Denitrification and Nitrogen Fixation in Alaskan Continental Shelf Sediments

Rates of nitrogen fixation and denitrification were measured in Alaskan continental shelf sediments. In some regions, rates of nitrogen fixation and denitrification appeared to be equal; in other areas, rates were significantly different. Potential rates of denitrification were found to be limited primarily by the available nitrate substrate. Major regional differences in rates of denitrification were not statistically significant, but significant differences were found for nitrogen fixation rates in different regions of the Alaskan continental shelf. Estimated net losses of nitrogen from Bering Sea sediments were calculated as 1.8 × 10¹² g of N/yr. Experimental exposure of continental shelf sediments to petroleum hydrocarbons reduced rates of nitrogen fixation and denitrification in some cases but not others. Long-term exposure was necessary before a reduction in nitrogen fixation rates was observed; unamended rates of denitrification but not potential denitrification rates (NO₃⁻ added) were depressed after exposure to hydrocarbons.     

Drug-resistant bacteria in Continental Shelf sediments

Fecal indicator bacteria were isolated from water and sediment samples obtained from a sewage sludge disposal site in the Middle Atlantic. Some were found to be resistant to several antimicrobial agents. Isolation of these microbes 30 months after cessation of sludge dumping indicates their survivability in the environment.     

Measurement of rRNA Variations in Natural Communities of Microorganisms on the Southeastern U.S. Continental Shelf

The development of a clear understanding of the physiology of marine prokaryotes is complicated by the difficulties inherent in resolving the activity of various components of natural microbial communities. Application of appropriate molecular biological techniques offers a means of overcoming some of these problems. In this regard, we have used direct probing of bulk RNA purified from selective size fractions to examine variations in the rRNA content of heterotrophic communities and Synechococcus populations on the southeastern U.S. continental shelf. Heterotrophic communities in natural seawater cultures amended with selected substrates were examined. Synechococcus populations were isolated from the water column by differential filtration. The total cellular rRNA content of the target populations was assayed by probing RNA purified from these samples with an oligonucleotide complementing a universally conserved region in the eubacterial 16S rRNA (heterotrophs) or with a 1.5-kbp fragment encoding the Synechococcus sp. strain WH 7803 16S rRNA (cyanobacteria). The analyses revealed that heterotrophic bacteria responded to the addition of glucose and trace nutrients after a 6-h lag period. However, no response was detected after amino acids were added. The cellular rRNA content increased 48-fold before dropping to a value 20 times that detected before nutrients were added. Variations in the rRNA content from Synechococcus spp. followed a distinct diel pattern imposed by the phasing of cell division within the irradiance cycle. The results indicate that careful application of these appropriate molecular biological techniques can be of great use in discerning basic physiological characteristics of selected natural populations and the mechanisms which regulate growth at the subcellular level.     

Drug-resistant bacteria in Continental Shelf sediments.

Fecal indicator bacteria were isolated from water and sediment samples obtained from a sewage sludge disposal site in the Middle Atlantic. Some were found to be resistant to several antimicrobial agents. Isolation of these microbes 30 months after cessation of sludge dumping indicates their survivability in the environment.     

Ecological Distribution of Polychaetous Annelids from the New England Outer Continental Shelf,Georges Bank

Four hundred and eight quantitative grab samples collected during the winter and spring of 1977 from the New England Continental Shelf (Georges Bank) yielded 333 species of polychaetes. Polychaetes comprised 53.8% of the number of all infaunal species, 53% of the density, and 60.5% of the wet weight biomass for all soft-bodied organisms, at least for the winter. Mean number of species and mean density was significantly higher in the spring than in the winter. Mean values of number of species, H', SDN, density, and biomass were associated with various environmental factors. Based on numerical classification (normal and inverse) five polychaete site groups were identified. To a great extent these site groups were molded by major physical, geologic and biologic processes which influence the productivity of this ecologically and economically important area.     

Biological Communities of the South Texas Continental Shelf

A multi-disciplinary study of the south Texas continental shelfin 1975–1977 investigated physical, chemical, geological,and biological characteristics over spatial and temporal scales,and the results are briefly summarized here. Chlorophyll a concentrationsand zooplankton density and biomass showed reductions relatedto distance from shore. These factors also displayed north-southgradients and correlations with surface salinities. Bottom sedimentsgraded seaward from fine sands nearshore to silts and clayson the outer shelf. Coarser sediments were associated with geologicand physical features such as ancestral deltas and wave action.Benthic populations were distributed in relation to sedimenttype, but other features such as depth, bottom water variability/stability,and primary production in the overlying waters were also importantin determining benthic community structure. The study providesa baseline for future process-oriented investigations and environmentalassessments.     

基因工程菌在生物降解中的应用及其发展

在简要阐述基因工程菌构建方法的基础上,系统综述和评价了基因工程构建方法的研究进展及其在生物降解中存在的问题。     

Canada and Arctic Politics: The Continental Shelf Extension

This article challenges the validity of the commonly held assumption that Canada and other Arctic countries are engaged in a highly competitive scramble to stake claims for extensions to their continental shelves beyond 200 nautical miles, and that Canada may lose out because it is lagging behind in this race to claim as many seabed resources as possible. It argues that the process is orderly; that, under international law, Canada already has sovereign rights over the continental shelf beyond 200 nautical miles; that the process is generally characterized by cooperation; and that the timing of various countries’ submissions to the Commission on the Limits of the Continental Shelf will not be a key determinant of success.     

Mapping of the Biological Resources of the Continental Shelf

Distribution patterns of the penaeid shrimp and demersal fishspecies are discussed based upon collections totaling in excessof 330,000 shrimp and 2,245,000 fishes. Depth related zonationreveals nearshore, mid-shelf, outer shelf, and trans-shelf assemblages.Estuary related species are particularly prominent on the northwesternGulf shelf, while rock and reef related species are most importantin the fauna of the eastern Gulf shelf. Recognizable elementsin the shelf fauna also include species of tropical affinity;open ocean and upper slope species; inhabitants of seagrassbeds, mangrove swamps, and carbonate rubble and shell hash;burrowers in soft bottoms; and inhabitants of the upper watercolumn. The eastern Gulf shelf is inhabited by twice as manyfish species and eight times as many unique species as the northwesternshelf, reflecting the great diversity of habitat types in theeastern Gulf. A few key species numerically dominate the ichthyofaunaof the northwestern shelf, but dominance is spread through manyspecies in the east. Seasonal shifts in species density primarilyreflect inshore/offshore seasonal migrations of estuary relatedspecies, but seasonal inshore/offshore density shifts are alsoobserved among the true shelf residents. Trophically the shelfsystems are supported by precipitated plankton and organic detritusderived from rivers, bays and estuaries, seagrass beds, andmangrove swamps, although attached algae are also importantproducers in the east. Mollusks, polychaetes, and small crustaceanswhich feed upon this material, in turn, support the demersalfish communities whose species are generally short-lived. Largerlonglived predators are mostly seasonal migrants which appearin the northern Gulf during the warmer months. Bottom-feedinggeneralists are prominent in the northwest, while specialistsare in great evidence in the east. These distributional studieslay the foundation for understanding the shelf ecological systems,and they also provide a basis for informed management decisions.     

Relation between Candida maltosa Hydrophobicity and Hydrocarbon Biodegradation

Summary The growth of Candida maltosa on hydrocarbons (dodecane and hexadecane) was influenced by adding various natural and synthetic surfactants. Microbial adhesion to the hydrocarbon was used to measure the surface cell hydrophobicity of the yeast, which in the presence of a synthetic surfactant correlated with the degree of hydrocarbon biodegradation. Non-ionic surfactants caused the highest degree of hydrocarbon biodegradation corresponding the lowest hydrophobicity. A different correlation was observed with natural surfactants, of which saponin was the most effective for hydrocarbon biodegradation, though the concentration of this surfactant had no influence on surface cell hydrophobicity.     

Protocols To Enhance Biodegradation of Hydrocarbon Contaminants in Soil

Protocols were developed to determine whether microbial metabolism limits the ultimate removal of contaminants from soil. Two soils were used: a creosote contaminated soil and a soil contaminated with crude oil. A laboratory-scale slurry-phase bioreactor was used to maximize the rate of desorption of components from the soil to the aqueous phase. The protocols to enhance the ultimate removal of hydrocarbons were as follows: stimulation of the bacterial cultures with either naphthalene or a mixture of anthracene and phenanthrene, the use of static conditions to enhance bacterial attachment to the nonaqueous phase liquids in the soil, and increased incubation temperature. Addition of the polycyclic aromatic hydrocarbon (PAH) compounds did not stimulate removal of individual target compounds, classes of compounds or total thermally extractable organics. A comparison of well-mixed and static culture conditions showed equivalent removal, except for the lightest PAH and petroleum fractions that were removed more under well-mixed conditions. Increasing the temperature to 30°C from 21°C gave more rapid initial removal of petroleum components, but the ultimate removal was unaffected. Removal of components from the creosote-contaminated soil was unaffected by temperature. These results suggest that desorption of contaminants from the soils limited the ultimate removal of contaminants, not the biological activity.     

Studies on the Utilization of Hydrocarbon by Microorganisms

An uracil-requiring mutant (KY7122) of Arthrobacter paraffineus KY4303 (ATCC15591) was found to accumulate orotic acid and orotidine on n-paraffine as a sole carbon source.

Both substances were definitely indentified as orotic acid and orotidine, from the results on column and paper chromatography, UV and IR absorption spectra, elementary analysis and analyses of hydrolysate.

Cultural conditions for orotic acid and orotidine fermentation were then investigated. As the carbon source n-paraffines from C₁₄ to C₁₆ were the most suitable for the fermentation, and sorbitol, fructose and mannitol were best utilized for the growth, and orotidine produced from them were twice as much as those from hydrocarbon. The addition of 200 mg of uracil and 2 g of C. S. L to 1 liter of medium was most optimal for orotic acid and orotidine fermentation.

Orotic acid and orotidine accumulations were enhanced by the addition of either l-tyrosine, l-leusine, l-threonine, gluconate or meat extract.     

The Svalbard Continental Shelf Controversy: Legal Disputes and Political Rivalries

Norway's claim to exclusive rights over the continental shelf surrounding the former terra nullius Arctic archipelago of Svalbard is controversial, with the unclear scope of the Svalbard Treaty recognized as “a main challenge” by Norway's parliament. This article explores the nature of this challenge by: (1) giving an account of the legal basis of the conflict; (2) analyzing its political context, and (3) discussing the contemporary judicial and political processes which may or may not resolve the conflict. This article concludes that the issue seems to escape judicial settlement, rendering the controversy a matter of international politics. With the world's eyes increasingly on the petroleum resources of the Arctic, a clarification over the legal status of the Svalbard shelf is not in sight.     

Aerobic and Anaerobic Biodegradation of Aged Pentachlorophenol by Indigenous Microorganisms

Pentachlorophenol (PCP) use as a general biocide, particularly for treating wood, has led to widespread environmental contamination. Biodegradation has emerged as the main mechanism for PCP degradation in soil and groundwater and a key strategy for remediation. Examining the microbial biodegrading potential for PCP at a contaminated site is crucial in determining its fate. Hundreds of studies have been published on PCP microbial degradation, but few have described the biodegradation of PCP that has been in contact with soils for many years. The bioavailability of “aged” hydrophobic organics is a significant concern. PCP- and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)-contaminated soil samples from several depths at a former wood treatment site were placed under varying conditions in the laboratory to determine the anaerobic and aerobic potential for biodegradation of chlorophenols at the site. PCP biodegradation occurred in both anaerobic and aerobic soil samples. Rapid aerobic degradation occurred in samples spiked with 2- and 4-chlorophenol, but not with 3-chlorophenol. Reductive dechlorination of PCP in anaerobic samples resulted in the accumulation of 3-chlorophenol. In most anaerobic replicates, 3-chlorophenol was degraded with the appearance of detectable, but not quantifiable amounts of phenol. These results indicate excellent potential for remediation at the site using the indigenous microorganisms under both aerobic and anaerobic conditions. However, a fraction of the PCP was unavailable for degradation.     

Biodegradation of Halogenated Hydrocarbon Fumigants by Nitrifying Bacteria

Three species of nitrifying bacteria were tested for the ability to degrade the halocarbon fumigants methyl bromide, 1,2-dichloropropane, and 1,2-dibromo-3-chloropropane. The soil nitrifiers Nitrosomonas europaea and Nitrosolobus multiformis degraded all three fumigants, while the marine nitrifier Nitrosococcus oceanus degraded only methyl bromide under the conditions tested. Inhibition of biodegradation by allylthiourea and acetylene, specific inhibitors of ammonia monooxygenase, suggests that ammonia monooxygenase is the enzyme which catalyzes fumigant degradation.     

A Case of Phosphorus Limiting Monoaromatic Hydrocarbon Biodegradation in Groundwater

A funnel-and-gate system has been installed at a natural gas condensate-contaminated field site, for aerobic treatment of contaminated groundwater. Laboratory microcosms were used to assess the ability of indigenous microorganisms to biodegrade monoaromatic hydrocarbons (benzene, toluene, ethylbenzene and isomers of xylene and trimethylbenzene) in the groundwater. Biodegradation was restricted unless phosphorus was added to the site water. Inorganic nitrogen addition had little effect. Estimated zero-order biodegradation rates for benzene, the predominant monoaromatic hydrocarbon in the water, were 87 μj,g/L/d in the absence of added P, but as high as 397 μg/L/d in P-amended microcosms. It was found that finely ground apatite rock could be used as a source of P by the groundwater microbiota, suggesting that this material could serve as a long-term P source in the funnel-and-gate treatment system.     

Effects of Oxygenation on Hydrocarbon Biodegradation in a Hypoxic Environment

In 1984, an underground storage tank leaked approximately 41,000 L of gasoline into the ground water at the Naval Construction Battalion Command in Port Hueneme, CA (USA). Benzene, toluene, ethylbenzene, and xylenes (BTEX) contamination stimulated remedial action. In 1995, a ground water circulation well (GCW) and network of surrounding monitoring wells were installed. After year of operation, dissolved oxygen and nitrate concentrations remained low in all monitoring wells. Benzene utilization (the sum of respiration, uptake, and conversion to polar compounds) ranged from 0.03 to 4.6 µg L^-1 h^-1, and toluene utilization ranged from 0.01 to 5.2 µg L^-1 h^-1. Heterotrophic bacterial productivity (total carbon assimilation) increased dramatically in the GCW, although benzene and toluene utilization decreased markedly relative to surrounding wells. Benzene and toluene uptake accounted for a significant proportion (mean=22%) of the heterotrophic bacterial productivity except within the GCW, indicating other fuel contaminant or indigenous organic carbon and not BTEX compounds served as primary carbon source. The GCW effectively air-stripped BTEX compounds, but failed to stimulate benzene and toluene biodegradation and thus would not be effective for stimulating BTEX bioremediation under current deployment parameters. Air stripping was three orders of magnitude more effective than biodegradation for removing benzene and toluene in the GCW.     

The Outer Continental Shelf of Coastal States and the Common Heritage of Mankind

The establishment of the outer limits of the continental shelf not only involves the rights and interests of coastal states, but also the interests of the international community as a whole. This article examines this balance between coastal states’ assertions of their outer continental shelf limits and the common heritage of mankind.     

Distribution of Aldoxime Dehydratase in Microorganisms

The distribution of phenylacetaldoxime-degrading and pyridine-3-aldoxime-degrading ability was examined with intact cells of 975 microorganisms, including 45 genera of bacteria, 11 genera of actinomyces, 22 genera of yeasts, and 37 genera of fungi, by monitoring the decrease of the aldoximes by high-pressure liquid chromatography. The abilities were found to be widely distributed in bacteria, actinomyces, fungi, and some yeasts: 98 and 107 strains degraded phenylacetaldoxime and pyridine-3-aldoxime, respectively. All of the active strains exhibited not only the aldoxime-dehydration activity to form nitrile but also nitrile-hydrolyzing activity. On the other hand, all of 19 nitrile-degrading microorganisms (13 species, 7 genera) were found to exhibit aldoxime dehydration activity. It is shown that aldoxime dehydratase and nitrile-hydrolyzing activities are widely distributed among 188 aldoxime and 19 nitrile degraders and that the enzymes were induced by aldoximes or nitriles.