Heterotrophic Populations Research Articles

Alcanivorax strain detected among the cultured bacterial community from sediments affected by the ‘Prestige’ oil spill

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 362:25-36 (2008) - DOI: https://doi.org/10.3354/meps07431 Alcanivorax strain detected among the cultured bacterial community from sediments affected by the ‘Prestige’ oil spill Jorge Alonso-Gutiérrez1, Maria M. Costa1, Antonio Figueras1, Joan Albaigés2, Marc Viñas3,4, Anna M. Solanas3, Beatriz Novoa1,* 1Instituto de Investigaciones Marinas, CSIC, Eduardo Cabello 6, Vigo 36208, Spain 2IIQAB-CSIC, Jordi Girona 18–26, 08034 Barcelona, Spain 3Department of Microbiology, University of Barcelona, Diagonal 645, 08028 Barcelona, Spain 4GIRO Technological Centre, Rambla Pompeu Fabra, 1, 08100 Mollet del Vallès, Spain *Corresponding author. Email: virus@iim.csic.es ABSTRACT: Sediments sampled next to the Cíes Islands, a natural reserve of the National Park of Atlantic Islands in Ría de Vigo (Spain), 3 mo after the first tide of fuel from the ‘Prestige’ tanker arrived, were chemically and microbiologically characterized. The chemical analysis of the sediments, using oil fingerprinting techniques, showed the occurrence of fresh ‘Prestige’ fuel oil with a background of older hydrocarbon contamination. The cultured bacterial community of the contaminated sediments harbored a high population of total heterotrophs and alkane degraders and a small proportion of aromatic-degrading bacteria. Based on partial 16S ribosomal RNA gene sequence data, 37 different bacterial strains, isolated in diluted marine agar, were detected. Most of them were classified as members of the groups Gammaproteobacteria (59%) and Alphaproteobacteria (21%), although members of the Bacteroidetes (10%) and of Firmicutes (10%) were also found. Some of the different identified bacteria have previously been described as fuel oil–degrading species such as Alcanivorax, Shewanella, Vibrio, Pseudoalteromonas and Marinomonas. Seven independent isolates were able to grow with hexadecane. However, these 7 strains are grouped under the same phylotype, based on the 16S rRNA gene sequence, and were closely related to Alcanivorax borkumensis (Gammaproteobacteria). No aromatic-degrading activities were detected among the culturable bacteria. The presence of fresh fuel without a detected level of biodegradation suggests that Alcanivorax was an early colonizer after the ‘Prestige’ oil spill. To our knowledge, the isolation of Alcanivorax from environmental samples without the aid of an enrichment procedure has not been previously reported. Our results suggest the ability of Alcanivorax to compete and coexist with other heterotrophic marine bacteria in an oil polluted marine environment rich in the nutrients N and P. KEY WORDS:‘Prestige’ oil spill · Alcanivorax · Pollution · Hydrocarbon contamination Full text in pdf format PreviousNextCite this article as: Alonso-Gutiérrez J, Costa MM, Figueras A, Albaigés J, Viñas M, Solanas AM, Novoa B (2008) Alcanivorax strain detected among the cultured bacterial community from sediments affected by the ‘Prestige’ oil spill. Mar Ecol Prog Ser 362:25-36. https://doi.org/10.3354/meps07431 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 362. Online publication date: June 30, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Microcosm experiments of oil degradation by microbial mats. II. The changes in microbial species

The influence of microbial mats on the degradation of two crude oils (Casablanca and Maya) and the effect of oil pollution on the mat structure were assessed using model ecosystems, prepared under laboratory conditions subject to tidal movements, from pristine Ebro Delta microbial-mat ecosystems. Both selected oils are examples of those currently used for commercial purposes. Casablanca crude oil is aliphatic with a low viscosity; Maya represents a sulphur-rich heavy crude oil that is predominantly aromatic. In the unpolluted microcosms, Microcoleus chthonoplastes-, Phormidium- and Oscillatoria-like were the dominant filamentous cyanobacterial morphotypes, whilst Synechoccocus-, Synechocystis- and Gloeocapsa-like were the most abundant unicellular cyanobacteria. After oil contamination, no significant changes of chlorophyll a and protein concentrations were observed, though cyanobacterial diversity shifts were monitored. Among filamentous cyanobacteria, M. chthonoplastes-like morphotype was the most resistant for both oils, unlike the other cyanobacteria, which tolerated Casablanca but not Maya. Unicellular cyanobacteria seemed to be resistant to pollution with both essayed oils, with the exception of the morphotype resembling Gloeocapsa, which was sensitive to both oils. The crude-oil addition also had a significant effect on certain components of the heterotrophic microbial community. Casablanca oil induced an increase in anaerobic heterotrophic bacteria, whereas the opposite effect was observed in those heterotrophs when polluted with Maya oil. The overall results, microbiological and crude-oil transformation analysis, indicate that the indigenous community has a considerable potential to degrade oil components by means of the metabolic cooperation of phototrophic and heterotrophic populations.

Continuous enrichment cultures: insights into prokaryotic diversity and metabolic interactions in deep-sea vent chimneys

The prokaryotic diversity of culturable thermophilic communities of deep-sea hydrothermal chimneys was analysed using a continuous enrichment culture performed in a gas-lift bioreactor, and compared to classical batch enrichment cultures in vials. Cultures were conducted at 60 degrees C and pH 6.5 using a complex medium containing carbohydrates, peptides and sulphur, and inoculated with a sample of a hydrothermal black chimney collected at the Rainbow field, Mid-Atlantic Ridge, at 2,275 m depth. To assess the relevance of both culture methods, bacterial and archaeal diversity was studied using cloning and sequencing, DGGE, and whole-cell hybridisation of 16S rRNA genes. Sequences of heterotrophic microorganisms belonging to the genera Marinitoga, Thermosipho, Caminicella (Bacteria) and Thermococcus (Archaea) were obtained from both batch and continuous enrichment cultures while sequences of the autotrophic bacterial genera Deferribacter and Thermodesulfatator were only detected in the continuous bioreactor culture. It is presumed that over time constant metabolite exchanges will have occurred in the continuous enrichment culture enabling the development of a more diverse prokaryotic community. In particular, CO(2) and H(2) produced by the heterotrophic population would support the growth of autotrophic populations. Therefore, continuous enrichment culture is a useful technique to grow over time environmentally representative microbial communities and obtain insights into prokaryotic species interactions that play a crucial role in deep hydrothermal environments.

Sludge settling and online NAD(P)H fluorescence profiles in wastewater treatment bioreactors operated at low dissolved oxygen concentrations

Biological nitrogen removal via simultaneous nitrification and denitrification (SND) may be achieved in the single-tank bioreactors operated at low dissolved oxygen concentrations (DO). The continuous-stirred tank reactor (CSTR) configuration and the low DO environments employed are; however, more conducive to growth of filamentous bacteria and, thus, poor sludge settling in clarifiers. In this work, a synthetic wastewater was treated in bench-scale (∼6 L) bioreactors under either cyclic or constant-rate aeration, at various sludge retention times (SRT) and DO. The objective was to evaluate the effects of these factors on the sludge settling indicated by sludge volume index. The cyclic aeration was carried out by alternating the aeration between a higher rate for 1 h and a lower (or zero) rate for 30 min. In different experiments, the DO during the period of higher aeration (HDO) was 0.4, 0.6, 0.8, or 2.0 mg/L and the DO during lower aeration (LDO) was 0.0 or 0.2 mg/L. The sludge established under the cyclic aeration was found to settle better than that under constant-rate aeration. Shortening SRT also improved the sludge settling significantly. NAD(P)H fluorescence profiles in these bioreactors were monitored using an online fluorometer. A procedure was developed to quantitatively describe the metabolic state of sludge's heterotrophic population on a 0–1 scale using the fluorescence profile, with “0” corresponding to the fully anoxic-denitrifying state and “1” to the fully aerobic state.

Glucose uptake and extracellular polysaccharides (EPS) produced by bacterioplankton from an eutrophic tropical reservoir (Barra Bonita, SP–Brazil)

We have studied the production of polysaccharides by bacterioplankton in an eutrophic tropical reservoir (Barra Bonita, SP–Brazil) through a decay experiment using glucose as carbon source. The temporal evolution was monitored by measuring the total organic carbon and the contents of monosaccharides. The glucose added to the reservoir sample water was consumed at higher rates within the first hours of incubation, and after 30 days 94.4% of the carbon contents were mineralized; 4.2% remained as particulate organic carbon (POC) form and 1.5% as dissolved organic carbon (DOC) form. The production of polysaccharides occurred in two stages: within the first 48 h, there was intense glucose consumption with small POC increment (ca. 16%) and release of small quantities of dissolved polysaccharide. In the second, more intense stage production was accelerated after the 9th day of incubation, with the highest polysaccharide concentration measured on the 20th day. Such formation of polysaccharides was related to the excretion of capsules and sheaths by bacterioplankton, mainly in the senescence of heterotrophic populations, with release of reserve and structural intracellular materials.

Attempted biofiltration of reduced sulphur compounds from a pulp and paper mill in Northern Sweden

AbstractThe objective of this study was to identify the reduced sulphur compounds (RSCs) present in waste gas from a specific deaerator at a pulp and paper mill in northern Sweden, and to investigate the feasibility of a multi‐stage biofilter to treat these compounds in an industrial setting. Two filter media, rockwool mats and an organic peat and compost mixture, were used as biofilter media. A mixed population of heterotrophs and a strain of Hypomicrobium were examined for DMS and DMDS degradation. Two experimental periods were performed for 45 days each, in the fall and winter in cold climate. Process parameters as well as the number of viable cells of the filter were monitored during operation. Results were inconsistent due to the fluctuations of the system, and a number of operational problems were identified, differing from those developed under controlled, laboratory set‐ups. Process conditions varied greatly, that is, fluctuating temperatures, pollutant concentrations, and airflows that led to insufficient residence times. Both biological and mass transfer limitations are possible explanations for the poor treatment results. This study can contribute to assessing the feasibility of biofilters in the pulp and paper industry, and help reduce the knowledge gap between laboratory studies and field conditions. © 2006 American Institute of Chemical Engineers Environ Prog, 2006

Effect of particulate organic carbon on heterotrophic bacterial populations and nitrification efficiency in biological filters

Competition between heterotrophic and nitrifying bacteria is of major practical importance in aquaculture biofilter design and operation. This competition must be understood to minimize the negative impact of heterotrophic bacteria on an aquaculture system. On the other hand, the heterotrophic population is suspected of having a positive effect against pathogenic bacteria. Little information is available on the bacterial communities present within aquaculture systems, except for nitrifying bacteria, but a combination of traditional aquacultural engineering research methods and novel microbiological techniques offers new opportunities for the study of these communities.The heterotrophic bacterial population activity and the nitrification efficiency of a submerged biological filter were studied for an influent TAN concentration of 2mg/l and varying C/N ratios. The TAN removal rate was found to be 30% lower at a C/N ratio of 0.5 than at a C/N ratio of 0. For higher C/N ratios the reduction in nitrification efficiency was 50% while the attached bacterial abundance was doubled. Moreover, results confirm that abundance of sheared and attached bacteria are correlated. It is not known to what extent biofilter configuration might influence the relationship between heterotrophic and nitrifying bacteria, and further work will be carried out with moving bed and fluidized filters. A better understanding of the role of the heterotrophic bacteria in RAS will help to optimize any positive “biocontrol” effect and to minimize the microbial degradation of rearing water and the reduction of nitrification rates.

Influence of Nutrient Inputs, Hexadecane, and Temporal Variations on Denitrification and Community Composition of River Biofilms

Biofilms were cultivated on polycarbonate strips in rotating annular reactors using South Saskatchewan River water during the fall of 1999 and the fall of 2001, supplemented with carbon (glucose), nitrogen (NH4Cl), phosphorus (KH2PO4), or combined nutrients (CNP), with or without hexadecane, a model compound representing aliphatic hydrocarbons used to simulate a pollutant. In fall 1999 and fall 2001, comparable denitrification activities and catabolic potentials were observed in the biofilms, implying that denitrifying populations showed similar activity patterns and catabolic potentials during the fall from year to year in this river ecosystem, when environmental conditions were similar. Both nirS and nirK denitrification genes were detected by PCR amplification, suggesting that both denitrifying bacterial subpopulations can potentially contribute to total denitrification. Between 91.7 and 99.8% of the consumed N was emitted in the form of N2, suggesting that emission of N2O, a major potent greenhouse gas, by South Saskatchewan River biofilms is low. Denitrification was markedly stimulated by the addition of CNP, and nirS and nirK genes were predominant only in the presence of CNP. In contrast, individual nutrients had no impact on denitrification and on the occurrence of nirS and nirK genes detected by PCR amplification. Similarly, only CNP resulted in significant increases in algal and bacterial biomass relative to control biofilms. Biomass measurements indicated a linkage between autotrophic and heterotrophic populations in the fall 1999 biofilms. Correlation analyses demonstrated a significant relationship (P < or = 0.05) between the denitrification rate and the biomass of algae and heterotrophic bacteria but not cyanobacteria. At the concentration assessed (1 ppb), hexadecane partially inhibited denitrification in both years, slightly more in the fall of 2001. This study suggested that the response of the anaerobic heterotrophic biofilm community may be cyclic and predictable from year to year and that there are interactive effects between nutrients and the contaminant hexadecane.

Microbial degradation of extracellular polysaccharides released by a tropical strain of Staurastrum orbiculare (Zygnematophyceae)

D. Giroldo, A.A.H. Vieira and B.S. Paulsen. 2005. Microbial degradation of extracellular polysaccharides released by a tropical strain of Staurastrum orbiculare (Zygnematophyceae). Phycologia 44: 671–677.The extracellular polysaccharide (EPS) released by a freshwater desmid, Staurastrum orbiculare (Zygnematophyceae), was characterized and their degradation by heterotrophic microbial populations was also evaluated. The EPS was purified by anion exchange column chromatography, the monosaccharide composition was determined by gas chromatography and the linkages of the monosaccharides by gas chromatographic analysis coupled with electron impact mass spectrometry. The EPS was mainly eluted in one weak acid fraction, although a smaller strong acid fraction was also eluted. The two fractions had similar composition and both of them were mainly composed of fucose, glucuronic acid, galactose, galacturonic acid, xylose, glucose, rhamnose and N-acetyl glucosamine. We monitored the entire EPS degradation, and also their components separately, during 35 days using pulse amperometric detection in a high-performance liquid chromatography. Fucose, galactose and especially glucose showed a faster degradation pattern than rhamnose and arabinose, whereas xylose and the total EPS showed an intermediate degradation pattern. The entire EPS was degraded in about 14 days evidencing S. orbiculare EPS as a high quality carbon source to the natural bacterial community of Barra Bonita reservoir.

The coupling of biological iron cycling and mineral weathering during saprolite formation, Luquillo Mountains, Puerto Rico

ABSTRACTCorestones of quartz diorite bedrock in the Rio Icacos watershed in Puerto Rico weather spheroidally to form concentric sets of partially weathered rock layers (referred to here as rindlets) that slowly transform to saprolite. The rindlet zone (0.2–2 m thick) is overlain by saprolite (2–8 m) topped by soil (0.5–1 m). With the objective of understanding interactions between weathering, substrate availability, and resident micro‐organisms, we made geochemical and microbiological measurements as a function of depth in 5 m of regolith (soil + saprolite). We employed direct microscopic counting of total cell densities; enumeration of culturable aerobic heterotrophs; extraction of microbial DNA for yield calculations; and biochemical tests for iron‐oxidizing bacteria. Total cell densities, which ranged from 2.5 × 106 to 1.6 × 1010 g−1 regolith, were higher than 108 g−1 at three depths: in the upper 1 m, at 2.1 m, and between 3.7 and 4.9 m, just above the rindlet zone. High proportions of inactive or unculturable cells were indicated throughout the profile by very low percentages of culturable heterotrophs (0.0004% to 0.02% of total cell densities). The observed increases in total and culturable cells and DNA yields at lower depths were not correlated with organic carbon or total iron but were correlated with moisture and HCl‐extractable iron. Biochemical tests for aerobic iron‐oxidizers were also positive at 0.15–0.6 m, at 2.1–2.4 m, and at 4.9 m depths. To interpret microbial populations within the context of weathering reactions, we developed a model for estimating growth rates of lithoautotrophs and heterotrophs based on measured substrate fluxes. The calculations and observations are consistent with a model wherein electron donor flux driving bacterial growth at the saprolite–bedrock interface is dominated by Fe(II) and where autotrophic iron‐oxidizing bacteria support the heterotrophic population and contribute to bedrock disaggregation and saprolite formation.

Comparative bioremediation of soils contaminated with diesel oil by natural attenuation, biostimulation and bioaugmentation

Bioremediation of diesel oil in soil can occur by natural attenuation, or treated by biostimulation or bioaugmentation. In this study we evaluated all three technologies on the degradation of total petroleum hydrocarbons (TPH) in soil. In addition, the number of diesel-degrading microorganisms present and microbial activity as indexed by the dehydrogenase assay were monitored. Soils contaminated with diesel oil in the field were collected from Long Beach, California, USA and Hong Kong, China. After 12 weeks of incubation, all three treatments showed differing effects on the degradation of light (C 12–C 23) and heavy (C 23–C 40) fractions of TPH in the soil samples. Bioaugmentation of the Long Beach soil showed the greatest degradation in the light (72.7%) and heavy (75.2%) fractions of TPH. Natural attenuation was more effective than biostimulation (addition of nutrients), most notably in the Hong Kong soil. The greatest microbial activity (dehydrogenase activity) was observed with bioaugmentation of the Long Beach soil (3.3-fold) and upon natural attenuation of the Hong Kong sample (4.0-fold). The number of diesel-degrading microorganisms and heterotrophic population was not influenced by the bioremediation treatments. Soil properties and the indigenous soil microbial population affect the degree of biodegradation; hence detailed site specific characterization studies are needed prior to deciding on the proper bioremediation method.

Amplification and attenuation of tetracycline resistance in soil bacteria: aquifer column experiments

A growing inefficacy of antimicrobial agents to treat infectious diseases has stimulated research on the development of antibiotic resistance in bacteria in the environment. Sustained exposure of soil microorganisms to tetracycline (TC) in flow-through columns (50mg/L influent) significantly decreased the effluent concentration of total heterotrophs and selected for TC-resistant (Tetr) soil bacteria. This suggests that TC released to the environment from animal farms may contribute to the development and amplification of TC resistance, with soil bacteria serving as reservoirs for antibiotic resistance continuance. Burkholderia cepacia, with genetic determinants for efflux pumps that facilitate TC excretion, was the only bacterium that grew on TC-amended R2A plates. Following 300 days of exposure, TC was removed from the influent to study the recovery pattern of the microbial community. The percentage of Tetr hererotrophs decreased from 25% to close to the control level of 1% within 1 month of discontinuing TC exposure. This was due both to a significant rebound in the total heterotrophic population and to a significant decrease in the concentration of Tetr bacteria. Thus, discontinuing TC exposure or curtailing its use should enhance natural attenuation mechanisms that mitigate the spread of resistance vectors.

The influence of system complexity on bacterial transport in saturated porous media

A series of miscible-displacement column experiments were conducted under saturated flow conditions to systematically investigate the influence of physical and biological complexity on bacterial activity and fate in the presence and absence of a non-sorbing growth substrate, salicylate. Bacterial elution was monitored for three different systems; System I—a sterilized, inoculated, well-sorted sand, System II—a sterilized, inoculated, heterogeneous loamy sand (Hayhook), and System III—two different unsterilized loamy sands (Hayhook and Vinton) each with their associated indigenous microbial community. Results show that System I behaved ideally with respect to both cell and substrate transport, wherein: (1) growth occurred in response to substrate addition, (2) cell elution increased in response to the substrate pulse, and (3) breakthrough curves were reproducible for both substrate and cell elution. In contrast, System II showed ideal behavior with respect to substrate transport but showed variable behavior for cell transport. Further, there was no measurable growth in response to substrate addition and no increase in cell elution during the salicylate pulse. System III exhibited non-ideal behavior for both substrate and cell transport. Of particular interest is the fact that the indigenous communities of the two soils behaved differently. Specifically, for the Hayhook soil, an increased elution response was observed for the heterotrophic population while the salicylate-degrading community was preferentially retained in the column. In contrast for the Vinton soil, the substrate pulse did not elicit an elution response from either the heterotrophic or salicylate-degrading community from the culturable, indigenous Vinton microorganisms. For Systems II and III, the observed variability appears to be associated with the biological component of the system, since sterile controls were reproducible. This type of systematic study is critical for understanding cell and substrate transport behavior in complex, heterogeneous systems, and illustrates the potential uncertainty associated with measurements in such systems.

Microbial Population and Degradation Activity Changes Monitored During a Chlorinated Solvent Biovent Demonstration

AbstractMicrobial populations and degradation activity increased significantly during a chlorinated solvent bioventing bioremediation effort using propane at Dover Air Force Base in Delaware. The propane injection resulted in degradation of a mixture of chlorinated solvents, including trichloroethylene (TCE), cis‐dichloroethylene (c‐DCE), and 1,1,1‐trichloroethane (TCA). In only 20 d, the propane injection resulted in decreases of TCE and c‐DCE of &gt; 98%, and a decrease in TCA in soil gas by ∼70%. The degradation of the TCA may not have occurred with a methane, butane, toluene, or phenol injection. These decreases in chlorinated solvent concentrations were accompanied by large increases in propane‐utilizing bacteria that ranged from below detection levels prior to the injection to ∼1% of the ending total aerobic heterotrophic population by the end of the propane injection. Thus, a proportional increase occurred as heterotrophic counts increased a hundredfold. Microbial TCE degradation activity, as measured in microcosms, also increased with the propane injection. The highest rates of degradation were observed in microcosms with propane and nutrients, indicating the potential for higher field rates of degradation with nutrient additions.

Respirometric Activities of Heterotrophic and Nitrifying Populations in Aerobic Granules Developed at Different Substrate N/COD Ratios

Aerobic granules were successfully developed at substrate N/COD ratios ranging from 5/100 to 30/100 by weight. By measuring respective respirometric activities of heterotrophic, ammonia-oxidizing, and nitrite-oxidizing bacteria, it was found that the relative abundance of nitrifying bacteria over heterotrophs in aerobic granules was closely related to the substrate N/COD ratios. Results further showed that the populations of both ammonia and nitrite oxidizers were significantly enriched with the increase of the substrate N/COD ratio, while a decreasing trend of heterotrophic population was observed in the aerobic granules. These seem to indicate that high substrate N/COD ratio favors the selection of nitrifying bacteria in the aerobic granules, while the relative activity of nitrifying population against heterotrophic population evolved until a balance between two populations was reached in the aerobic granular sludge community. Moreover, cell elemental composition was correlated with the shift in microbial populations, e.g., the enriched nitrifying population in the aerobic granules resulted in a high cell nitrogen content normalized to cell carbon content. This study provides a good insight into microbial interaction in aerobic granules.

Degradation of 2,4-Dichlorophenoxyacetic Acid (2,4-D) by a Hypersaline Microbial Mat and Related Functional Changes in the Mat Community

Microbial mats possibly possess degradation capacities for haloorganic pollutants because of their wide range of different functional groups of microorganisms combined with extreme diurnal changes in pH, oxygen, and sulfide gradients. In this study, 20 mg/l of the chlorinated herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was applied to a pristine hypersaline cyanobacterial mat from Guerrero Negro, Mexico, under a light regime of 12 h dark/12 h light (600 mumol photons/m(2)s). The loss of 2,4-D was followed by chemical GC analysis; functional changes within the mat were determined with microelectrodes for oxygen, photosynthesis, pH, and sulfide. The depletion of 2,4-D due to photooxidation or sorption processes was checked in control experiments. Within 13 days, the light/dark incubated mats degraded 97% of the herbicide, while in permanent darkness only 35% were degraded. Adsorption of 2,4-D to the mat material, agar, or glass walls was negligible (4.6%), whereas 21% of the herbicide was degraded photochemically. The 2,4-D removal rate in the light/dark incubations was comparable to values reported for soils. The phototrophic community of the mat was permanently inhibited by the 2,4-D addition by 17% on average. The sulfate reduction in the entire mat and the respiration in the photic zone were inhibited more strongly but returned to original levels. Since at the end of the experiment the photosynthetic and respiratory activity of the mats were almost as high as in the beginning and 2,4-D almost completely disappeared, we conclude that the examined mats represent a robust and effective system for the degradation of the herbicide where probably the aerobic heterotrophic population is a major player in the degradation process.

Microbiological Quality and Genotypic Speciation of Heterotrophic Bacteria Isolated from Potable Water Stored in Household Tanks

Abstract Upon storage, a statistically significant increase in heterotrophic plate count (HPC) was detected in samples from household tanks. The most consistent correlate of regrowth was found to be storage time, however, temperature and the microbiological quality of the influent water were also important. Total and fecal coliforms were detected in the influent water and in the household storage tanks. Coliforms growing at 37°C were a small but significant part (about 0.002%) of the total heterotrophic population. In the influent, 92% of the coliforms (11 colony forming units/100 mL) at 44°C were Escherichia coli, while in the household tanks it was 86%. The majority of isolates from the influent and the household tanks recovered on R2A agar formed pigmented colonies and were Gram-negative belonging to the α-, β-, and γ-subclasses of Proteobacteria. Overall, the α-subclass was the dominant type representing 61% of the recovered HPC, and 40 to 50% of the organisms based on 16S rDNA sequence analysis were members of the family Sphingomonadaceae. The presence of E. coli and the isolation of opportunistic pathogens as a significant part of the HPC population from both influent and household tanks indicated a potential health hazard to consumers.

Influence of suspended oyster cultures on nitrogen regeneration in a coastal lagoon (Thau, France)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 276:103-113 (2004) - doi:10.3354/meps276103 Influence of suspended oyster cultures on nitrogen regeneration in a coastal lagoon (Thau, France) Nabila Mazouni* Cépralmar, 20 rue République, 34000 Montpellier, France *Email: mazouni@cepralmar.org ABSTRACT: The present study was designed to quantify the potential influence of oyster cultures (Crassostrea gigas, Thunberg) on dissolved inorganic nitrogen (DIN) renewal in a shallow coastal lagoon (Thau, France), where nitrogen is the factor limiting primary production. The approach was based on a comparative in situ analysis of the seasonal patterns of nitrogenous nutrient exchanges at both the water sediment and oyster cultures water interfaces. The experiments were performed at a station under the influence of oyster cultures (UC) compared with benthic exchanges in a station outside their direct influence (OC) which was used as the reference site for benthic fluxes. In contrast to what it is usually reported for shallow ecosystems, I found evidence of a key influence of suspended oyster culture units (OCU) on the regeneration in the water column of nitrogen available to the phytoplankton, with benthic remineralisation being only of secondary importance. The results also showed that the greatest impact of oyster cultures was on DIN renewal (e.g. nitrogen transformation) in the water column, not on particulate organic nitrogen transfer to the sediment. In the sector studied, it also appeared that nitrogen recycling by both sediments and OCU could satisfy the nitrogen requirements of the primary producers except in summer when other internal nitrogen sources were necessary. Conversely, during most seasons, pelagic primary production could not meet the demand for particulate organic nitrogen of the cultured assemblages (oysters and epibiota). This emphasises the importance to the diet of cultured assemblages of other nitrogen sources such as heterotrophic populations of bacteria, cillates or flagellates. KEY WORDS: Oyster culture · Sediment interface · Nitrogen budget · Fluxes · Lagoon Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 276. Online publication date: August 02, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Bioremediation of soil contaminated by diesel oil

Were evaluated natural attenuation, biostimulation and bioaugmentation on the degradation of total petroleum hydrocarbons (TPH) in soils contaminated with diesel oil. Bioaugmentation showed the greatest degradation in the light (C12 - C23) fractions (72.7%) and heavy (C23 - C40) fractions of TPH (75.2%) and natural attenuation was more effective than biostimulation. The greatest dehydrogenase activity was observed upon bioaugmentation of the Long Beach soil (3.3-fold) and the natural attenuation of the Hong Kong soil sample (4.0-fold). The number of diesel oil degrading microorganisms and heterotrophic population was not influenced by the bioremediation treatments. The best approach for bioremediation of soil contaminated with diesel oil is the inoculum of microorganisms pre-selected from their own environment.

A novel granular sludge sequencing batch reactor for removal of organic and nitrogen from wastewater

Microbial granules were developed at different substrate N/COD ratios in sequencing batch reactors (SBR). Results showed that heterotrophic, nitrifying, and denitrifying populations could peacefully co-exist in microbial granules, while increased substrate N/COD ratio led to significant shifts among three populations in granules. Enhanced activities of nitrifying and denitrifying populations were obtained in microbial granules developed at high substrate N/COD ratios, however, heterotrophic populations in granules tended to decrease with the increase of substrate N/COD ratio. It was found that dissolved oxygen (DO) concentration had a pronounced effect on the efficiency of denitrification by microbial granules, meanwhile the results also indicated that a certain mixing power would be provided to ensure mass transfer between liquid and granules during denitrification. It was demonstrated that complete organics and nitrogen removal can be achieved in single granule-based SBR with high efficiency and stable performance. This is the first study to show the capability of microbial granules in simultaneous removal of organic carbon and nitrogen from wastewater.