Biodegradation of Petroleum Hydrocarbons in Seawater at Low Temperatures (0–5 °C) and Bacterial Communities Associated with Degradation

In this study biodegradation of hydrocarbons in thin oil films was investigated in seawater at low temperatures, 0 and 5 °C. Heterotrophic (HM) or oil-degrading (ODM) microorganisms enriched at the two temperatures showed 16S rRNA sequence similarities to several bacteria of Arctic or Antarctic origin. Biodegradation experiments were conducted with a crude mineral oil immobilized as thin films on hydrophobic Fluortex adsorbents in nutrient-enriched or sterile seawater. Chemical and respirometric analysis of hydrocarbon depletion showed that naphthalene and other small aromatic hydrocarbons (HCs) were primarily biodegraded after dissolution to the water phase, while biodegradation of larger polyaromatic hydrocarbons (PAH) and C₁₀–C₃₆ n-alkanes, including n-hexadecane, was associated primarily with the oil films. Biodegradation of PAH and n-alkanes was significant at both 0 and 5°C, but was decreased for several compounds at the lower temperature. n-Hexadecane biodegradation at the two temperatures was comparable at the end of the experiments, but was delayed at 0°C. Investigations of bacterial communities in seawater and on adsorbents by PCR amplification of 16S rRNA gene fragments and DGGE analysis indicated that predominant bacteria in the seawater gradually adhered to the oil-coated adsorbents during biodegradation at both temperatures. Sequence analysis of most DGGE bands aligned to members of the phyla Proteobacteria (Gammaproteobacteria) or Bacteroidetes. Most sequences from experiments at 0°C revealed affiliations to members of Arctic or Antarctic consortia, while no such homology was detected for sequences from degradation experiment run at 5°C. In conclusion, marine microbial communities from cold seawater have potentials for oil film HC degradation at temperatures ≤5°C, and psychrotrophic or psychrophilic bacteria may play an important role during oil HC biodegradation in seawater close to freezing point.     

Influence of substratum on the degradation processes in diesel polluted sub-Antarctic soils (Crozet Archipelago)

Biodegradation by naturally occurring populations of microorganisms is a major mechanism for the removal of oil hydrocarbons from the environment. Therefore, follow-up of bacterial populations and chemical indices of biodegradation are important components of contaminated site assessment studies. Over a 4-year period following an accidental diesel contamination of the sub-Antarctic Crozet Archipelago (51°51′E–46°25′S), a field study was carried out in the contaminated area that is located in a transition zone between an arid fell-field (upstream) and a wet vegetated area (downstream). This study included a monitoring of heterotrophic and hydrocarbon-degrading bacterial abundance and chemical analysis of the remaining hydrocarbons. Significant higher number of heterotrophic and hydrocarbon-degrading bacterial counts revealed a rapid acclimation of sub-Antarctic microbial soil communities to the diesel fuel contamination. A chemical survey conducted during the last 2 years (2002 and 2003) showed that the total extractable hydrocarbons (TPH) content in arid fell field was reduced to ≤50% of their value while it was reduced only to ≤65% in vegetated soil. In addition, the decrease of TPH was always higher in the presence of fertilizer in the arid contaminated area, while fertilizer addition was almost inefficient in the wet contaminated one. All these results demonstrate a serious influence of the soil properties on the degradation rate. However, all chemical indices showed a significant reduction of alkanes and light aromatics in both contaminated area confirming a regular oil degradation process.     

Development of a standard bacterial consortium for laboratory efficacy testing of commercial freshwater oil spill bioremediation agents

Six crude oil-degrading bacterial strains isolated from different soil and water environments were combined to create a defined consortium for use in standardized efficacy testing of commercial oil spill bioremediation agents (OSBA). The isolates were cryopreserved in individual aliquots at pre-determined cell densities, stored at −70°C, and thawed for use as standardized inocula as needed. Aliquots were prepared with precision (typically within 10% of the mean) ensuring reproducible inoculation. Five of the six strains displayed no appreciable loss of viability during cryopreservation exceeding 2.5 years, and five isolates demonstrated stable hydrocarbon-degrading phenotypes during inoculum preparation and storage. When resuscitated, the defined consortium reproducibly biodegraded Alberta Sweet Mixed Blend crude oil (typically ± 7% of the mean of triplicate cultures), as determined by quantitative gas chromatography–mass spectrometry of various analyte classes. Reproducible biodegradation was observed within a batch of inoculum in trials spanning 2.5 years, and among three batches of inoculum prepared more than 2 years apart. Biodegradation was comparable after incubation for 28 days at 10°C or 14 days at 22°C, illustrating the temperature tolerance of the bacterial consortium. The results support the use of the synthetic consortium as a reproducible, predictable inoculum to achieve standardized efficacy tests for evaluating commercial OSBA. Received 31 August 1998/ Accepted in revised form 30 November 1998     

Adaptive latitudinal variation of the duration and thermal requirements for development in the ground beetle Amara communis (Panz.) (Coleoptera, Carabidae)

The data are obtained on development time at six constant temperatures (12, 14, 16, 18, 20, 22°C) and thermal requirements for preimaginal development in a ground beetle Amara communis from Arkhangelsk (64°34′N) and St. Petersburg (59°53′N). The larval and pupal development times were found to be significantly shorter in the Arkhangelsk than in the St. Petersburg population under all temperatures. As a result, total preimaginal development appeared to be shorter by 6.2–6.6% in the Arkhangelsk population. The regression lines of the larval, pupal and total (egg-to-adult) development rate on temperature for the Arkhangelsk population run above and steeper than the respective lines for the St. Petersburg population. Both populations share the similar values of the thermal thresholds (7.2–8.2°C). This explains faster preimaginal development in the northern population under all temperatures above the threshold. Thus, the slope of the regression lines increases, i.e., the sum of degree-days decreases, whereas the thermal threshold for development exhibited no distinctive changes from south to north in this species. Adults from Arkhangelsk reared in the experiments appeared heavier on the average in comparison with those from St. Petersburg, especially at 18–22°C. Temperature did not significantly affect adult weight, except the fact that the beetles were slightly heavier at 20 and 22°C. Consequently, the well-known “temperature-size rule” is violated in this species. Relative growth rate in larvae of A. communis increased considerably with temperature rise from 14 to 22°C. It was significantly higher in the beetles from Arkhangelsk at 18–22°C. There were no differences in larval growth rate between the two populations at 14 and 16°C.     

Degradation of RNA during the autolysis of Saccharomyces cerevisiae produces predominantly ribonucleotides

Autolytic degradation of yeast RNA occurs in many foods and beverages and can impact on the sensory quality of the product, but the resulting complex mixture of nucleotides, nucleosides and nucleobases has not been properly characterised. In this study, yeast autolysis was induced by incubating cell suspensions of Saccharomyces cerevisiae at 30–60 °C (pH 7.0), and at pH 4.0–7.0 (40 °C) for 10–14 days, and the RNA degradation products formed during the process were determined by reversed-phase HPLC. Up to 95% of cell RNA was degraded, with consequent leakage into the extracellular environment of mainly 3′-, 5′- and 2′-ribonucleotides, and lesser amounts of polynucleotides, ribonucleosides and nucleobases. The rate of RNA degradation and the composition of the breakdown products varied with temperature and pH. RNA degradation was fastest at 50 °C (pH 7.0). Autolysis at lower temperatures (30 °C and 40 °C) and at pH 5.0 and 6.0 favoured the formation of 3′-nucleotides, whereas autolysis at 40 °C and 50 °C (pH 7.0) favoured 5′- and 2′-nucleotides. The best conditions for the formation of the two flavour-enhancing nucleotides, 5′-AMP and 5′-GMP, were 50 °C (pH 7.0) and pH 4.0 (40 °C), respectively.     

Effectiveness of bioremediation for oil-polluted Antarctic seawater

The effectiveness of a specific fertiliser (INIPOL EAP 22) addition on bioremediation of oil-contaminated Antarctic coastal seawater was determined in the “Terre Adelie” area. Mesocosm studies were conducted to evaluate the effects of “Arabian light” crude oil contamination on coastal bacterioplanktonic communities. After oil addition, regular surveys of the bacterial changes of the oil-contaminated seawater were performed during 5-week periods during the austral summer of 1992/1993 and 1993/1994. All results (total, saprophytic and hydrocarbon-utilising bacterial abundance) clearly revealed a significant response of Antarctic bacterial communities to hydrocarbon contamination. A 1 order of magnitude increase of bacterial microflora occurred in seawater after crude oil contamination. A concomitant enrichment in oil-degrading bacteria was generally observed, from less than 0.001% of the community in uncontaminated samples to up to 50% after 3 weeks of contamination. Addition of fertiliser (INIPOL EAP 22) induced clear enhancement of both saprophytic and hydrocarbon-utilising microflora. Chemical analysis of the residual hydrocarbon fractions confirmed that fertiliser application increased the rate of oil biodegradation. Received: 27 March 1997 / Accepted: 20 October 1997     

Using Real-Time PCR to Assess Changes in the Hydrocarbon-Degrading Microbial Community in Antarctic Soil During Bioremediation

A real-time polymerase chain reaction (PCR) method to quantify the proportion of microorganisms containing alkane monooxygenase was developed and used to follow changes in the microbial community in hydrocarbon-contaminated Antarctic soil during a bioremediation field trial. Assays for the alkB and rpoB genes were validated and found to be both sensitive and reproducible (less than 2% intrarun variation and 25–38% interrun variation). Results from the real-time PCR analysis were compared to analysis of the microbial population by a culture-based technique [most probable number (MPN) counts]. Both types of analysis indicated that fertilizer addition to hydrocarbon-contaminated soil stimulated the indigenous bacterial population within 1 year. The proportion of alkB containing microorganisms was positively correlated to the concentration of n-alkanes in the soil. After the concentration of n-alkanes in the soil decreased, the proportion of alkane-degrading microorganisms decreased, but the proportion of total hydrocarbon-degrading microorganisms increased, indicating another shift in the microbial community structure and ongoing biodegradation.     

Environmental factors influencing the rate of hydrocarbon oxidation in temperate lakes.

Rates of hydrocarbon biodegradation were estimated by following oxygen uptake during mineral oil oxidation or oxidation of [1-14C]hexadecane to 14CO2, when these substrates were added to natural water samples from Wisconsin lakes. A lag phase preceded hydrocarbon oxidation, the length of which depended on population density or on factors influencing growth rate and on the presence of nonhydrocarbon organic compounds. Hydrocarbon oxidation was coincident with growth and presumably represented the development of indigenous hydrocarbon-degrading microorganisms in response to hydrocarbon additions. In detailed studies in Lake Mendota, it was found that, despite the continued presence of hydrocarbon-degrading microorganisms in water samples, seasonal variations in the rates of mineral oil and hexadecane oxidation occurred which correlated with seasonal changes in temperature and dissolved inorganic nitrogen and phosphorus. The temperature optimum for oil biodegradation remained at 20 to 25 C throughout the year, so that temperature was the main limiting factor during winter, spring, and fall. During summer, when temperatures were optimal, nutrient deficiencies limited oil biodegradation, and higher rates could be obtained by addition of nitrogen and phosphorus. The rates of hydrocarbon biodegradation were thus high only for about 1 month of the ice-free period, when temperature and nutrient supply were optimal. Nutrient limitation of oil biodegradation was also demonstrated in 25 nutrient-poor lakes of northern Wisconsin, although in almost every case oil-degrading bacteria were detected. Knowledge of temperature and nutrient limitations thus will help in predicting the fate of hydrocarbon pollutants in freshwater.     

Temperature impacts on anaerobic biotransformation of LNAPL and concurrent shifts in microbial community structure

Thermally-enhanced bioremediation is a promising treatment approach for petroleum contamination; however, studies examining temperature effects on anaerobic biodegradation in zones containing light non-aqueous phase liquids (LNAPLs) are lacking. Herein, laboratory microcosm studies were conducted for a former refinery to evaluate LNAPL transformation, sulfate reduction, and methane generation over a one-year period for temperatures ranging from 4 to 40 °C, and microbial community shifts were characterized. Temperatures of 22 and 30 °C significantly increased total biogas generation compared to lower (4 and 9 °C) and higher temperatures (35 and 40 °C; p < 0.1). Additionally, at 22 and 30 °C methane generation commenced ~6 months earlier than for 35 and 40 °C. Statistically significant biodegradation of benzene, toluene and xylenes was observed at elevated temperatures but not at lower temperatures (p < 0.1). Additionally, a novel differential chromatogram approach was developed to overcome challenges associated with resolving losses in complex mixtures of hydrocarbons, and application of this method revealed greater losses of hydrocarbons at 22 and 30 °C as compared to lower and higher temperatures. Finally, molecular biology assays revealed that the composition and activity of microbial communities shifted in a temperature-dependent manner. Collectively, results demonstrated that anaerobic biodegradation processes can be enhanced by increasing the temperature of LNAPL-containing soils, but biodegradation does not simply increase as temperature increases likely due to a lack of microorganisms that thrive at temperatures well above the historical high temperatures for a site. Rather, optimal degradation is achieved by holding soils at the high end of, or slightly higher than, their natural range.     

Environmental factors influencing the rate of hydrocarbon oxidation in temperate lakes.

Rates of hydrocarbon biodegradation were estimated by following oxygen uptake during mineral oil oxidation or oxidation of [1-14C]hexadecane to 14CO2, when these substrates were added to natural water samples from Wisconsin lakes. A lag phase preceded hydrocarbon oxidation, the length of which depended on population density or on factors influencing growth rate and on the presence of nonhydrocarbon organic compounds. Hydrocarbon oxidation was coincident with growth and presumably represented the development of indigenous hydrocarbon-degrading microorganisms in response to hydrocarbon additions. In detailed studies in Lake Mendota, it was found that, despite the continued presence of hydrocarbon-degrading microorganisms in water samples, seasonal variations in the rates of mineral oil and hexadecane oxidation occurred which correlated with seasonal changes in temperature and dissolved inorganic nitrogen and phosphorus. The temperature optimum for oil biodegradation remained at 20 to 25 C throughout the year, so that temperature was the main limiting factor during winter, spring, and fall. During summer, when temperatures were optimal, nutrient deficiencies limited oil biodegradation, and higher rates could be obtained by addition of nitrogen and phosphorus. The rates of hydrocarbon biodegradation were thus high only for about 1 month of the ice-free period, when temperature and nutrient supply were optimal. Nutrient limitation of oil biodegradation was also demonstrated in 25 nutrient-poor lakes of northern Wisconsin, although in almost every case oil-degrading bacteria were detected. Knowledge of temperature and nutrient limitations thus will help in predicting the fate of hydrocarbon pollutants in freshwater.     

Oil pollution in the North Sea—a microbiological point of view

In this study we determined oil degradation rates in the North Sea under most natural conditions. We used the heavy fuel oil, Bunker C, the major oil pollutant of the North Sea, as the model oil. Experiments were conducted in closed systems with water sampled during winter and repeated under identical conditions with water collected during summer. No nitrogen or phosphorous was added and conditions were chosen such that neither oxygen nor nutrients, present in the water, would become limiting during the experiments. We detected a fourfold increased degradation rate for water samples taken in summer (18°C water temperature) as compared to water sampled in winter (4°C water temperature). Under the assumption that biodegradation of oil can be regarded as a Michaelis-Menten type kinetic reaction, the kinectic constants V_max and K_M were determined for oil biodegradation at 4°C and 18°C. At both temperatures K_M was about 40 ppm, whereas V_max was 3–4 times higher at 18°C. From both V_max and the results of fermentation studies, we determined the maximum rates of Bunker C oil degradation in the North Sea as ∼20 g m⁻³a⁻¹ at 4°C in winter and 60–80 g m⁻³a⁻¹ at 18°C in summer. Furthermore, while over 25% of the oil was degraded within 6 weeks in summer, only 6.6% of the oil was degraded in winter. A higher incubation temperature in winter (18°C) increased both the rate and the percentage of oil degraded, but degradation did not reach the level obtained during the summer. While these data reflect the oxidation only of the hydrocarbons, we conducted experiments directly in the open sea to determine the contribution of abiotic factors to oil removal. Approximately 42% of the oil was lost within 6 weeks under these conditions in summer and 65% in winter. However, GC-MS analysis of the recovered oil showed no significant change in the alkane pattern that would indicate enhanced degradation. Thus, mainly abiotic factors such as erosion and dispersion rather than degradation were responsible for enhanced oil removal. Especially the high loss during winter can be attributed to frequent storms resulting in greater dispersion. In conclusion, the higher oil degrading potential of the microbial population in the North Sea was represented by a four times faster oil degradation during the summer. In-situ experiments showed that abiotic factors can have an equal (summer) or even higher (winter) impact on oil removal.     

Photosynthesis and lipid composition of the Antarctic endemic rhodophyte Palmaria decipiens: effects of changing light and temperature levels

In coastal waters, Antarctic rhodophytes are exposed to harsh environmental conditions throughout the year, like low water temperatures ranging from −1.8°C to 2°C and high light during the summer season. Photosynthetic performance under these conditions may be affected by slowed down enzymatic reactions and the increased generation of reactive oxygen species. The consequence might be a chronic photoinhibition of photosynthetic primary reactions related to increased fragmentation of the D1 reaction centre protein in photosystem II. It is hypothesized that changes in lipid composition of biomembranes may represent an adaptive trait to maintain D1 turnover in response to temperature variation. The interactive effects of high light and low temperature were studied on an endemic Antarctic red alga, Palmaria decipiens, sampled from two shore levels, intertidal and subtidal, and exposed to mesocosm experiments using two levels of natural solar radiation and two different temperature regimes (2–5°C and 5–10°C). During the experimental period of 23 days, maximum quantum yield of photosynthesis decreased in all treatments, with the intertidal specimens exposed at 5–10°C being most affected. On the pigment level, a decreasing ratio of phycobiliproteins to chlorophyll a was found in all treatments. A pronounced decrease in D1 protein concentration occurred in subtidal specimens exposed at 2–5°C. Marked changes in lipid composition, i.e. the ratio of saturated to unsaturated fatty acids, indicated an effective response of specimens to temperature change. Results provide new insights into mechanisms of stress adaptation in this key species of shallow Antarctic benthic communities.     

Early thermal history significantly affects the seasonal hyperplastic process occurring in the myotomal white muscle of <Emphasis Type="Italic">Dicentrarchus labrax</Emphasis> juveniles

The effect of early (embryonic and larval) thermal history on subsequent (juvenile) white muscle hyperplasia was studied in a teleost fish, the European sea bass (Dicentrarchus labrax L.). D. labrax, incubated and reared at constant temperatures of 13°C, 15°C or 20°C from the embryonic stage of half epiboly up to 18–19 mm in total length, were transferred to ambient seawater temperature and reared for the subsequent 14 months on commercial feed. The somatic growth of juveniles was linked to annual variations of ambient seawater temperature and inversely related to early rearing temperature, so that, after 14 months, the juveniles originally reared at low temperatures had compensated for the growth retardation experienced during early life. The white muscle growth process of juveniles was quantified after two periods of growth opportunity at ambient seawater temperature (100 and 400 days post-transfer) as well as, in order to follow total-length-dependent effects of early temperature and to discriminate total-length-independent effects of early temperature, on juveniles from the three batches sampled at six successive equivalent total lengths (31–33, 84–88, 141–145, 166–172, 196–206 and 211–220 mm). Our data demonstrate the existence of a seasonal recruitment of new white muscle fibres when seawater temperature increases and of a shrinkage of the largest white muscle fibres during the winter months. The seasonal recruitment of new white muscle fibres occurring in juveniles is linked to their early rearing temperature. Juveniles originating from low temperatures have a higher and longer capacity to recruit new white muscle fibres when seawater temperature increases, supporting their better somatic growth. This finding is discussed in relation to the early (embryonic and larval) myogenic processes of the three populations and is related to their sex ratio. This work was financed by the European Commission, FAIR Program no. PL96–1941 “Muscle Ontogeny in Sea bass and Trout”.     

Biodegradation of <Emphasis Type="Italic">n</Emphasis>-alkanes on oil–seawater interfaces at different temperatures and microbial communities associated with the degradation

Oil biodegradation studies have mainly focused on microbial processes in dispersions, not specifically on the interfaces between the oil and the seawater in the dispersions. In this study, a hydrophobic adsorbent system, consisting of Fluortex fabrics, was used to investigate biodegradation of n-alkanes and microbial communities on oil–seawater interfaces in natural non-amended seawater. The study was performed over a temperature range from 0 to 20 °C, to determine how temperature affected biodegradation at the oil–seawater interfaces. Biodegradation of n-alkanes were influenced both by seawater temperature and chain-length. Biotransformation rates of n-alkanes decreased by reduced seawater temperature. Low rate coefficients at a seawater temperature of 0 °C were probably associated with changes in physical–chemical properties of alkanes. The primary bacterial colonization of the interfaces was predominated by the family Oceanospirillaceae at all temperatures, demonstrating the wide temperature range of these hydrocarbonoclastic bacteria. The mesophilic genus Oleibacter was predominant at the seawater temperature of 20 °C, and the psychrophilic genus Oleispira at 5 and 0 °C. Upon completion of n-alkane biotransformation, other oil-degrading and heterotrophic bacteria became abundant, including Piscirickettsiaceae (Cycloclasticus), Colwelliaceae (Colwellia), Altermonadaceae (Altermonas), and Rhodobacteraceae. This is one of a few studies that describe the biodegradation of oil, and the microbial communities associated with the degradation, directly at the oil–seawater interfaces over a large temperature interval.     

Biodegradation kinetics of trans-4-methyl-1-cyclohexane carboxylic acid

Naphthenic acids are a complex mixture of organic compounds which naturally occur in crude oil. Low molecular weight components of the naphthenic acids are known to be toxic in aquatic environments and there is a need to better understand the factors controlling the kinetics of their biodegradation. In this study, a relatively low molecular weight naphthenic acid compound (trans-isomer of 4-methyl-1-cyclohexane carboxylic acid) and a microbial culture developed in our laboratory were used to study the biodegradation of this naphthenic acid and to evaluate the kinetics of the process in batch cultures. The initial concentration of trans-4-methyl-1-cyclohexane carboxylic acid (50–750 mg l⁻¹) did not affect the maximum specific growth rate of the bacteria at 23°C (0.52 day⁻¹) to the maximum biodegradable concentration (750 mg l⁻¹). The maximum yield observed at this temperature and at a neutral pH was 0.21 mg of biomass per milligram of substrate. Batch experiments indicated that biodegradation can be achieved at low temperatures; however, the biodegradation rate at room temperature (23°C) and neutral pH was 5 times faster than that observed at 4°C. Biodegradation at various pH conditions indicated a maximum specific growth rate of 1.69 day⁻¹ and yield (0.41 mg mg⁻¹) at a pH of 10.     

Russian wheat aphid (Hemiptera: Aphididae) reproduction and development on five noncultivated grass hosts

The Russian wheat aphid, Diuraphis noxia (Kurdjumov), is a small grains pest of worldwide economic importance. The Russian wheat aphid is polyphagous and may encounter differential selective pressures from noncultivated grass hosts. Aphid biotypic diversity can disrupt the progress of plant breeding programs, leading to a decreased ability to manage this pest. The goal of this research was to quantify Russian wheat aphid biotype 2 (RWA2) reproductive and development rates on five common noncultivated grass hosts to gain information about host quality, potential refuges, and sources of selection pressure. First, RWA2 reproduction was compared on crested wheatgrass (Agropyron cristatum, (L.) Gaertn.), intermediate wheatgrass (Elytrigia intermedia, (Host) Nevski), slender wheatgrass (Elymus trachycaulus, (Link) Gould ex Shinners), western wheatgrass (Pascopyrum smithi, (Rydb.) A. L?ve), and foxtail barley (Hordeum jubatum, (L.) Tesky) at 18–24°C. Second, RWA2 reproduction was compared on intermediate and crested wheatgrass at three temperature regimes 13–18°C, 18–24°C, and 24–29°C. At moderate temperatures (18–24°C), the intrinsic rate of increase values for all five hosts ranged from 0.141 to 0.199, indicating the possibility for strong population sources on all tested hosts. Aphids feeding on crested and intermediate wheatgrass at the 13–18°C temperature had lower fecundity, less nymph production days, longer generational times, and lower intrinsic rate of increase than aphids feeding at the 18–24°C temperature regime. Aphids feeding at 24–29°C did not survive long enough to reproduce. The positive intrinsic rates of increase in Russian wheat aphid on the wheatgrasses suggest that these grasses can support aphid populations at moderate to low temperatures.     

Isolation and characterization of a novel thermophilic Bacillus strain degrading long-chain n-alkanes

A thermophilic Bacillus strain NG80-2 growing within the temperature range of 45–73°C (optimum at 65°C) was isolated from a deep subterranean oil-reservoir in northern China. The strain was able to utilize crude oil and liquid paraffin as the sole carbon sources for growth, and the growth with crude oil was accompanied by the production of an unknown emulsifying agent. Further examination showed that NG80-2 degraded and utilized only long-chain (C15–C36) n-alkanes, but not short-chain (C8–C14) n-alkanes and those longer than C40. Based on phenotypic and phylogenic analyses, NG80-2 was identified as Geobacillus thermodenitrificans. The strain NG80-2 may be potentially used for oily-waste treatment at elevated temperature, a condition which greatly accelerates the biodegradation rate, and for microbial enhancing oil recovery process.Lei Wang, Yun Tang and Shuo Wang contributed equally to this study.     

Thermoregulation in Antarctic fulmarine petrels

We measured resting metabolic rates at air temperatures between ca. −5 and 30 °C in snow petrels (Pagodroma nivea), cape petrels (Daption capense), Antarctic petrels (Thalassoica antarctica), and Antarctic fulmars (Fulmarus glacialoides). We measured seven age classes for each species: adults, and nestlings that were 3, 8, 15, 28, 35, and 42 days old. Basal metabolic rate (BMR) and thermal conductance (C) of adults averaged, respectively, 140% and 100% of values predicted allometrically for nonpasserine birds. Minimum metabolic rates of unfasted nestlings aged 15–42 days averaged, respectively, 97% and 98% of predicted adult BMR in Antarctic petrels and snow petrels, versus 119% and 126% of predicted in Antarctic fulmars and cape petrels. Nestlings of the southerly breeding snow petrel and Antarctic petrel were relatively well insulated compared with nestlings of other high-latitude seabirds. Adult lower critical temperature (T_lc) was inversely related to body mass and averaged 9 °C lower than predicted allometrically. As nestlings grew, their T_lc decreased with increasing body mass from ca. 14 to 22 °C (depending upon species) at 3 days of age, to −4 to 8 °C when nestlings attained peak mass. Nestling T_lc subsequently increased as body mass decreased during pre-fledging weight recession. Nestling T_lc was close to mean air temperature from the end of brooding until fledging in the three surface nesting species. Accepted: 12 July 2000     

Mitochondrial function in Antarctic notothenioid fishes that differ in the expression of oxygen-binding proteins

State III respiration rates were measured in mitochondria isolated from hearts of Antarctic notothenioid fishes that differ in the expression of hemoglobin (Hb) and myoglobin (Mb). Respiration rates were measured at temperatures between 2 and 40°C in Gobionotothen gibberifrons (+Hb/+Mb), Chaenocephalus aceratus (–Hb/–Mb) and Chionodraco rastrospinosus (–Hb/+Mb). Blood osmolarity was measured in all three species and physiological buffers prepared for isolating mitochondria and measuring respiration rates. Respiration rates were higher in mitochondria from G. gibberifrons compared to those from C. aceratus at 2°C, but were similar among all species at temperatures between 10 and 26°C. Respiration rates were significantly lower in icefishes at 35 and 40°C compared to G. gibberifrons. The respiratory control ratio of isolated mitochondria was lower in C. aceratus compared to G. gibberifrons at all temperatures below 35°C. At 35 and 40°C, mitochondria were uncoupled in all species. The Arrhenius break temperature of state III respiration was similar among all three species (30.5 ± 0.9°C) and higher than values previously reported for Antarctic notothenioids, likely due to the higher osmolarity of buffers used in this study. These results suggest that differences in mitochondrial structure, correlated with the expression of oxygen-binding proteins, minimally impact mitochondrial function.     

Kinetic analysis of the template effect in ribooligoguanylate elongation

We have undertaken a complete kinetic analysis of the template-directed oligoguanylate synthesis originated in Orgel's laboratory (Inoue and Orgel, 1982). The reaction of guanosine 5′-phospho-2-methylimidazolide, 2-MelmpG, with ribooligoguanylates all 3′–5′ linked, designatedn ³ withn=7−12, was studied in the presence/absence of the complementary template polycytidylic acid, poly(C). Conditions were chosen where poly(C) and 2-MelmpG are in large excess over the oligoguanylate. In the absence of the template at 37 °C the reaction leads to three isomeric oligomers that are elongated by one monomer unit. They are the 3′–5′ linked, (n+1)³, the 2′–5′ linked, (n+1)², and the pyrophosphate product, (n+1) ^p , formed in an approximate ratio 1:2:5. In the presence of the template the reaction is 20-fold faster and yields productsn+1,n+2,n+3 etc. as long as 2-MelmpG is available. Most importantly the formation of the natural, 3′–5′ linked isomer, is enhanced selectively by 140-fold at 37 °C. Qualitative observations allow the conclusion that this enhancement is temperature dependent and increases with decreasing temperature. For example, at 1 °C only the 3′–5′ linked isomers were detected. Initial rates for the disappearance of then ³ oligoguanylate were determined at 1, 23, and 37 °C. It was found that the pseudo-first order rate constant for oligoguanylate elongation was linearly proportional to the 2-MelmpG concentration. This implies that the reaction complex poly(C)·n ³·2-MelmpG does not accumulate under the reaction conditions, a conclusion which is also supported by infrared data (Miles and Frazier, 1982). The implication of the above results with respect to chemical evolution is that lower temperatures, i.e., close to freezing, enhance the regioselectivity of these template-directed reactions and that one way to improve replication models may be sought in finding conditions that favor stable reaction complexes. NASA — National Research Council Research Fellow.