In situ microbial ecology of hydrothermal vent sediments

Abstract Lipid analysis of a preliminary sampling of the Endeavor Ridge hydrothermal vent site was performed in order to estimate the extent and nature of the diversity of the microbial community. The vent microbial community was found to be highly variable in density and composition. Evidence was found for a dense microbial community of archaebacteria and possibly Thiobacilli in the interior of the flange of a black smoker, a red Beggiatoa -type colony in a sediment sample, and large amounts of polyenoic fatty acids of the type previously found in barophilic eubacteria. Lipid analysis provided a 'snapshot' of the in situ biomass, community structure, and metabolic status of the microbial community, a valuable addition to the techniques available to the microbial ecologist.     

Dehalogenation of environmental pollutants in microbial electrolysis cells with biogenic palladium nanoparticles

Purpose of work Hydrodehalogenation of persistent pollutants, such as the groundwater contaminants trichloroethylene and diatrizoate, are catalyzed by biogenic Pd nanoparticles. As H₂ gas supply for the dehalogenation reactions is still the limiting factor, this study examines in situ H₂ production in the cathode of a microbial electrolysis cell.     

In situ bioremediation of monoaromatic pollutants in groundwater: a review

Monoaromatic pollutants such as benzene, toluene, ethylbenzene and mixture of xylenes are now considered as widespread contaminants of groundwater. In situ bioremediation under natural attenuation or enhanced remediation has been successfully used for removal of organic pollutants, including monoaromatic compounds, from groundwater. Results published indicate that in some sites, intrinsic bioremediation can reduce the monoaromatic compounds content of contaminated water to reach standard levels of potable water. However, engineering bioremediation is faster and more efficient. Also, studies have shown that enhanced anaerobic bioremediation can be applied for many BTEX contaminated groundwaters, as it is simple, applicable and economical.

This paper reviews microbiology and metabolism of monoaromatic biodegradation and in situ bioremediation for BTEX removal from groundwater under aerobic and anaerobic conditions. It also discusses the factors affecting and limiting bioremediation processes and interactions between monoaromatic pollutants and other compounds during the remediation processes.     

Online and in situ monitoring of environmental pollutants: electrochemical biosensing of cadmium

Online sensitive monitoring of gene expression is essential for understanding microbial life and microbial communities, especially under stress-inducing conditions, such as the presence of environmental pollutants. We describe here a novel use of promoter-based electrochemical biosensing for online and in situ monitoring of gene expression in response to pollutants. As a model system, we used a cadmium-responsive promoter from Escherichia coli fused to a promoterless lacZ gene, which was monitored using an electrochemical assay of β-galactosidase activity. This whole-cell biosensor could detect, within minutes, nanomolar concentrations of cadmium in water, sea water and soil samples, and it can be used for continuous online and in situ monitoring.     

Genetically engineered microbial biosensors for in situ monitoring of environmental pollution

Microbial biosensors are compact, portable, cost effective, and simple to use, making them seem eminently suitable for the in situ monitoring of environmental pollution. One promising approach for such applications is the fusion of reporter genes with regulatory genes that are dose-dependently responsive to the target chemicals or physiological signals. Their biosensor capabilities, such as target range and sensitivity, could be improved by modification of regulatory genes. Recent uses of such genetically engineered microbial biosensors include the development of portable biosensor kits and high-throughput cell arrays on chips, optic fibers, or other platforms for on-site and on-line monitoring of environmental pollution. This mini-review discusses recent advances in microbial biosensors and their future prospects, with a focus on the development and application of genetically modified microbial biosensors for in situ environmental monitoring.     

In situ studies of metabolism in benthic reef communities

Summary 1. Rates of net photosynthesis and respiration were determined in situ forTridacna and coral species and their contained zooxanthellae at depths from 9 to 18 m.2. Integrated daily total net photosynthesis to respiration ratios (P/R ratio) were calculated from these data to obtain the potential contribution of algal photosynthesis to the energy budget of the coral-algal symbiotic association.3. The integrated daily P/R ratios varied between 0.79 and .89. Maximum ratios of photosynthesis to respiration rates ranged from 1.15 forMussa arrgulosa to 2.91 forManicina areolata.4. Similar measurements were made on mixed benthic communities off southeastern Florida (USA) in a clean, unpolluted area and in an area influenced by the effluent of Biscayne Bay (USA). Very significant differences were found.

---

In-situ-Studien über den Stoffwechsel benthonischer Lebensgemeinschaften des Korallenriffs

Kurzfassung Im Rahmen mehrerer amerikanischer Unterwasser-Forschungsprogramme wurden Stoffwechseluntersuchungen in verschiedenen Korallenriffen an Benthostieren durchgeführt, die in symbiotischer Partnerschaft mit Zooxanthellen leben. An Korallen- undTridacna-Arten wurden in situ die Beziehungen zwischen Nettophotosynthese und Sauerstoffverbrauch (P/R-Verhältnis) gemessen. Als Maximalwert wurde beiManicina areolata ein P/R-Verhältnis von 2,9 ermittelt. Die auf einen Zeitraum von 24 Stunden bezogenen Durchschnittswerte lagen zwischen 0,79 und 0,89. Es wurde festgestellt, daß die photosynthetische Aktivität der Korallen in verunreinigten Riffgebieten stark absinkt.

     

养殖水质原位自净微生物诱导及复合应用

本文采用原位诱导有益微生物（污水菌、芽胞杆菌、硝化菌和副球菌等）,复合添加外源的有益微生物（金藻、栅藻、硅藻、芽胞杆菌、光合菌、酵母菌和EM（effective microorganisms）菌等）,在养殖水体中建立稳定的有益微生物复合菌群,使水体中亚硝酸氮和氨氮清除率分别可达100%和99%。并进一步利用这些菌群在小红鲫鱼（red crucian carp）和南美白对虾（Penaeus vannamei）养殖中进行原位水质净化应用。在小红鲫鱼养殖水质原位自净中,无需清污和换水,就可长期维持水环境完全稳定,连续养殖50 d以上,水中未检测出亚硝酸氮,氨氮低于0.2 mg/L,稳定在优质安全的养殖环境;在南美白对虾养殖中,投菌后初期水体亚硝酸氮较快下降,第10 d后氨氮浓度也降至养殖安全范围内,形成稳定安全的养殖水质环境。实验效果显著,表明微生物菌群原位水质自净技术具有推广应用前景。     

In situ contaminants and environmental assessment — An ecological summary

This paper outlines the origins of the concept of environmental impact assessment and attempts to explain why the scientific basis has not developed as well as the procedural aspects. It raises the question of the role of ecological science in environmental impact assessment and discusses the compatability of the objectives of the ecologist with those of the decision makers. A conceptual framework for the consideration of the problems of in situ contaminants is presented within the context of environmental assessment. Recent developments regarding the support of assessment research are discussed and future priorities are suggested.     

In situ hydrogen consumption kinetics as an indicator of subsurface microbial activity

There are few methods available for broadly assessing microbial community metabolism directly within a groundwater environment. In this study, hydrogen consumption rates were estimated from in situ injection/withdrawal tests conducted in two geochemically varying, contaminated aquifers as an approach towards developing such a method. The hydrogen consumption first-order rates varied from 0.002 nM h(-1) for an uncontaminated, aerobic site to 2.5 nM h(-1) for a contaminated site where sulfate reduction was a predominant process. The method could accommodate the over three orders of magnitude range in rates that existed between subsurface sites. In a denitrifying zone, the hydrogen consumption rate (0.02 nM h(-1)) was immediately abolished in the presence of air or an antibiotic mixture, suggesting that such measurements may also be sensitive to the effects of environmental perturbations on field microbial activities. Comparable laboratory determinations with sediment slurries exhibited hydrogen consumption kinetics that differed substantially from the field estimates. Because anaerobic degradation of organic matter relies on the rapid consumption of hydrogen and subsequent maintenance at low levels, such in situ measures of hydrogen turnover can serve as a key indicator of the functioning of microbial food webs and may be more reliable than laboratory determinations.     

Effects of four aromatic organic pollutants on microbial glucose metabolism and thymidine incorporation in marine sediments

The metabolism of D-[U-14C]glucose and the incorporation of [methyl-3H]thymidine by aerobic and anaerobic marine sediment microbes exposed to 1 to 1,000 ppm anthracene, naphthalene, p,p'-dichlorodiphenyltrichloroethane, and pentachlorophenol were examined. Cell-specific rates of [14C]glucose metabolism averaged 1.7 X 10(-21) and 0.5 X 10(-21) mol/min per cell for aerobic and anaerobic sediment slurries, respectively; [3H]thymidine incorporation rates averaged 43 X 10(-24) and 9 X 10(-24) mol/min per cell for aerobic and anaerobic slurries, respectively. Aerobic sediments exposed to three of the organic pollutants for 2 to 7 days showed recovery of both activities. Anaerobic sediments showed little recovery after 2 days of pre-exposure to the pollutants. We conclude that (i) anaerobic sediments are more sensitive than aerobic sediments to pollutant additions; (ii) [3H]thymidine incorporation is more sensitive to pollutant additions than is [14C]glucose metabolism; and (iii) the toxicity of the pollutants increased in the following order: anthracene, p,p'-dichlorodiphenyltrichloroethane, naphthalene, and pentachlorophenol.     

Oxidative stress from environmental pollutants

Recently progress has been made on O₂ toxicity and pathology related to numerous environmental contaminants in insects. The pro-oxidants studied included: dioxin, paraquat, and an assorted array of quinones, 8-methoxypsorlen, arsenic, and mercury. The responses to these oxidants are diverse, but they arise from the reactive oxygen species. These pro-oxidants in insects cause lipid peroxidation, protein and enzyme oxidation, and GSH depletion. Potentially, they may also cause DNA oxidation, and form DNA adducts. Oxidative challenge is alleviated by antioxidant compounds, but more importantly by the induction of antioxidant enzymes, which are crucial for the termination of O₂ radical cascade and lipid peroxidation chain reaction. Insects exhibit a wasting syndrome under sub-acute stress. In acute toxicity vital physiological processes impaired are hemolymph melanization and diuresis. Thus, insects resemble vertebrates in both the response to oxidative stress and its pathological consequences. These results raise the prospect that insects may serve as non-mammalian model species for monitoring the oxidative-stress component of environmental toxicity. © 1995 Wiley-Liss, Inc.     

In situ visualization of high genetic diversity in a natural microbial community.

Simultaneous in situ visualization of seven distinct bacterial genotypes, all affiliated with the phylogenetically narrow group of beta-1 Proteobacteria, was achieved in activated sludge. This finding indicates that the high diversity found in the same sample by direct rRNA sequence retrieval was indeed present in this complex community. By the combination of comparative rRNA sequence analysis, in situ hybridization with fluorescently labeled, rRNA-targeted oligonucleotides and confocal laser scanning microscopy several microbial populations can be analyzed for abundance, relative spatial distribution and phylogeny directly at their site of action without prior cultivation.     

Synthetic oligonucleotide probes for detection of mercury-resistance genes in environmental freshwater microbial communities in response to pollutants

Mercury-resistance genes were detected byin situ hybridization using new synthetic oligonucleotide probes specific formerA andmerB genes according to the published sequences of the corresponding enzymes. These DNA probes were used for the detection of specific mercury-resistant microorganisms isolated from the Rhine River which had been polluted 3 years previously in 1986. Mercuric reductase and organomercurial lyase genes persist in the bacterial genome even after the disappearance of the pollutant but are absent in axenic amoebae. A total of 49 bacterial isolates showed DNA homologies with the³²P-labelled DNA probes and 15 free-living amoebae were selected due to their harboured symbiotic mercury-resistant bacteria.     

Degradation of environmental pollutants byPhanerochaete chrysosporium

The white rot fungi appear to be unique in their ability to degrade lignin by the secretion of hydrogen peroxide and a family of peroxidases now referred to as lignin peroxidases or simply ligninases. The fact that these enzymes are naturally secreted and seem to be capable of initiating the oxidation of lignin by a free-radical mechanism led to the proposal and demonstration that the white rot fungi are able to degrade a wide variety of normally very recalcitrant environmental pollutants. The mineralization of chemicals byPhanerochaete chrysosporium does seem to be dependent upon the lignin degrading system. Thus it should be possible to at least initiate degradation extracellularly, eliminating the need for absorption of the chemical. The nonspecific nature of the system gives the potential for oxidation of a wide variety of chemicals and even mixtures of chemicals. As the lignin peroxidases are synthesized and secreted in response to nutrient starvation there is no requirement for conditioning of the organism. Mineralization can occur in either a water or soil matrix using very economical agricultural or wood wastes as nutrients. The lignin peroxidases can be purified from the extracellular fluid quite easily by fast protein liquid chromatography. They are somewhat typical peroxidases but also have some unique properties. The oxidation of some xenobiotics has been demonstrated and cooxidation is also a possible mechanism.     

Effects of four aromatic organic pollutants on microbial glucose metabolism and thymidine incorporation in marine sediments.

The metabolism of D-[U-14C]glucose and the incorporation of [methyl-3H]thymidine by aerobic and anaerobic marine sediment microbes exposed to 1 to 1,000 ppm anthracene, naphthalene, p,p'-dichlorodiphenyltrichloroethane, and pentachlorophenol were examined. Cell-specific rates of [14C]glucose metabolism averaged 1.7 X 10(-21) and 0.5 X 10(-21) mol/min per cell for aerobic and anaerobic sediment slurries, respectively; [3H]thymidine incorporation rates averaged 43 X 10(-24) and 9 X 10(-24) mol/min per cell for aerobic and anaerobic slurries, respectively. Aerobic sediments exposed to three of the organic pollutants for 2 to 7 days showed recovery of both activities. Anaerobic sediments showed little recovery after 2 days of pre-exposure to the pollutants. We conclude that (i) anaerobic sediments are more sensitive than aerobic sediments to pollutant additions; (ii) [3H]thymidine incorporation is more sensitive to pollutant additions than is [14C]glucose metabolism; and (iii) the toxicity of the pollutants increased in the following order: anthracene, p,p'-dichlorodiphenyltrichloroethane, naphthalene, and pentachlorophenol.     

微生物代谢环境难降解性有机物的酶学研究进展

随着人类社会的快速发展,工业化水平不断提高,产生大量的污染物并排放到环境中,给人类的生活和身体健康造成了严重的影响。这些污染物中包含种类繁多的难降解有机物,如多芳香烃(PAHs)、环硝胺类物质(RDX、HMX和CL-20)、多氯联苯(PCBs)及烷烃类化合物等,对自然界的污染危害大。微生物可以消除它们对污染的影响,研究结果表明微生物的代谢或共代谢活动是降解这些物质的有效途径,降解起始阶段需要一些关键酶的参与活动,以氧化还原酶为主。这些氧化还原酶一般与细胞膜上其他的活性组分在一起,形成一个氧化还原系统氧化底物。被氧化的中间物质再通过一系列酶催化继续氧化成三羧酸中间代谢产物被微生物所利用。以下综述了与这些物质降解相关的代谢途径和关键的酶,展望今后在开展这类研究工作时要加强降解微生物的筛选和相关酶学的研究,进一步研究这些污染物的代谢或共代谢途径和机理,为工程化治理环境污染提供依据。     

In situ analysis of native microbial communities in complex samples with high particulate loads

In the present study a procedure combining a cell extraction method and Fluorescence In Situ Hybridization (FISH) for molecular monitoring and quantification of bacteria in soil and aquifer samples is presented. FISH was applied to bacterial cells extracted from the matrix by density gradient centrifugation. This separation method was applied to soil and aquifer samples and produced high cell recovery of 76.5%+/-4.4 and 78.0%+/-3.2, respectively. FISH, performed on the harvested cells, permitted a perfect visualization and quantification of bacteria. This approach is therefore promising for in situ detection of indigenous bacterial communities in complex samples.