Bacterial processes of the methane cycle in the bottom sediments of Baikal lake

The activity of methanogenic and methanotrophic bacteria was evaluated in bottom sediments of Lake Baikal. Methane concentration in Baikal bottom sediments varied from 0.0053 to 81.7 ml/dm3. Bacterial methane was produced at rates of 0.0004-534.7 microliters CH4/(dm3 day) and oxidized at rates of 0.005-1180 microliters CH4/(dm3 day). Peak methane production and oxidation were observed in Frolikha Bay near a methane vent. Methane was emitted into water at rates of 49.2-4340 microliters CH4/(m2 day). Rates of bacterial methane oxidation in near-bottom water layers ranged from 0.002 to 1.78 microliters/(1 day). Methanogens and methanotrophs were found to play an important role in the carbon cycle through all layers of sediments, particularly in the areas of methane vent and gas-hydrate occurrence.     

光照与氮磷营养盐的协同作用对海带幼苗释放可溶性有机碳的影响

文章以海带(Saccharina japonica)幼苗为实验材料, 对比了其在自然海水+50%海面光强、自然海水+100%海面光强、营养盐加富海水+50%海面光强、营养盐加富海水+100%海面光强4种条件下的溶解有机碳(DOC)释放速率, 以揭示光照与营养盐的协同作用对大型藻类释放DOC的影响机制。研究发现, 在自然海水条件下, 50%与100%海面光强照射下海带幼苗DOC释放速率分别为(11.67±3.07)和(22.65±4.58) μmol/(g·h), 随着光强增加, 释放DOC速率显著提升(P＜0.05), 氧气净释放速率显著增大(P＜0.05), 且二者光谱斜率差异显著(P＜0.05); 在营养盐加富海水条件下, 50%与100%海面光强照射下海带幼苗DOC释放速率分别为(30.88±7.96)和(39.03±14.78) μmol/(g·h), 随着光强增加, 释放DOC速率提升不显著(P＞0.05), 氧气净释放速率显著提高79.24%(P＜0.05), 二者光谱斜率差异不显著(P＞0.05)。结果表明, 在寡营养条件下(自然海水), 海带幼苗释放DOC速率与光照强度呈正相关, 表现为“溢出”机制; 在富营养条件下, 海带幼苗释放DOC速率与光照强度不相关, 表现为“扩散”机制。海带幼苗释放DOC同时受到“溢出”和“扩散”两种机制的调控, 何种机制占主导取决于营养水平。     

N-trimethyl chitosan chloride-coated liposomes for the oral delivery of curcumin

The aims of this study were to design the formulation of curcumin (CUR) liposomes coated with N-trimethyl chitosan chloride (TMC) and to evaluate in vitro release characteristics and in vivo pharmacokinetics and bioavailability of TMC-coated CUR liposomes in rats. The structure of synthesized TMC was examined by infrared spectroscopy, with the presence of trimethyl groups, and by proton nuclear magnetic resonance spectroscopy, indicating the high degree of substitution quaternization (65.6%). Liposomes, composed of soybean phosphotidylcholine, cholestrol, and D-α-tocopheryl polyethylene glycol 1000 succinate, were prepared by a thin-film dispersion method. Characteristics of the CUR liposomes, including entrapment efficiency (86.67%), drug-loading efficiency (2.33%), morphology, particle size (221.4?nm for uncoated liposomes and 657.7?nm for TMC-coated liposomes), and zeta potential (-9.63 mV for uncoated liposomes and +15.64 mV for TMC-coated liposomes) were investigated. Uncoated CUR liposomes and TMC-coated CUR liposomes showed a similar in vitro release profile. Nearly 50% of CUR was released from liposomes, whereas 80% of CUR was released from CUR propylene glycol solution. CUR incorporated into TMC-coated liposomes exhibited different pharmacokinetic parameters and enhanced bioavailability (C(max)?=?46.13 μg/L, t(1/2)?=?12.05 hours, AUC?=?416.58 μg/L·h), compared with CUR encapsulated by uncoated liposomes (C(max)?=?32.12 μg/L, t(1/2)?=?9.79 hours, AUC?=?263.77 μg/L·h) and CUR suspension (C(max)?=?35.46 μg/L, t(1/2)?=?3.85 hours, AUC?=?244.77 μg/L·h). In conclusion, oral delivery of coated CUR liposomes is a promising strategy for poorly water-soluble CUR.     

Long-term performance of peat biofilters treating ethyl acetate, toluene, and its mixture in air

Three laboratory-scale peat biofilters were operated at 90 s empty bed residence time (EBRT) for over a year. Biodegradation of ethyl acetate, toluene, or a 1:1 mixture were investigated. In first stage, inlet concentration was progressively increased from 0.4 to 4.5 g/m(3). The maximum elimination capacity (EC) found for ethyl acetate was 190 gC/m(3).h, and it was not affected by toluene. The maximum EC found for toluene as a sole contaminant was 150 gC/m(3).h, but the presence of ethyl acetate decreased the toluene maximum EC to 80 gC/m(3).h. From respirometry monitoring, values of 3.19 g CO(2)/gC and 3.06 g CO(2)/gC for pure ethyl acetate and pure toluene, respectively, were found, with overall yield coefficients of 0.13 g dry biomass produced per gram ethyl acetate consumed and 0.28 g dry biomass produced per gram toluene consumed. CO(2) production in the 1:1 mixture was successfully simulated. Dynamics of living and dead cells were monitored in four sections of the biofilters. Concentrations ranged between 2.6 x 10(9) and 3.0 x 10(10) cells per gram-dry peat for total bacteria, and 2.4 x 10(9)-1.9 x 10(10) cells per gram-dry peat for living bacteria. At high loads loss of bacterial density in the inlet zones, and increase in the dead cells percentages up to 60% was observed. In second stage, long-term performance at an inlet concentration of 1.5 g/m(3) was evaluated to show the process feasibility. Good agreement with previous data was obtained in terms of EC and CO(2) production. Restoration of living cells proportion was also observed.     

Microbiological processes at the interface of aerobic and anaerobic waters in the deep-water zone of the Black Sea

Chemical and key microbiological processes (assimilation of carbon dioxide, oxidation and formation of methane, and sulfate reduction) occurring at the boundary between the aerobic-anaerobic interface in the deep-water zone of the Black Sea were investigated. Measurements were taken at depths from 90 to 300 m at intervals of 5-10 m. The integral rate of the dark assimilation of carbon dioxide varied from 120 to 207 mg C/(m2 day) with a maximum at the boundary of cyclonic currents. The organic matter (OM) formed from methane comprised less than 5% of the OM formed from carbon dioxide. A comparison between the rates of methane oxidation and methane production suggests that methane that is oxidized at depths from 100 to 300 m was formed in deeper water horizons. The maximum rate of sulfate reduction (1230 mg S/(m2 day)) was observed in the western halistatic region, and the minimum rate (490 mg S/(m2 day)), in the eastern halistatic region. The average rate of hydrogen sulfide production measured at three deep-sea stations amounted to 755 mg S/(m2 day), or 276 g S/(m2 year).     

NaNO3胁迫对两种微囊藻VOCs释放的影响

为了揭示硝酸盐过量积累对藻类产生胁迫后对藻类挥发性有机化合物(VOCs)释放以及水体气味的影响, 研究以形成蓝藻水华的主要种类铜绿微囊藻和水华微囊藻为材料, 在NaNO3胁迫下, 对其细胞生长和释放的VOCs进行测定分析。结果表明, NaNO3胁迫24h后, 铜绿微囊藻和水华微囊藻细胞生长均受到明显影响, 与对照相比细胞密度分别降低了29.6%和43.0%。在正常条件下, 铜绿微囊藻和水华微囊藻分别释放出26和27种化合物, 其主要类型是硫化物、烃类、萜烯类、苯类、醛类和酯类化合物。在NaNO3胁迫下, VOCs含量均明显增加, 其中铜绿微囊藻释放的此6类VOCs含量分别增加了60.5%、14.3%、136.6%、92.1%、730.0%和120.7%, 水华微囊分别增加了172.7%、162.5%、154.0%、55.9%、51.2%和109.4%。此外, 铜绿微囊藻VOCs中出现4种新成分, 水华微囊藻VOCs中出现1种新成分。由此可见, 硝酸盐过量积累对藻细胞产生胁迫后会诱导其释放出大量VOCs, 从而增加水体气味、破坏水质。       

冷蒿挥发性有机化合物主要成分分析及其地上部分结构研究

冷蒿(Artemisia frigida)挥发性有机化合物(volatile organic compounds, VOCs)具有特殊气味, 在植物受损伤时, 此气味会更加浓烈。该文通过对未损伤与损伤冷蒿VOCs成分分析、地上部分结构观察, 初步揭示了冷蒿VOCs释放与结构之间的关系。结果表明, 未损伤冷蒿VOCs主要含有22种化合物, 其主要成分是莰烯(14.27%)、(E)-乙酸-3-己烯酯(10.85%)、对-伞花烃(9.05%)、桉树脑(39.80%)、α-萜品醇(10.04%)、β-萜品醇(2.48%)、樟脑(5.66%)和(R)-(-)-对薄荷-1-烯-4-醇(3.84%)。损伤较未损伤冷蒿VOCs增加了12种物质, 其中相对含量大于1%的化合物分别为顺-3-己烯醛(1.15%)、2-己烯醛(1.34%)、顺-牻牛儿醇(2.66%)、冰片(4.47%)、(1R,4R)(+)-对-薄荷-2,8-二烯(9.15%)、乙酸冰片酯(1.37%)和4(14), 11-桉叶双烯(1.30%)。冷蒿叶片中栅栏组织发达, 叶柄内具有2-3处栅栏组织, 并且栅栏组织中都具有发达的气室, 同时气室与气孔相连。因此, 损伤较未损伤冷蒿VOCs种类和浓度增多的原因可能为: 冷蒿VOCs合成后大量储存于气室中, 当叶片损伤时, VOCs大量释放出来, 同时合成释放一些新的VOCs, 致使损伤冷蒿VOCs种类和浓度增加。     

Kinetics of uptake of phosphates and nitrates by marine multicellular algae <Emphasis Type="Italic">Gelidium latifolium</Emphasis> (Grev.) Born. et Thur.

We studied nonstationary kinetics of the uptake of phosphates and nitrates by the red marine algae Gelidium latifolium (Grev.) Born et Thur. and calculated constants of the Michaelis-Menten equation for these elements. In the area of 0–3 μM, the kinetics of phosphate consumption had the following coefficients: maximum rate of uptake 0.8 μmol/(g h), constant of half-saturation 1.745 μM. For nitrate nitrogen at 0–30 μM, an adaptive strategy of uptake kinetics was noted with change of the equation parameters with time: after 1 h, the maximum rate of uptake was 5.1 μmol/(g h) and constant of half-saturation 19 μM, while within 2 h, the maximum rate of uptake significantly increased. This could be related to the synthesis of nitrate reductase. Coupled with the uptake of nitrates, nonstationary kinetics of the release of nitrates in the surrounding medium had a one-peak pattern: the maximum concentration of nitrites in the medium and the time of its achievement increased with the initial concentration of nitrates. The maximum concentration of nitrites was 6 to 14% of the initial concentration in the medium.     

Microbial processes at the aerobic-anaerobic interface in the deep-water zone of the black sea

Chemical and key microbiological processes (assimilation of carbon dioxide, oxidation and formation of methane, and sulfate reduction) occurring at the aerobic-anaerobic interface in the deep-water zone of the Black Sea were investigated. Measurements were taken at depths from 90 to 300 m at intervals of 5–10 m. The integral rate of the dark assimilation of carbon dioxide varied from 120 to 207 mg C/(m² day) with a maximum at the boundary of cyclonic currents. The organic matter (OM) formed from methane comprised less than 5% of the OM formed from carbon dioxide. A comparison between the rates of methane oxidation and methane production suggests that methane that is oxidized at depths from 100 to 300 m was formed in deeper water horizons. The maximum rate of sulfate reduction (1230 mg S/(m₂ day)) was observed in the western halistatic region, and the minimum rate (490 mg S/(m₂ day)), in the eastern halistatic region. The average rate of hydrogen sulfide production measured at three deep-sea stations amounted to 755 mg S/(m₂ day), or 276 g S/(m₂ year).     

Seasonal dynamics of atmospheric methane oxidation in gray forest soils

Seasonal fluctuations in the methane flow in the soil-atmosphere system were determined for gray forest soils of Central Russia. Consumption of atmospheric methane was found to exceed methane emission in gray forest soils under forest and in agrocenosis. The average annual rates of atmospheric methane consumption by the soil under forest and in agrocenosis were 0.026 and 0.008 mg CH4-C/(m2 h), respectively. The annual rate of atmospheric methane oxidation in the gray forest soils of Moscow oblast was estimated to be 0.68 kton. Seasonal fluctuations in the methane oxidation activity were due to changes in the hydrothermal conditions and in the reserves of readily decomposable organic matter and mineral nitrogen, as well as to changes in the activity of methane oxidizers.     

Mechanism of steroid action in inflammation: Inhibition of prostaglandin synthesis and release

Acute arthritis was induced by injection of cell-free extract of group A Streptococci into the knee joints of mature male rats. Slices of control and inflamed synovia were incubated for 30 to 240 minutes and the rate of prostaglandin E (PGE) released into the medium was measured by radioimmunoassay. PGE release from inflamed synovia was 5–8 fold higher than that in normal tissue. Incubation of inflamed synovia with corticosterone acetate, dexamethasone or prednisone (100 μg/ml) for one or four hours reduced PGE release by 33% and 55% respectively. Lower concentrations of corticosterone (10 – 30 μg/ml) were ineffective. Aldosterone and progesterone (100 μg/ml) had no effect on PGE release throughout the incubation period. Chloroquine (10 μg/ml) inhibited PGE release from inflamed synovia by 50%. Indomethacin (1 μg/ml) abolished PGE release by 90%. Corticosterone, dexamethasone and prednisone reduced PGE content of inflamed synovia by approximately 45% during a 4-h incubation period. Aldosterone and progesterone were ineffective, while indomethacin reduced PGE content by 70%. The suppressive action of corticosterone on PGE release was prevented by addition to the medium of arachidonic acid (2 μg/ml). By contrast, the inhibitory action of indomethacin was not affected by provision of exogenous substrate. We suggest that glucocorticosteroids reduce PGE release by limiting the availability of the substrate for prostaglandin biosynthesis, and this may well explain some of their anti-inflammatory properties.     

改良内皮抑素对人脐静脉内皮细胞抑制作用的实验研究

目的:探讨改良内皮抑素(RGDRGD-ES)对人脐静脉内皮细胞(HUVEC)的抑制作用,摸索RGDRGD-ES对HUVEC细胞抑制作用的相对最佳作用浓度和时间。方法:通过快速定点诱变PCR方法获得含有RGDRGD膜序的改良人内皮抑素基因,并构建其原核表达载体。表达、纯化改良内皮抑素(RGDRGD-ES),运用MTT法和流式细胞仪检测RGDRGD-ES对人脐静脉内皮细胞的抑制作用。结果:1.诱变了ES基因,获得了改良的RGDRGD-ES基因,并成功构建其原核表达载体。2.获得了RGDRGD-ES蛋白。3.改良的RGDRGD-ES能够有效抑制人脐静脉内皮细胞的生长(P<0.01);抑制率随着药物浓度(10μg/ml、20μg/ml、30μg/ml)的增加和作用时间(24 h、48 h、72 h)的延长而逐渐增加,具有浓度和时间依赖性(P<0.01);而30μg/ml与40μg/ml、50μg/ml组间、72 h与96 h组间无明显差异(P>0.05)。4.细胞凋亡率(作用24 h)具有药物浓度(10μg/ml、20μg/ml、30μg/ml)依赖性(P<0.01),30μg/ml与40μg/ml、50μg/ml组间凋亡率无明显差异(P>0.05)。结论:成功构建了改良RGDRGD-ES基因的原核表达载体,RGDRGD-ES蛋白在30μg/ml浓度作用72小时条件下能够有效抑制人脐静脉内皮细胞的生长,改良内皮抑素(RGDRGD-ES)对HUVEC的抑制作用较ES明显提高。     

N-trimethyl chitosan chloride-coated liposomes for the oral delivery of curcumin

The aims of this study were to design the formulation of curcumin (CUR) liposomes coated with N-trimethyl chitosan chloride (TMC) and to evaluate in vitro release characteristics and in vivo pharmacokinetics and bioavailability of TMC-coated CUR liposomes in rats. The structure of synthesized TMC was examined by infrared spectroscopy, with the presence of trimethyl groups, and by proton nuclear magnetic resonance spectroscopy, indicating the high degree of substitution quaternization (65.6%). Liposomes, composed of soybean phosphotidylcholine, cholestrol, and D-α-tocopheryl polyethylene glycol 1000 succinate, were prepared by a thin-film dispersion method. Characteristics of the CUR liposomes, including entrapment efficiency (86.67%), drug-loading efficiency (2.33%), morphology, particle size (221.4?nm for uncoated liposomes and 657.7?nm for TMC-coated liposomes), and zeta potential (–9.63 mV for uncoated liposomes and +15.64 mV for TMC-coated liposomes) were investigated. Uncoated CUR liposomes and TMC-coated CUR liposomes showed a similar in vitro release profile. Nearly 50% of CUR was released from liposomes, whereas 80% of CUR was released from CUR propylene glycol solution. CUR incorporated into TMC-coated liposomes exhibited different pharmacokinetic parameters and enhanced bioavailability (C_max?=?46.13 μg/L, t_1/2?=?12.05 hours, AUC?=?416.58 μg/L·h), compared with CUR encapsulated by uncoated liposomes (C_max?=?32.12 μg/L, t_1/2?=?9.79 hours, AUC?=?263.77 μg/L·h) and CUR suspension (C_max?=?35.46 μg/L, t_1/2?=?3.85 hours, AUC?=?244.77 μg/L·h). In conclusion, oral delivery of coated CUR liposomes is a promising strategy for poorly water-soluble CUR.     

带形蜈蚣藻盘丝体孢子的形成及温度和光照强度对其放散的影响

在实验室条件下, 首次发现了带形蜈蚣藻(Grateloupia turuturu)盘状体产生的丝状体能够形成孢子, 暂命名为“盘丝体孢子”。研究详细观察了该盘丝体孢子的形成过程, 并探讨了不同温度6、12、16、20、24和30℃及不同光照强度10、30、45、60、90和120 μmol/(m2·s)对盘丝体孢子放散的影响。结果表明: (1) 带形蜈蚣藻雌配子体的囊果释放果孢子, 果孢子发育形成盘状体, 盘状体经过诱导再生出单列细胞的丝状体, 丝状体形成多室孢子囊, 并放散出大量盘丝体孢子; (2) 温度和光照强度均对丝状体中盘丝体孢子的放散产生显著影响。在温度为16℃、光照强度为60 μmol/(m2·s)时盘丝体孢子放散量有最大值; (3) 在温度低于12℃或高于24℃时, 盘丝体孢子的放散受到影响, 数量明显减少; (4) 在光照强度低于30 μmol/(m2·s)或高于90 μmol/(m2·s)时, 盘丝体孢子的放散明显受到抑制。研究结果补充了带形蜈蚣藻无性繁殖过程, 为其种质保存、人工育苗及养殖提供更为丰富的理论依据, 为探讨带形蜈蚣藻的起源与演化提供新思路。     

Reduction-Responsive Disassemblable Core-Cross-Linked Micelles Based on Poly(ethylene glycol)-b-poly(N-2-hydroxypropyl methacrylamide)-Lipoic Acid Conjugates for Triggered Intracellular Anticancer Drug Release

Reduction-sensitive reversibly core-cross-linked micelles were developed based on poly(ethylene glycol)-b-poly(N-2-hydroxypropyl methacrylamide)-lipoic acid (PEG-b-PHPMA-LA) conjugates and investigated for triggered doxorubicin (DOX) release. Water-soluble PEG-b-PHPMA block copolymers were obtained with M(n,PEG) of 5.0 kg/mol and M(n,HPMA) varying from 1.7 and 4.1 to 7.0 kg/mol by reversible addition-fragmentation chain transfer (RAFT) polymerization. The esterification of the hydroxyl groups in the PEG-b-PHPMA copolymers with lipoic acid (LA) gave amphiphilic PEG-b-PHPMA-LA conjugates with degrees of substitution (DS) of 71-86%, which formed monodispersed micelles with average sizes ranging from 85.3 to 142.5 nm, depending on PHPMA molecular weights, in phosphate buffer (PB, 10 mM, pH 7.4). These micelles were readily cross-linked with a catalytic amount of dithiothreitol (DTT). Notably, PEG-b-PHPMA(7.0k)-LA micelles displayed superior DOX loading content (21.3 wt %) and loading efficiency (90%). The in vitro release studies showed that only about 23.0% of DOX was released in 12 h from cross-linked micelles at 37 °C at a low micelle concentration of 40 μg/mL, whereas about 87.0% of DOX was released in the presence of 10 mM DTT under otherwise the same conditions. MTT assays showed that DOX-loaded core-cross-linked PEG-b-PHPMA-LA micelles exhibited high antitumor activity in HeLa and HepG2 cells with low IC(50) (half inhibitory concentration) of 6.7 and 12.8 μg DOX equiv/mL, respectively, following 48 h incubation, while blank micelles were practically nontoxic up to a tested concentration of 1.0 mg/mL. Confocal laser scanning microscope (CLSM) studies showed that DOX-loaded core-cross-linked micelles released DOX into the cell nuclei of HeLa cells in 12 h. These reduction-sensitive disassemblable core-cross-linked micelles with excellent biocompatibility, superior drug loading, high extracellular stability, and triggered intracellular drug release are promising for tumor-targeted anticancer drug delivery.     

Effects of nonylphenol on the production of progesterone on the rats granulosa cells

We investigated the effects of nonylphenol (NP) on release of progesterone (PG) by granulosa cells (GCs) of rats in vitro and in vivo. First, GCs were treated with different doses of NP for 2-24 h alone or with human chorionic gonadotropin (hCG). Maximal PG secretion at 8 h noted, GCs were treated for 2 h with hCG, 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP), forskolin, A23187, nifedipine, and pregnelonone to evaluate the NP effects on PG steroidogenesis. Results indicated that all of chemicals except nifedipine stimulated the PG release compared to vehicle, but the stimulatory effects could not be enhanced by different doses of NP. Second, GCs were isolated to react with hCG, 8-Br-cAMP and PD98059 after the immature female rats gavaged with different doses of NP (ONP) for 7 days. PG released significantly when rats treated with oral NP 100 compared to 0 μg/kg/day. Third, GCs collected from the female offspring of mother rats which gavaged with NP 100 μg/kg/day for 21 days during pregnancy (MONP) reacted with different doses of chemicals. The results showed that PG release in the presence of chemicals was significantly higher in ONP and MONP groups; however, this stimulation was not noted by dose-dependent. The plasma concentration of PG was higher in ONP (100 μg/kg/day) and the offspring of MONP groups. The steroidogenic acute regulatory (StAR) protein expressed higher in all three groups by Western blotting. This study results indicated that low dose of NP stimulated PG release in rat GCs by activation of StAR protein.     

产琥珀酸重组大肠杆菌的发酵性能研究

研究了重组大肠杆菌JM001(△ppc)/pTrc99a-pck发酵产琥珀酸的性能,结果表明厌氧条件下其耗糖能力和产酸能力分别为对照菌株JM001的4.2倍和15.3倍。进一步优化发酵条件表明：采用接入菌泥的发酵方式比按照10%接种量转接厌氧发酵的效果要好,琥珀酸的对葡萄糖的质量收率提高了约10%,且副产物乙酸的量进一步降低。初始葡萄糖浓度高于60g/L时会对菌株的生长和产酸产生抑制,且浓度越高,抑制作用越明显。7L发酵罐放大实验中,整个厌氧发酵阶段葡萄糖的消耗速率为0.42g/(L.h),琥珀酸对葡萄糖的质量收率为67.75%,琥珀酸的生产强度为0.28g/(L.h)。     

Biogeochemical cycle of methane in the northwestern shelf of the Black Sea

Seasonal investigations of methane distribution and rates of its oxidation and generation in the water column and sediments of the Black Sea northwestern shelf were carried out within the framework of the interdisciplinary projects "European River-Ocean Systems" (EROS-2000, EROS-21) and "Biogenic Gases Exchange in the Black Sea" (BigBlack) in August 1995, May 1997, and December 1999. Experiments that involved the addition of 14CH3COONa and 14CO2 to sediment samples showed the main part of methane to be formed from CO2. Maximum values of methane production (up to 559 mumol/(m2 day)) were found in coastal sediments in summer time. In winter and spring, methane production in the same sediments did not exceed 3.6-4.2 mumol/(m2 day). The delta 13C values of methane ranged from -70.7 to -81.8@1000, demonstrating its microbial origin and contradicting the concept of the migration of methane from cold seeps or from the oil fields located at the Black Sea shelf. Experiments that involved the addition of 14CH4 to water and sediment samples showed that a considerable part of methane is oxidized in the upper horizons of bottom sediments and in the water column. Nevertheless, it was found that, in summer, part of methane (from 6.8 to 320 mumol/(m2 day)) arrives in the atmosphere.     

Microbial leaching of arsenic from low‐sulfide gold mine material

Drainages from high‐sulfide tailings near abandoned lode deposits in Alaska, U.S.A., and Yukon, Canada, were found to be acidic, to contain large numbers of Thiobacillus ferrooxidans, and to have high concentrations of dissolved arsenic. Drainages from active placer gold mines are not acidic, but T. ferrooxidans and concentrations of dissolved arsenic exceeding 10 μg/L are found in some streams affected by placer mine drainage. Placer mine material containing low amounts of sulfides (326 (μg/g) and moderately high amounts of arsenic (700 μg/g) was leached with growing cultures of T. ferrooxidans, T. ferrooxidans‐spent filtrate, and acid ferric sulfate. The results showed that while more arsenic was released from this material by growing cultures of T. ferrooxidans than by abiotic controls, acid ferric sulfate released much more arsenic than did either growing cultures of T. ferrooxidans or spent culture filtrate containing oxidized iron. Cation exchange chromatography showed that oxidized iron from T. ferrooxidans culture filtrate is chemically less reactive than the iron in aqueous solutions of ferric sulfate salt. These results indicate that arsenic release from both high‐ and low‐sulfide mine wastes is enhanced biologically, but that rates and amounts of arsenic release are primarily controlled by iron species.     

Carbon Dioxide Assimilation and Methane Oxidation in Various Zones of the Rainbow Hydrothermal Field

Rates of carbon dioxide assimilation and methane oxidation were determined in various zones of the Rainbow Hydrothermal Field (36°N) of the Mid-Atlantic Ridge. In the plume above the hydrothermal field, anomalously high methane content was recorded, the microbial population density (up to 10⁵ cells/ml) was an order of magnitude higher than the background values, and the CO₂ assimilation rate varied from 0.01 to 1.1 g C/(l day). Based on the data on CO₂ assimilation, the production of organic carbon due to bacterial chemosynthesis in the plume was calculated to be 930 kg/day or 340 tons/year (about 29% of the organic carbon production in the photic zone). In the black smoke above active smokers, the microbial population density was as high as 10⁶ cells/ml, the rate of CO₂ assimilation made up 5–10 g C/(l day), the methane oxidation rate varied from 0.15 to 12.7 l/(l day), and the methane concentration ranged from 1.05 to 70.6 l/l. In bottom sediments enriched with sulfides, the rate of CO₂ assimilation was at least an order of magnitude higher than in oxidized metal-bearing sediments. At the base of an active construction, whitish sediment was found, which was characterized by a high methane content (92 l/dm³) and a high rate of methane oxidation (1.7 l/(dm³ day)).