Inhibitory effect of dissolved organic matter on triplet-induced oxidation of aquatic contaminants.

Excited triplet states of organic chromophores, in particular aromatic ketones, are capable of inducing oxidation of a variety of organic compounds. These reactions probably play an important role in the degradation of organic contaminants in sunlit natural waters. The effect of dissolved natural organic matter (DOM) on the oxidation rate of twenty-two aquatic organic contaminants, including phenols, anilines, phenylurea and s-triazine herbicides, and some pharmaceuticals, was investigated using photoexcited benzophenone-4-carboxylate (CBBP) as the oxidant. For about half of the studied compounds, a decrease in depletion rate was observed in the presence of Suwannee River fulvic acid, used as a reference DOM. Also, depletion rates decreased with increasing DOM concentration, as verified for five selected compounds. Such an inhibitory effect of DOM on oxidation is attributed to its antioxidant properties, whereby oxidation intermediates of the contaminants are supposed to be reduced back to their parent compounds. The presented screening study shows that DOM may be a relevant factor for inhibiting the oxidation of many organic contaminants in surface waters and possibly in engineered water treatment systems.     

Impact of iron-complex (Fe(III)-NTA) on photoinduced degradation of 4-chlorophenol in aqueous solution.

In this research work, the photochemical impact of Fe(III)-nitrilotriacetic acid complex (FeNTA) on the fate of an organic pollutant (4-chlorophenol (4-CP)) was investigated in natural waters. The quantum yields of the photodecomposition of the FeNTA complex and of Fe(II) formation, by an intra-molecular photoredox process (the first stage of the reaction) are high. This photoredox reaction represents the first step of the process leading to 4-CP disappearance. Whereas oxygen does not affect FeNTA photodegradation, 4-CP depletion requires the presence of oxygen. The radical species HO and CO3*- responsible of the degradation were identified by ESR spectroscopy under irradiation. Two different wavelength-dependent mechanisms of 4-chlorophenol degradation are proposed. It clearly appears that under solar irradiation, iron organic complexes like FeNTA can play a significant role on the fate of the organic compounds present in natural waters.     

Evidence of molybdenum association with particulate organic matter under sulfidic conditions

The geochemical behavior of molybdenum (Mo) in the oceans is closely linked to the presence of sulfide species in anoxic environments, where Fe availability may play a key role in the Mo scavenging. Here, we show that Mo(VI) is reduced in the presence of particulate organic matter (represented by sulfate‐reducing bacteria). Molybdenum was immobilized at the surface of both living cells and dead/lysed cells, but not in cell‐free control experiments. Experiments were carried out at four different Mo concentrations (0.1 to 2 mm ) to yield cell‐associated Mo precipitates with little or no Fe, consisting of mainly Mo(IV)‐sulfide compounds with molecular structures similar to Mo enzymes and to those found in natural euxinic sediments. Therefore, we propose that Mo removal in natural sulfidic waters can proceed via a non‐Fe‐assisted pathway that requires particulate organic matter (dead or living sulfate‐reducing bacteria). This pathway has implications for global marine Mo cycling and the current use of Mo‐based proxies for paleo‐environmental investigations.     

Gas chromatography-mass spectrometry with headspace for the analysis of volatile organic compounds in waste water

Headspace analysis combined with high-resolution gas chromatography and detection by mass spectrometry was evaluated for the analysis of 53 volatile organic compounds (VOCs) in river waters, waste waters and treated water samples down to 0.1 microgl(-1) concentration levels. The conditions optimised included sample thermostatting time and temperature, autosampler parameters and the nature of salt, added to the sample. The pollutions origin and their seasonal rippling have been done. It was shown that the content of VOCs in river water mainly correlates to the content of these compounds in waste waters, which shows the anthropogenic character of the pollutions.     

The composition and antianemia efficacy of the iron-containing waters of the Skhodnitsa spring

Slight-mineralized chalybeate waters of the Skhodnitsa deposit containing organic matters are distinguished by high-molecular organic iron complexes present in waters. It is shown that such natural complex iron compounds are characterized by high biological accessibility making these mineral waters very useful for posthemorrhagic anemia due to their therapeutic action.     

Total and hydrolizable particulate organic matter (carbohydrates, proteins and lipids) at a coastal station in Terra Nova Bay (Ross Sea, Antarctica)

We analysed quantity and quality of particulate organic matter during the austral summer 1994/1995 at a coastal station in Terra Nova Bay (Ross Sea, Antarctica). Our main aims were to investigate the origin and biochemical composition of particulate organic matter (POM), to measure its availability for consumers through the study of its digestible fraction (measured by using different enzymes separately) and to highlight the role of hydrolizable compounds in the organic matter diagenesis in the coastal waters at Terra Nova Bay. Temporal and spatial patterns of chlorophyll-a concentrations were reflected by the particulate organic carbon, nitrogen and total biopolymeric carbon concentrations, suggesting that most POM originated directly from phytoplankton. The most evident feature of POM in the coastal waters at Terra Nova Bay was the dominance of proteins (on average 57% of total biopolymeric particulate carbon), followed by carbohydrates (25%) and lipids (18%). We found that about 30% of the refractory particulate organic carbon (assumed to be present only after the complete exploitation of particulate organic nitrogen) did not originate from biopolymeric carbon (as sum of carbohydrate, protein and lipid carbon). This allows us to suggest the use of the digestible fraction of particulate biopolymeric carbon as a more accurate measure of the food availability of POM for consumers. In Terra Nova Bay coastal waters, most of the particulate protein pool was associated with large phytoplankton cells or phytodetritus. As a result, the protein pool appeared less available (i.e. less digestible) than the one present in oligotrophic waters where, conversely, most particulate organic nitrogen is sequestered into bacteria. The relative low availability of the protein pool, together with the rapid sinking of POM and the low remineralization rates of benthic heterotrophic microbes, are suggested as possible factors in determining the “inefficiency” in organic matter recycling of coastal waters at Terra Nova Bay, which behaves as a “loss type” system. Received: 17 June 1997 / Accepted 25 September 1997     

Microbial Communities Involved in Fe Reduction and Mobility During Soil Organic Matter (SOM) Mineralization in Two Contrasted Paddy Soils

Lowland rice fields of West Africa (Ivory Coast) and South Asia (Thailand) are affected by ferrous toxicity or salinity, respectively, and their soil waters contain large amounts of ferrous iron, depending on reducing irrigation condition and suggesting occurrence of bacterial reducing processes. To determine the involvement, dynamic and activities of bacterial communities in Fe(III) reduction and mobilization during anaerobic degradation and mineralization of soil organic matter (SOM), different experiments and analyses have been performed. Results demonstrated that the utilization of SOM as sole carbon, nutrient and energy sources favored the presence of large bacterial communities: facultative anaerobic and anaerobic bacteria, Fe(III)-reducing bacteria (FeRB) (fermentative and Fe respiring), sulfate reducing bacteria (SRB) which are involved in carbon, nitrogen, iron and sulfur cycling. The larger functional diversity is observed in the Ivory Coast paddy soils containing larger amounts of organic matter and sulfur compounds. These communities contained complementary populations (chemoorganotrophic, chemolitotrophic, aerobic, facultative anaerobic and anaerobic) that can be active at different steps of iron solubilization with simultaneous organic matter mineralization. Our results indicate that the pH controlled by bacterial activity, the nature much more than the content of organic matter, and consequently the structure and activity of bacterial communities influence significantly the availability and dynamic of iron in paddy fields which affect the soil quality.     

Metaproteomic analysis of a winter to spring succession in coastal northwest Atlantic Ocean microbial plankton

In this study, we used comparative metaproteomics to investigate the metabolic activity of microbial plankton inhabiting a seasonally hypoxic basin in the Northwest Atlantic Ocean (Bedford Basin). From winter to spring, we observed a seasonal increase in high-affinity membrane transport proteins involved in scavenging of organic substrates; Rhodobacterales transporters were strongly associated with the spring phytoplankton bloom, whereas SAR11 transporters were abundant in the underlying waters. A diverse array of transporters for organic compounds were similar to the SAR324 clade, revealing an active heterotrophic lifestyle in coastal waters. Proteins involved in methanol oxidation (from the OM43 clade) and carbon monoxide (from a wide variety of bacteria) were identified throughout Bedford Basin. Metabolic niche partitioning between the SUP05 and ARCTIC96BD-19 clades, which together comprise the Gamma-proteobacterial sulfur oxidizers group was apparent. ARCTIC96BD-19 proteins involved in the transport of organic compounds indicated that in productive coastal waters this lineage tends toward a heterotrophic metabolism. In contrast, the identification of sulfur oxidation proteins from SUP05 indicated the use of reduced sulfur as an energy source in hypoxic bottom water. We identified an abundance of Marine Group I Thaumarchaeota proteins in the hypoxic deep layer, including proteins for nitrification and carbon fixation. No transporters for organic compounds were detected among the thaumarchaeal proteins, suggesting a reliance on autotrophic carbon assimilation. In summary, our analyses revealed the spatiotemporal structure of numerous metabolic activities in the coastal ocean that are central to carbon, nitrogen and sulfur cycling in the sea.     

Diversity of ammonifying bacteria

The diversity of the micro-organisms, involved in the ammonification in natural waters was examined. The utilization of 41 organic compounds as the sole carbon and energy source was determined for 68 isolated strains. Within this group there was hardly any specificity for the substrate. A single linkage clustering demonstrated that the bacterial population which is able to take up amino acids in natural waters, is composed of a variety of micro-organisms which only slightly differ in their ability to utilize a variety of organic compounds.     

Bacterial consumption of total and dissolved organic carbon in the Great Barrier Reef

Heterotrophic bacteria typically take up directly dissolved organic matter due to the small molecular size, although both particulate and dissolved organic matter have labile (easily consumed) compounds. Tropical coastal waters are important ecosystems because of their high productivity. However, few studies have determined bacterial cycling (i.e. carbon uptake by bacteria and allocation for bacterial biomass and respiration) of dissolved organic carbon in coastal tropical waters, and none has determined bacterial cycling of total and dissolved organic carbon simultaneously. In this study we followed bacterial biomass and production, and organic carbon changes over short-term (12 days) dark incubations with (total organic carbon, TOC) and without particulate organic carbon additions (dissolved organic carbon, DOC). The study was performed at three sites along the middle stretch of the Great Barrier Reef (GBR) during the dry and wet seasons. Our results show that the bacterial growth efficiency is low (0.1–11.5%) compared to other coastal tropical systems, and there were no differences in the carbon cycling between organic matter sources, seasons or locations. Nonetheless, more carbon was consumed in the TOC compared to the DOC incubations, although the proportion allocated to biomass and respiration was similar. This suggests that having more bioavailable substrate in the particulate form did not benefit bacteria. Overall, our study indicates that when comparing the obtained respiration rates with previously measured primary production rates, the GBR is a heterotrophic system. More detailed studies are required to fully explore the mechanisms used by bacteria to cycle TOC and DOC in tropical coastal waters.

     

Bacterial communities in an ultrapure water containing storage tank of a power plant

Ultrapure waters (UPWs) containing low levels of organic and inorganic compounds provide extreme environment. On contrary to that microbes occur in such waters and form biofilms on surfaces, thus may induce corrosion processes in many industrial applications. In our study, refined saltless water (UPW) produced for the boiler of a Hungarian power plant was examined before and after storage (sampling the inlet [TKE] and outlet [TKU] waters of a storage tank) with cultivation and culture independent methods. Our results showed increased CFU and direct cell counts after the storage. Cultivation results showed the dominance of aerobic, chemoorganotrophic α-Proteobacteria in both samples. In case of TKU sample, a more complex bacterial community structure could be detected. The applied molecular method (T-RFLP) indicated the presence of a complex microbial community structure with changes in the taxon composition: while in the inlet water sample (TKE) α-Proteobacteria (Sphingomonas sp., Novosphingobium hassiacum) dominated, in the outlet water sample (TKU) the bacterial community shifted towards the dominance of α-Proteobacteria (Rhodoferax sp., Polynucleobacter sp., Sterolibacter sp.), CFB (Bacteroidetes, formerly Cytophaga-Flavobacterium-Bacteroides group) and Firmicutes. This shift to the direction of fermentative communities suggests that storage could help the development of communities with an increased tendency toward corrosion.     

Simulation of the Viking biology experiments: An overview

Summary Several ground-based investigations have been carried out since the Viking biology results were received from Mars. Many of these have resulted in reasonable simulations of the Martian data, using as analogues of Mars either strong oxidants, UV-treated materials, iron-containing clays, or iron salts. The ambiguity between the GCMS experiment, in which no organic compounds were found on Mars, and the Labeled Release experiment, in which added organics were decomposed, may well be accounted for by these simulations.     

Kinetics and Extent of Mineralization of Organic Chemicals at Trace Levels in Freshwater and Sewage

A sensitive and rapid method was developed to measure the mineralization of ¹⁴C-labeled organic compounds at picogram-per-milliliter or lower levels in samples of natural waters and sewage. Mineralization was considered to be equivalent to the loss of radioactivity from solutions. From 93 to 98% of benzoate, benzylamine, aniline, phenol, and 2,4-dichlorophenoxyacetate at one or more concentrations below 300 ng/ml was mineralized in samples of lake waters and sewage, indicating little or no incorporation of carbon into microbial cells. Assimilation of ¹⁴C by the cells mineralizing benzylamine in lake water was not detected. Mineralization in lake waters was linear with time for aniline at 5.7 pg to 500 ng/ml, benzylamine at 310 ng/ml, phenol at 102 fg to 10 mg/ml, 2,4-dichlorophenoxyacetate at 1.5 pg/ml, and di-(2-ethylhexyl) phthalate at 21 pg to 200 ng/ml, but it was exponential at several p-nitrophenol concentrations. The rate of mineralization of 50 and 500 ng of aniline per ml and 200 pg and 2.0 ng of the phthalate per ml increased with time in lake waters. The phthalate and 2,4-dichlorophenoxyacetate were mineralized in samples from a eutrophic but not an oligotrophic lake. Addition to eutrophic lake water of a benzoate-utilizing bacterium did not increase the rate of benzoate mineralization at 34 and 350 pg/ml but did so at 5 and 50 ng/ml. Glucose and phenol reduced the percentage of p-nitrophenol mineralized at p-nitrophenol concentrations of 200 ng/ml but not at 22.6 pg/ml and inhibited the rates of mineralization at both concentrations. These results show that the kinetics of mineralization, the capacity of the aquatic community to assimilate carbon from the substrate or the extent of assimilation, and the sensitivity of the mineralizing populations to organic compounds are different at trace levels than at higher concentrations of organic compounds.     

Evolutionary trade-offs among decomposers determine responses to nitrogen enrichment

Evolutionary trade-offs among ecological traits are one mechanism that could determine the responses of functional groups of decomposers to global changes such as nitrogen (N) enrichment. We hypothesised that bacteria targeting recalcitrant carbon compounds require relatively high levels of N availability to support the construction costs of requisite extracellular and transport enzymes. Indeed, we found that taxa that used more recalcitrant (i.e. larger and cyclic) carbon compounds were more prevalent in ocean waters with higher nitrate concentrations. Compared to recalcitrant carbon users, labile carbon users targeted more organic N compounds, were found in relatively nitrate-poor waters, and were more common in higher latitude soils, which is consistent with the paradigm that N-limitation is stronger at higher latitudes. Altogether, evolutionary trade-offs may limit recalcitrant carbon users to habitats with higher N availability.     

Genotoxic activity of organic chemicals in drinking water

The information summarized in this review provides substantial evidence for the widespread presence of genotoxins in drinking water. In many, if not most cases, the genotoxic activity can be directly attributed to the chlorination stage of drinking water treatment. The genotoxic activity appears to originate primarily from reactions of chlorine with humic substances in the source waters. Genotoxic activity in drinking water concentrates has been most frequently demonstrated using bacterial mutagenicity tests but results with mammalian cell assay systems are generally consistent with the findings from the bacterial assays. There is currently no evidence for genotoxic damage following in vivo exposures to animals. In some locations genotoxic contaminants of probable industrial and/or agricultural origin occur in the source waters and contribute substantially to the genotoxic activity of finished drinking waters. The method used for sample concentration can have an important bearing on study results. In particular, organic acids account for most of the mutagenicity of chlorinated drinking water, and their recovery from water requires a sample acidification step prior to extraction or XAD resin adsorption. Considerable work has been done to determine the identity of the compounds responsible for the mutagenicity of organic concentrates of drinking water. Recently, one class of acidic compounds, the chlorinated hydroxyfuranones, has been shown to be responsible for a major part of the mutagenic activity. Strategies for drinking water treatment that have been evaluated with respect to reduction of genotoxins in drinking water include granular activated carbon (GAC) filtration, chemical destruction, and the use of alternative means of treatment (i.e., ozone, chlorine dioxide, and monochloramine). GAC treatment has been found to be effective for removal of mutagens from drinking water even after the GAC is beyond its normal use for organic carbon removal. All disinfectant chemicals appear to have the capacity of forming mutagenic chemicals during water treatment. However, the levels of mutagenicity formed with the alternative disinfectants have been generally less than those seen with chlorine and, especially in the case of ozone, highly dependent on the source water.(ABSTRACT TRUNCATED AT 400 WORDS)     

Changes of biomass and bacterial communities in biological activated carbon filters for drinking water treatment

Biological activated carbon (BAC) filtration can usually perform well in removal of biodegradable organic compounds in drinking waters. In this study, a pilot-scale down-flow BAC filtration system was constructed for treatment of ozonated waters. The changes of biomass concentration and bacterial community in the BAC filters with contact time and service time were characterized using phospholipid fatty acid (PLFA) analysis and 16S rRNA gene clone library analysis, respectively. The operational results indicated the BAC filtration system could effectively remove dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Biomass concentration decreased with contact time, but showed only a slight change with service time. Contact time and service time could affect the microbial community structure. Alphaproteobacteria was the largest bacterial group and might have important links with the DOC and AOC removal. This work might provide some new insights into microbial community and biological process in the drinking water biofilters.     

Investigation of the sulfate-reducing bacterial community in the aerobic water and chemocline zone of the Black Sea by the fish technique

Fluorescent in situ hybridization (FISH) was used to analyze the abundance and phylogenetic composition of sulfate-reducing bacteria in the aerobic waters and in the oxic/anoxic transitional zone (chemocline) of the Black Sea, where biogenic formation of reduced sulfur compounds was detected by radioisotope techniques. Numerous sulfate-reducing bacteria of the genera Desulfotomaculum (30.5% of detected bacterial cells), Desulfovibrio (29.6%), and Desulfobacter (6.7%) were revealed in the aerobic zone at a depth of 30 m, while Desulfomicrobium-related bacteria (33.5%) were prevalent in the upper chemocline waters at 150-m depth. Active cells of sulfate-reducing bacteria were much more abundant in the samples collected in summer than in the winter samples from the deep-sea zone. The presence of physiologically active sulfate reducers in oxic and chemocline waters of the Black Sea correlates with the hydrochemical data on the presence of reduced sulfur compounds in the aerobic water column.     

Molecular weight fractionation of dissolved organic matter (DOM) released by phytoplankton

The application of an ultrafiltration procedure for fractionation of molecular weight of dissolved organic matter (DOM) extracellularly released by phytoplankton is described. Seven ultrafiltration membranes Diaflo (Amicon Corp. USA), with range 500--300,000 molecular weight (MW), were used for separation of different molecular weight compounds released by phytoplankton in Rhode River estuary of Chesapeake Bay, and their composition was determined. Percentage of extracellular release of DOM by phytoplankton varied from 3.92--68.07% of total carbon fixed in photosynthesis. The composition of algal extracellular products varied with different phytoplankton populations. However, two fractions of molecular weight compounds dominated in the composition of DOM released, i.e. a low molecular weight fraction of less than 1,000 MW and the fraction between 10,000--30,000 MW. The ultrafiltration procedure is effective for studying the composition of DOM released by phytoplankton in natural waters.     

Habitat Segregation and Biochemical Activities of Marine Members of the Family Vibrionaceae

A comparative study of marine members of the family Vibrionaceae with the technique of numerical taxonomy revealed habitat segregation as well as a cosmopolitan nature of species distribution among the vibrios in different marine environments. The bacterial strains analyzed were isolated from seawater, sediments, phyto- and zooplankton, and fish in the Indian Ocean, the South and East China Sea, and West Pacific Ocean, and coastal areas of Japan. A total of 155 morphological, physiological, and biochemical tests were carried out for each of 405 strains examined. The results showed that most of the large taxonomical clusters which emerged from the computation corresponded to ecological groups which have particular niches. For instance, each group of seawater vibrios inhabited a particular water layer of limited depth range, in spite of the fact that strains of the group were isolated from sampling locations spread over a wide area from the Indian Ocean to Japanese coast. Various vibrio groups showed remarkable differences in their physiological and biochemical activities, and the activities of each group seemed to correspond with its ecological niche. The strains which inhabited surface-water layers grew fast and actively utilized many high-molecular-weight organic compounds and carbohydrates that are derived from fresh, easily degradable organic matter present in the surface waters, whereas the middle- and deep-water vibrios did not decompose most of the high-molecular-weight organic compounds except chitin but, rather, utilized some carbohydrates and organic acids which seemed to be derived from refractory particulate organic matter present in the deeper waters.     

Hydrogenase activity of Rhodopseudomonas capsulata growing on organic media

When Rhodopseudomonas capsulata B10 grows in media with different organic compounds, the hydrogenase activity estimated both by the evolution and uptake of H2 is lowest in cells taken from the middle of the exponential growth phase, and highest in cells from the beginning of the stationary phase. Cells grown in a medium containing malate have a higher hydrogenase activity than those cultivated in a medium with lactate or other compounds (900 and 20 nmoles of H2 per 1 min per 1 mg of protein, respectively). In the experiments with chloramphenicol (10(-5) M), organic compounds (not CO2) were shown to repress hydrogenase synthesis. When the cells were incubated in a medium without an organic substrate or in its presence, the exogenous H2 or H2 evolved as the result of nitrogenase action causes an increase in the activity of hydrogenase.