus in Barrow Strait (N.W.T) to increasing food supply in spring

Summary Zooplankton and water samples were collected at weekly intervals between April 25 and May 30, 1986 in Barrow Strait, N.W.T. (Canadian Arctic Archipelago). In tows from 0–30 m, the zooplankton community (>202 m) was dominated by Pseudocalanus. The population was apparently growing and developing as shown by an increase in the proportion of adults (stage VI) and decreases in the proportion of stages III, IV, and V as the season progressed. Respiration and excretion rates of the Pseudocalanus populations were probably linked, there being an immediate increase in excretion rate, accompanying an increase in feeding rate when chlorophyll concentrations increased, which was followed by a smaller increase in respiration rate after a time lag. Hence, there was a large decrease in the ON ratio. Increased metabolism coincided with changes in the population structure, as did protease and bodily protein, but could not be clearly linked to dietary acclimation. Only laminarinase activity could be statistically related to an identifiable fraction of potential nutritional value in the water, particulate soluble carbohydrate, but neither showed overall seasonal change.     

应用气-质联用仪测定三种螺旋藻中的甾醇成分

应用GLC/MS联用仪对室内培养的钝顶螺旋藻(Spirulina platensis (Nordstedt) Geitler)、极大螺旋藻(S.maxima (Stechell & Gardiner) Geitler)和盐泽螺旋藻(S.subsalsa Oerst)的甾醇成分进行了测定。从钝顶螺旋藻和盐泽螺旋藻中共分出11个相同的甾醇组分:胆甾醇、胆甾烷醇、芸苔甾醇、麦角甾醇、海绵甾醇、菜子甾醇、豆甾醇、24-乙基-Δ~(5,7,22)-胆甾醇、β-谷甾醇、异岩藻甾醇和4α,23,24-三甲基Δ~(5,22)-胆甾醇;从极大螺旋藻中只分离出8个甾醇组分。其中胆甾醇含量最高。4α,23,24-三甲基-Δ~(5,22)-胆甾醇为蓝藻中首次报导。     

Branched fibers in dystrophic mdx muscle are associated with a loss of force following lengthening contractions

We demonstrated that the susceptibility of skeletal muscle to injury from lengthening contractions in the dystrophin-deficient mdx mouse is directly linked with the extent of fiber branching within the muscles and that both parameters increase as the mdx animal ages. We subjected isolated extensor digitorum longus muscles to a lengthening contraction protocol of 15% strain and measured the resulting drop in force production (force deficit). We also examined the morphology of individual muscle fibers. In mdx mice 1–2 mo of age, 17% of muscle fibers were branched, and the force deficit of 7% was not significantly different from that of age-matched littermate controls. In mdx mice 6–7 mo of age, 89% of muscle fibers were branched, and the force deficit of 58% was significantly higher than the 25% force deficit of age-matched littermate controls. These data demonstrated an association between the extent of branching and the greater vulnerability to contraction-induced injury in the older fast-twitch dystrophic muscle. Our findings demonstrate that fiber branching may play a role in the pathogenesis of muscular dystrophy in mdx mice, and this could affect the interpretation of previous studies involving lengthening contractions in this animal. skeletal muscle; mdx mouse; lengthening contraction; Duchenne muscular dystrophy     

The association between sociodemographic,hormonal, tubo-ovarian factors and bacterial count in Chlamydia and Mycoplasma infections with infertility

Aim: To determine if there is an association between the Chlamydia and Mycoplasma infections with socio-demographic and clinical factors, and also with infertility. Methods: We conducted a study on 100 infertile married women and 100 control group, and collected data on the socio-demographic, hormonal and tubo-ovarian factors. The results of the endocervical swabs were analyzed for Mycoplasma and Chlamydia infection, the bacterial counts were also determined. Results: The percentage positivity to infection was significantly more among the infertile group compared to the control group, and also significantly more among the age group <30 years old. The positivity for infection with Chlamydia and/or Mycoplasma was significantly correlated with age, history of irregular menstruation, and history of previous abortion. Further sub-analysis of the infertile group showed that positivity to Chlamydia and/or Mycoplasma infection was significantly correlated to hormonal factors, ovarian factors, irregular menstruation, and previous abortion. Regression analysis showed that hormonal, ovarian factors, and irregular menstruation were the most significant factors in the positivity to Chlamydia and Mycoplasma infection. Bacterial count was significantly correlated with age, history of irregular menstruation, and history of previous abortion. Conclusion: Infection to Chlamydia and Mycoplasma is associated to younger age (?30 years old), and occurs in the infertile women. There is an interplay between infection in younger women, irregular menstruation, hormonal, and tubo-ovarian factors with infertility. Bacterial count was significantly correlated with age, history of irregular menstruation, and history of previous abortion.     

Sediment cooling triggers germination and sulfate reduction by heat-resistant thermophilic spore-forming bacteria

Thermophilic endospores are widespread in cold marine sediments where the temperature is too low to support growth and activity of thermophiles in situ. These endospores are likely expelled from warm subsurface environments and subsequently dispersed by ocean currents. The endospore upper temperature limit for survival is 140°C, which can be tolerated in repeated short exposures, potentially enabling transit through hot crustal fluids. Longer-term thermal tolerance of endospores, and how long they could persist in an environment hotter than their maximum growth temperature, is less understood. To test whether thermophilic endospores can survive prolonged exposure to high temperatures, sediments were incubated at 80–90°C for 6, 12 or 463 days. Sediments were then cooled by 10–40°C, mimicking the cooling in subsurface oil reservoirs subjected to seawater injection. Cooling the sediments induced sulfate reduction, coinciding with an enrichment of endospore-forming Clostridia. Different Desulfofundulus, Desulfohalotomaculum, Desulfallas, Desulfotomaculum and Desulfofarcimen demonstrated different thermal tolerances, with some Desulfofundulus strains surviving for >1 year at 80°C. In an oil reservoir context, heat-resistant endospore-forming sulfate-reducing bacteria have a survival advantage if they are introduced to, or are resident in, an oil reservoir normally too hot for germination and growth, explaining observations of reservoir souring following cold seawater injection.     

Breaking barriers? Ethnicity and socioeconomic background impact on early career progression in the fields of ecology and evolution

The academic disciplines of Science, Technology, Engineering and Mathematics (STEM) have long suffered from a lack of diversity. While in recent years there has been some progress in addressing the underrepresentation of women in STEM subjects, other characteristics that have the potential to impact on equality of opportunity have received less attention. In this study, we surveyed 188 early career scientists (ECRs), defined as within 10 years of completing their PhD, in the fields of ecology, evolutionary biology, behaviour, and related disciplines. We examined associations between ethnicity, age, sexual orientation, sex, socioeconomic background, and disability, with measures of career progression, namely publication record, number of applications made before obtaining a postdoc, type of contract, and number of grant applications made. We also queried respondents on perceived barriers to progression and potential ways of overcoming them. Our key finding was that socioeconomic background and ethnicity were associated with measures of career progression. While there was no difference in the number of reported first‐authored papers on PhD completion, ethnic minority respondents reported fewer other‐authored papers. In addition, ECRs from a lower socioeconomic background were more likely to report being in teaching and research positions, rather than research‐only positions, the latter being perceived as more prestigious by some institutions. We discuss our findings in the context of possible inequality of opportunity. We hope that this study will stimulate wider discussion and help to inform strategies to address the underrepresentation of minority groups in the fields of ecology and evolution, and STEM subjects more widely.