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1.
Curr Microbiol ; 77(3): 353-360, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31832838

RESUMO

The secondary metabolites geosmin and 2-methylisoborneol (MIB) are known to taint fish with an undesirable, earthy-muddy taste and odor. In an earlier study on a zero-discharge recirculating aquaculture system (RAS), it was found that geosmin and MIB were removed by microbial communities residing in sludge from the digestion basin of the system. In the present study, 16S amplicon sequencing was used to identify changes in relative abundances of bacterial taxa in geosmin and MIB-enriched crude sludge. The removal of geosmin and MIB by the sludge was accompanied by increased abundances of 12 operational taxonomic units (OTUs). The most prominent increase in abundances was recorded for OTUs affiliated with bacterial genera known to harbor denitrifiers. Among these were the Betaproteobacteria genera Thauera, which utilizes terpenes to fuel denitrification, and Comamonas, which was previously isolated from the digestion basin of the same system and is capable of growth on geosmin and MIB as sole carbon and energy sources. Thus far, denitrification has been associated with bacteria capable of utilizing terpenes other than geosmin and MIB. The significant increase in the abundance of denitrifying bacterial genera in sludge in which geosmin and MIB comprised only 0.06% of the total carbon content might indicate that such bacteria play a major role in the removal of these compounds in anoxic environments.

2.
Chemosphere ; 169: 69-77, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27863304

RESUMO

Off-flavor in fish poses a serious threat for the aquaculture industry. In the present study, removal of 2-methylisoborneol (MIB), an off-flavor causing compound, was found to be mediated by adsorption and bacterial degradation in sludge derived from an aquaculture system. A numerical model was developed which augmented Langmuir equations of kinetics of adsorption/desorption of MIB with first order degradation kinetics. When laboratory-scale reactors, containing sludge from the aquaculture system, were operated in a recirculating mode, MIB in solution was depleted to undetectable levels within 6 days in reactors with untreated sludge, while its depletion was incomplete in reactors with sterilized sludge. When operated in an open flow mode, removal of MIB was significantly faster in reactors with untreated sludge. Efficient MIB removal was evident under various conditions, including ambient MIB levels, flow velocities and sludge loads. When operated in an open flow mode, the model successfully predicted steady MIB removal rates with time. During steady state conditions, most of the MIB removal was found to be due to microbial degradation of the adsorbed MIB. Findings obtained in this study can be used in the design of reactors for removal of off-flavor compounds from recirculating aquaculture systems.


Assuntos
Aquicultura , Poluentes Químicos da Água/análise , Absorção Fisico-Química , Adsorção , Animais , Monitoramento Ambiental , Peixes , Esgotos/microbiologia , Paladar
3.
FEMS Microbiol Ecol ; 89(1): 149-61, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24749684

RESUMO

Standard aquaculture generates large-scale pollution and strains water resources. In aquaculture using zero discharge systems (ZDS), highly efficient fish growth and water recycling are combined. The wastewater stream is directed through compartments in which beneficial microbial activities induced by creating suitable environmental conditions remove biological and chemical pollutants, alleviating both problems. Bacterial predators, preying on bacterial populations in the ZDS, may affect their diversity, composition and functional redundancy, yet in-depth understanding of this phenomenon is lacking. The dynamics of populations belonging to the obligate predators Bdellovibrio and like organisms (BALOs) were analyzed in freshwater and saline ZDS over a 7-month period using QPCR targeting the Bdellovibrionaceae, and the Bacteriovorax and Bacteriolyticum genera in the Bacteriovoracaeae. Both families co-existed in ZDS compartments, constituting 0.13-1.4% of total Bacteria. Relative predator abundance varied according to the environmental conditions prevailing in different compartments, most notably salinity. Strikingly, the Bdellovibrionaceae, hitherto only retrieved from freshwater and soil, also populated the saline system. In addition to the detected BALOs, other potential predators were highly abundant, especially from the Myxococcales. Among the general bacterial population, Flavobacteria, Bacteroidetes, Fusobacteriaceae and unclassified Bacteria dominated a well mixed but seasonally fluctuating diverse community of up to 238 operational taxonomic units, as revealed by 16S rRNA gene sequencing.


Assuntos
Água Doce/microbiologia , Água do Mar/microbiologia , Microbiologia da Água , Animais , Aquicultura , Bacteroidetes/genética , Bdellovibrio/genética , Biodiversidade , Peixes/microbiologia , Flavobacteriaceae/genética , Fusobactérias/genética , Genes Bacterianos , Tipagem Molecular , Filogenia , RNA Ribossômico 16S/genética , Reação em Cadeia da Polimerase em Tempo Real , Estações do Ano , Águas Residuárias/microbiologia
4.
Appl Environ Microbiol ; 78(2): 363-70, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22081577

RESUMO

Using a relatively simple enrichment technique, geosmin and 2-methylisoborneol (MIB)-biodegrading bacteria were isolated from a digestion basin in an aquaculture unit. Comparison of 16S rRNA gene sequences affiliated one of the three isolates with the Gram-positive genus Rhodococcus, while the other two isolates were found to be closely related to the Gram-negative family Comamonadaceae (Variovorax and Comamonas). Growth rates and geosmin and MIB removal rates by the isolates were determined under aerated and nonaerated conditions in mineral medium containing either of the two compounds as the sole carbon and energy source. All isolates exhibited their fastest growth under aerobic conditions, with generation times ranging from 3.1 to 5.7 h, compared to generation times of up to 19.1 h in the nonaerated flasks. Incubation of the isolates with additional carbon sources caused a significant increase in their growth rates, while removal rates of geosmin and MIB were significantly lower than those for incubation with only geosmin or MIB. By fluorescence in situ hybridization, members of the genera Rhodococcus and Comamonas were detected in geosmin- and MIB-enriched sludge from the digestion basin.


Assuntos
/metabolismo , Carbono/metabolismo , Comamonadaceae/isolamento & purificação , Comamonas/isolamento & purificação , Naftóis/metabolismo , Rhodococcus/isolamento & purificação , Análise por Conglomerados , Comamonadaceae/classificação , Comamonadaceae/crescimento & desenvolvimento , Comamonadaceae/metabolismo , Comamonas/classificação , Comamonas/crescimento & desenvolvimento , Comamonas/metabolismo , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Dados de Sequência Molecular , Filogenia , RNA Ribossômico 16S/genética , Rhodococcus/classificação , Rhodococcus/crescimento & desenvolvimento , Rhodococcus/metabolismo , Análise de Sequência de DNA , Microbiologia da Água , Poluentes da Água/metabolismo
5.
Water Res ; 45(7): 2375-82, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21345477

RESUMO

Interest in mariculture systems will rise in the near future due to the decreased ability of the ocean to supply the increasing demand for seafood. We present a trace study using stable carbon and nitrogen isotopes and chemical profiles of a zero-discharge mariculture system stocked with the gilthead seabream (Sparus aurata). Water quality maintenance in the system is based on two biofiltration steps. Firstly, an aerobic treatment step comprising a trickling filter in which ammonia is oxidized to nitrate. Secondly, an anaerobic step comprised of a digestion basin and a fluidized bed reactor where excess organic matter and nitrate are removed. Dissolved inorganic carbon and alkalinity values were higher in the anaerobic loop than in the aerobic loop, in agreement with the main biological processes taking place in the two treatment steps. The δ13C of the dissolved inorganic carbon (δ13C(DIC)) was depleted in 13C in the anaerobic loop as compared to the aerobic loop by 2.5-3‰. This is in agreement with the higher dissolved inorganic carbon concentrations in the anaerobic loop and the low water retention time and the chemolithotrophic activity of the aerobic loop. The δ13C and δ15N of organic matter in the mariculture system indicated that fish fed solely on feed pellets. Compared to feed pellets and particulate organic matter, the sludge in the digestion basin was enriched in 15N while δ13C was not significantly different. This latter finding points to an intensive microbial degradation of the organic matter taking place in the anaerobic treatment step of the system.


Assuntos
Aquicultura/métodos , Ciclo do Carbono , Carbono/análise , Dourada/crescimento & desenvolvimento , Poluentes Químicos da Água/análise , Aerobiose , Amônia/análise , Amônia/metabolismo , Anaerobiose , Animais , Carbono/metabolismo , Isótopos de Carbono/análise , Isótopos de Carbono/metabolismo , Conservação dos Recursos Naturais/métodos , Sulfeto de Hidrogênio/análise , Sulfeto de Hidrogênio/metabolismo , Nitratos/análise , Nitratos/metabolismo , Nitrogênio/análise , Nitrogênio/metabolismo , Isótopos de Nitrogênio/análise , Água do Mar/química , Microbiologia da Água , Poluentes Químicos da Água/metabolismo
6.
FEMS Microbiol Ecol ; 72(3): 476-84, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20402774

RESUMO

The effect of NO(3)(-) addition on dissimilatory SO(4)(2-) reduction and sulfide conversion in organic-rich sludge from the digestion basin of a recirculating marine aquaculture system was studied. SO(4)(2-) reduction could only explain a minor fraction (up to 4-9%) of the observed total sulfide production (up to 35 mmol L(-1) day(-1)), indicating that the main source of sulfide in the sludge was not SO(4)(2-) reduction, but desulfuration during the decomposition of organic matter. Although NO(3)(-) inhibited SO(4)(2-) reduction, but not desulfuration, the primary NO(3)(-) mitigation effect was the onset of NO(3)(-)-mediated sulfide oxidation (up to 75 mmol L(-1) day(-1)), partially to elemental sulfur (S(0)). Above NO(3)(-) concentrations of 0.6 mM in the bulk water, the net sulfide production and oxidation zones were moved deeper into flocs and sludge cores, which effectively prevented sulfide from entering the water column. However, the sulfide efflux from the sludge instantly recovered after NO(3)(-) depletion. Thus, the NO(3)(-) level in the water column controls the zonation and magnitude of sulfur transformations in the sludge. The effect of NO(3)(-) relies therefore on its sustained presence in the water column, which in turn depends on a well-functioning nitrification in the mariculture system.


Assuntos
Aquicultura , Nitratos/metabolismo , Esgotos/química , Sulfatos/metabolismo , Eliminação de Resíduos Líquidos , Sulfetos/metabolismo
7.
Water Res ; 43(2): 474-80, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18986667

RESUMO

In a previous study on a recirculating fish culture system, levels of geosmin and 2-methylisoborneol were found to decrease when culture water was recirculated through the anaerobic sludge digestion treatment stage of the system. This finding led us to the present study in which the geosmin and 2-methylisoborneol removal capacity of the sludge derived from this treatment stage was examined in vitro. It was found that reduction of off-flavor compounds by the sludge was mediated by both chemical/physical sorption and biological degradation. At geosmin and 2-methylisoborneol concentrations within the range of those experienced in fish culture systems, chemical/physical sorption by the sludge was found to account for a 93% reduction in geosmin and a 79% reduction in 2-methylisoborneol from the overlying water within 48h of incubation. Combined with the biological degradation taking place in the sludge, a complete removal of these compounds from the water phase occurred within 9 days of incubation. By means of repeated washing of the geosmin and 2-methylisoborneol contaminate sludge with clean water, relatively small amounts of these compounds were released from the sludge, a possible indication for the fact that absorption, rather than adsorption, underlies the chemical/physical removal process.


Assuntos
Aquicultura/métodos , Naftóis/metabolismo , Esgotos/microbiologia , Aquicultura/instrumentação , Fatores de Tempo , Eliminação de Resíduos Líquidos , Purificação da Água
8.
Water Res ; 42(16): 4386-92, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-18718629

RESUMO

The anaerobic digester is a vital component in a zero-discharge mariculture system as therein most of the organic matter is mineralized and nitrogen-containing compounds are converted to gaseous N(2). Although denitrification is a major respiratory process in this nitrate-rich treatment stage, also sulfate respiration takes place and may cause undesirable high sulfide concentrations in the effluent water. To examine the effect of sulfide on nitrate reduction, in situ depth profiles of inorganic nitrogen and sulfur compounds were determined. Additionally, nitrate reduction was examined as a function of ambient sulfide concentrations in sludge collected from different locations in the anaerobic reactor. Depth profiles showed high concentrations of nitrate and low concentrations of sulfide and ammonia in the aqueous layer of the reactor. A sharp decrease of nitrate and an increase in sulfide and ammonia concentrations was measured at the water-sludge interface. Nitrate reduction was highest in this interface zone with rates of up to 8.05+/-0.57 micromol NO(3)(-)h(-1)g((sludge))(-1). Addition of sulfide increased the nitrate reduction rate at all sludge depths, pointing to the important role of autotrophic denitrification in the anaerobic reactor. Dissimilatory nitrate reduction to ammonia (DNRA) was found to be low in all sludge layers but was enhanced when sludge was incubated at high sulfide concentrations. Although nitrate reduction rates increased as a result of sulfide addition to sludge samples, no differences in nitrate reduction rates were observed between the samples incubated with different initial sulfide concentrations. This as opposed to sulfide oxidation rates, which followed Michaelis-Menten enzymatic kinetics. Partial oxidation of sulfide to elemental sulfur instead of a complete oxidation to sulfate, could explain the observed patterns of nitrate reduction and sulfide oxidation in sludge incubated with different initial sulfide concentrations.


Assuntos
Aquicultura/instrumentação , Nitratos/química , Esgotos/química , Sulfetos/química , Anaerobiose , Reatores Biológicos , Minerais , Nitratos/metabolismo , Nitrogênio/química , Sulfetos/metabolismo
9.
FEMS Microbiol Ecol ; 63(2): 192-204, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18093145

RESUMO

Zero-discharge marine aquaculture systems are an environmentally friendly alternative to conventional aquaculture. In these systems, water is purified and recycled via microbial biofilters. Here, quantitative data on nitrifier community structure of a trickling filter biofilm associated with a recirculating marine aquaculture system are presented. Repeated rounds of the full-cycle rRNA approach were necessary to optimize DNA extraction and the probe set for FISH to obtain a reliable and comprehensive picture of the ammonia-oxidizing community. Analysis of the ammonia monooxygenase gene (amoA) confirmed the results. The most abundant ammonia-oxidizing bacteria (AOB) were members of the Nitrosomonas sp. Nm143-lineage (6.7% of the bacterial biovolume), followed by Nitrosomonas marina-like AOB (2.2% of the bacterial biovolume). Both were outnumbered by nitrite-oxidizing bacteria of the Nitrospira marina-lineage (15.7% of the bacterial biovolume). Although more than eight other nitrifying populations were detected, including Crenarchaeota closely related to the ammonia-oxidizer 'Nitrosopumilus maritimus', their collective abundance was below 1% of the total biofilm volume; their contribution to nitrification in the biofilter is therefore likely to be negligible.


Assuntos
Aquicultura , Bactérias/isolamento & purificação , Biofilmes , Amônia/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , Sequência de Bases , Hibridização in Situ Fluorescente , Dados de Sequência Molecular , Nitritos/metabolismo , Oxirredução , Oxirredutases/genética , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Água do Mar , Análise de Sequência de RNA
10.
Environ Sci Technol ; 41(15): 5571-4, 2007 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-17822134

RESUMO

Oil dispersants, the tool of choice for treating oil spills in tropical marine environments, is potentially harmful to marine life, including reef corals. In a previous study, we found that dispersed oil and oil dispersants are harmful to soft and hard coral species at early life stages. In this broader study, we employed a "nubbin assay" on more than 10 000 coral fragments to evaluate the short- and long-term impacts of dispersed oil fractions (DOFs) from six commercial dispersants, the dispersants and water-soluble-fractions (WSFs) of Egyptian crude oil, on two Indo Pacific branching coral species, Stylophora pistillata and Pocillopora damicornis. Survivorship and growth of nubbins were recorded for up to 50 days following a single, short (24 h) exposure to toxicants in various concentrations. Manufacturer-recommended dispersant concentrations proved to be highly toxic and resulted in mortality for all nubbins. The dispersed oil and the dispersants were significantly more toxic than crude oil WSFs. As corals are particularly susceptible to oil detergents and dispersed oil, the results of these assays rules out the use of any oil dispersant in coral reefs and in their vicinity. The ecotoxicological impacts of the various dispersants on the corals could be rated on a scale from the least to the most harmful agent, as follows: Slickgone > Petrotech > Inipol = Biorieco > Emulgal > Dispolen.


Assuntos
Antozoários/efeitos dos fármacos , Petróleo/toxicidade , Tensoativos/toxicidade , Testes de Toxicidade/métodos , Animais , Soluções , Tensoativos/administração & dosagem , Análise de Sobrevida , Fatores de Tempo
11.
FEMS Microbiol Lett ; 256(1): 22-9, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16487315

RESUMO

In this study, microscopic and molecular microbial analyses were integrated to characterize rapidly developing white filamentous tufts in a fluidized bed reactor used for nitrate removal from a marine recirculating fish culture system. Formation and rapid elongation of the tufts (often exceeding 50 mm day (-1)) was strongly correlated to transient elevated sulfide concentrations (>50 microM) in the reactor. The dominant bacterial constituents of these tufts were filamentous gram-negative bacteria with densely packed intracellular sulfur granules. Using 16S rRNA gene analysis and fluorescence in situ hybridization it was found that these filamentous bacteria represented a novel Thiothrix phylotype closely related (97% sequence identity) to a previously identified Thiothrix strain endogenous to the marine crustacean Urothoe poseidonis. In addition to filamentous morphotypes, rosette-shaped morphotypes of Thiothrix were also detectable within the tufts.


Assuntos
Reatores Biológicos/microbiologia , Resíduos Industriais , Thiothrix/classificação , Thiothrix/crescimento & desenvolvimento , Sequência de Bases , Primers do DNA/química , Sondas de DNA/química , DNA Bacteriano/química , Hibridização in Situ Fluorescente/métodos , Dados de Sequência Molecular , Nitrogênio/metabolismo , Filogenia , RNA Ribossômico 16S/genética , Água do Mar , Análise de Sequência de DNA , Sulfetos/análise , Sulfetos/metabolismo , Thiothrix/química , Thiothrix/genética , Microbiologia da Água
12.
Appl Environ Microbiol ; 71(10): 6134-41, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16204531

RESUMO

Bacteria presumably involved in oxygen- or nitrate-dependent sulfide oxidation in the biofilters of a recirculating marine aquaculture system were identified using a new application of reverse transcription-PCR denaturing gradient gel electrophoresis (DGGE) analysis termed differential-transcription (DT)-DGGE. Biofilter samples were incubated in various concentrations of sulfide or thiosulfate (0 to 5 mM) with either oxygen or nitrate as the sole electron acceptor. Before and after short-term incubations (10 to 20 h), total DNA and RNA were extracted, and a 550-bp fragment of the 16S rRNA genes was PCR amplified either directly or after reverse transcription. DGGE analysis of DNA showed no significant change of the original microbial consortia upon incubation. In contrast, DGGE of cDNA revealed several phylotypes whose relative band intensities markedly increased or decreased in response to certain incubation conditions, indicating enhanced or suppressed rRNA transcription and thus implying metabolic activity under these conditions. Specifically, species of the gammaproteobacterial genus Thiomicrospira and phylotypes related to symbiotic sulfide oxidizers could be linked to oxygen-dependent sulfide oxidation, while members of the Rhodobacteraceae (genera Roseobacter, Rhodobacter, and Rhodobium) were putatively active in anoxic, nitrate-dependent sulfide oxidation. For all these organisms, the physiology of their closest cultured relatives matches their DT-DGGE-inferred function. In addition, higher band intensities following exposure to 5 mM sulfide and nitrate were observed for Thauera-, Hydrogenophaga-, and Dethiosulfovibrio-like phylotypes. For these genera, nitrate-dependent sulfide oxidation has not been documented previously and therefore DT-DGGE might indicate a higher relative tolerance to high sulfide concentrations than that of other community members. We anticipate that DT-DGGE will be of general use in tracing functionally equivalent yet phylogenetically diverse microbial populations in nature.


Assuntos
Aquicultura , Bactérias/classificação , Água do Mar/microbiologia , Sulfetos/metabolismo , Bactérias/genética , Bactérias/metabolismo , Reatores Biológicos , DNA Bacteriano/análise , DNA Bacteriano/isolamento & purificação , Eletroforese/métodos , Dados de Sequência Molecular , Nitratos/metabolismo , Oxirredução , Oxigênio/metabolismo , Filogenia , RNA Bacteriano/análise , RNA Bacteriano/isolamento & purificação , RNA Ribossômico 16S/genética , RNA Ribossômico 16S/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência de DNA
13.
Environ Sci Technol ; 39(6): 1802-10, 2005 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-15819240

RESUMO

In the present work we describe a comprehensive analysis of sulfide oxidation in a fluidized bed reactor (FBR) from an environmentally sustainable, zero-discharge mariculture system. The FBR received oxygen-depleted effluent from a digestion basin (DB) that is responsible for gasification of organic matter and nitrogen. The FBR is a crucial component in this recirculating system because it safeguards the fish from the toxic sulfide produced in the DB. Microscale sulfide oxidation potential and bacterial community composition within FBR biofilms were correlated to biofilter performance by integrating bulk chemical, microsensor (O2, pH, and H2S), and molecular microbial community analyses. The FBR consistently oxidized sulfide during two years of continuous operation, with an estimated average sulfide removal rate of 1.3 g of sulfide-S L(FBR)(-1) d(-1). Maximum sulfide oxidation rates within the FBR biofilms were 0.36 and 0.21 mg of sulfide-S cm(-3) h(-1) in the oxic and anoxic layers, respectively, indicating that both oxygen and nitrate serve as electron acceptors for sulfide oxidation. The estimated anoxic sulfide removal rate, as extrapolated from bench scale, autotrophic, nitrate-amended experiments, was 0.7 g of sulfide-S L(FBR)(-1) d(-1), which is approximately 50% of the total estimated sulfide removal in the FBR. Community composition analyses using denaturing gradient gel electrophoresis (DGGE) of bacterial 16S rRNA gene fragments from FBR samples taken at six-month intervals revealed several sequences that were closely affiliated with sulfide-oxidizing bacteria. These included the denitrifying, sulfide-oxidizing bacteria Thiomicrospira denitrificans, members of the filamentous Thiothrix genus, and sulfide-oxidizing symbionts from the Gammaproteobacteria. In addition, marine Alphaproteobacteria and Bacteroidetes species were present in all of the DGGE profiles examined. DGGE analyses showed significant shifts in the bacterial community composition between profiles over two years of sampling, indicating the presence of a diverse and dynamic microbial community within the functionally stable FBR. The FBR's combined capacity for both oxic and anoxic sulfide oxidation, as indicated by bulk chemical, microsensor, and molecular microbial analyses, gives it significant functional elasticity, which is crucial for proper performance in the dynamic environment of this mariculture system.


Assuntos
Aquicultura , Reatores Biológicos , Sulfetos/metabolismo , Gerenciamento de Resíduos/métodos , Bactérias/crescimento & desenvolvimento , Biofilmes , Sulfeto de Hidrogênio/análise , Concentração de Íons de Hidrogênio , Oxidantes Fotoquímicos/análise , Oxirredução , Oxigênio , Ozônio/análise
14.
Biomol Eng ; 20(4-6): 401-6, 2003 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12919825

RESUMO

While there is an urgent demand to establish reliable ecotoxicological assays for reef corals, there has not been yet an available source material that can supply the high number of colony replicates needed for reliable tests. In past experiments, the major obstacle to obtaining as many fragments as possible had been the damage inflicted to donor colonies by pruning. In this paper, we present the application of coral nubbins, a novel source material for coral ecotoxicology assays. Nubbins from the branching Red Sea coral Stylophora pistillata (n>450) were used for evaluating the impacts of water soluble fractions from a crude oil, an oil dispersant and dispersed oil. Coral nubbins (minute coral fragments in the size of one to several polyps) harvested from a single colony are genetically identical to each other, may be obtained in any quantity needed and whenever research activities demand their use. Several dozens of nubbins can be obtained from a single small branch in branching coral species, a procedure that has minimal impact on donor genotypes. Nubbins production is a low cost procedure and requires limited maintenance space. Results of short and long-term acute ecotoxicological tests are revealed and discussed here, indicating the advantageous use of nubbins as ubiquitous coral material for toxicology assays and physiological studies.


Assuntos
Antozoários/efeitos dos fármacos , Antozoários/crescimento & desenvolvimento , Técnicas Biossensoriais/métodos , Ecossistema , Monitoramento Ambiental/métodos , Petróleo/toxicidade , Testes de Toxicidade/métodos , Poluentes da Água/toxicidade , Animais , Antozoários/metabolismo , Relação Dose-Resposta a Droga , Estudos de Viabilidade , Proteínas de Choque Térmico/metabolismo , Larva/crescimento & desenvolvimento , Análise de Sobrevida , Toxicologia/métodos
15.
Environ Microbiol ; 5(1): 55-63, 2003 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-12542713

RESUMO

Bacterial community structure and physiochemical parameters were examined in a sedimentation basin of a zero-discharge mariculture system. The system consisted of an intensively stocked fish basin from which water was recirculated through two separate treatment loops. Surface water from the basin was pumped over a trickling filter in one loop while bottom-water was recirculated through a sedimentation basin followed by a fluidized bed reactor in the other. Ammonia oxidation to nitrate in the trickling filter and organic matter digestion together with nitrate reduction in the sedimentation basin and fluidized bed reactor, allowed zero-discharge operation of the system. Relatively high concentrations of oxygen, nitrate, sulphate and organic matter detected simultaneously in the digestion basin suggested the potential for a wide range of microbially-mediated transformation processes. In this study, physiochemical parameters were correlated to bacterial diversity and distribution in horizontal and vertical profiles within this basin in an effort to obtain a basic understanding of the chemical and microbial processes in this system. Chemical activity and microbial diversity, the latter measured by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR) amplified 16S rDNA fragments, were higher in the sludge layer than in the overlying aqueous layer of the basin. Chemical parameters in sludge samples close to the basin inlet suggested enhanced microbial activity relative to other sampling areas with evidence of both nitrate and sulphate reduction. Four of the nine DGGE bands identified in this zone were affiliated with the Bacteroidetes phylum. Detected sequences closely related to sequences of organisms involved in the sulphur cycle included Desulfovibrio, Dethiosulfovibrio and apparent sulphur oxidizers from the gamma-proteobacteria. In addition, a number of sequences from the beta and alpha-proteobacteria were identified.


Assuntos
Aquicultura/métodos , Sedimentos Geológicos/microbiologia , Bactérias Gram-Negativas/classificação , Água do Mar/microbiologia , Animais , DNA Bacteriano/análise , DNA Ribossômico/análise , Eletroforese em Gel de Poliacrilamida/métodos , Peixes , Sedimentos Geológicos/química , Bactérias Gram-Negativas/genética , Dados de Sequência Molecular , Nitratos/metabolismo , Consumo de Oxigênio , Filogenia , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Água do Mar/química , Análise de Sequência de DNA , Sulfatos/metabolismo
16.
FEMS Microbiol Lett ; 208(1): 111-6, 2002 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-11934503

RESUMO

Two relatively low-copy plasmids of 9 and 16 kb were found to comprise the extrachromosomal DNA of a Paracoccus strain. Reduction of nitrate by plasmid-cured cells resulted in a significant intermediate nitrite accumulation as compared to wild-type cells. By examining nitrate reduction by transformants containing one of the two plasmids, it was found that nitrite accumulation was influenced by the 9.0-kb plasmid, designated as pYR1. Subcloning analysis showed that a 1.8-kb fragment of this plasmid affected nitrite accumulation. Sequence analysis of this fragment revealed the presence of five open reading frames. One of the six deduced proteins showed a strong homology to ABC transporters.


Assuntos
Nitritos/metabolismo , Paracoccus/metabolismo , Plasmídeos/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Dados de Sequência Molecular , Fases de Leitura Aberta/genética , Oxirredução , Paracoccus/genética , Paracoccus/crescimento & desenvolvimento , Análise de Sequência de DNA , Transformação Bacteriana
17.
Water Res ; 36(4): 825-34, 2002 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-11848352

RESUMO

The potential for iron (hydr)oxides to remove dissolved hydrogen sulphide from seawater has been examined under flow-through conditions. Ferrihydrite (a hydrous iron (III) oxide) was stabilised by precipitation onto zeolite pellets, and rates of sulphide removal were determined under laboratory conditions at pH 8.5. Sulphide removal kinetics were dependent on the initial sulphide concentration, substrate mass and flow rate. The experimental data suggest that these parameters can be optimised to result in the rapid and effective removal of hydrogen sulphide. The results from laboratory experiments compared favourably with sulphide removal kinetics determined in a series of experiments performed online in a recirculating mariculture production system. However, the presence in solution of ligands such as phosphate may also significantly affect reaction rates; a 50% reduction in sulphide removal rate for substrate removed from an online system was partly attributed to phosphate adsorption. The formation of a more crystalline, less reactive iron (hydr)oxide in recharged substrate was the likely result of FeS oxidation, which may also have contributed to the observed reduction in sulphide removal rates. Ferrihydrite-coated zeolite would appear to provide an efficient, low-cost method for sulphide removal, which is particularly suited to relatively small-scale aqueous flow-through systems. The reaction of iron (hydr)oxides with dissolved sulphide is also accompanied by a distinct colour change due to the formation of black FeS(s) which, under appropriate conditions, may be used as a rapid indicator of sulphidic conditions.


Assuntos
Poluentes Atmosféricos/química , Ferritinas/química , Sulfeto de Hidrogênio/química , Poluentes da Água/análise , Purificação da Água/métodos , Precipitação Química , Compostos Férricos , Solubilidade , Movimentos da Água , Poluição da Água/prevenção & controle , Zeolitas/química
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