Secondary metabolite gene expression and interplay of bacterial functions in a tropical freshwater cyanobacterial bloom

Cyanobacterial harmful algal blooms (cyanoHABs) appear to be increasing in frequency on a global scale. The Cyanobacteria in blooms can produce toxic secondary metabolites that make freshwater dangerous for drinking and recreation. To characterize microbial activities in a cyanoHAB, transcripts from a eutrophic freshwater reservoir in Singapore were sequenced for six samples collected over one day-night period. Transcripts from the Cyanobacterium Microcystis dominated all samples and were accompanied by at least 533 genera primarily from the Cyanobacteria, Proteobacteria, Bacteroidetes and Actinobacteria. Within the Microcystis population, abundant transcripts were from genes for buoyancy, photosynthesis and synthesis of the toxin microviridin, suggesting that these are necessary for competitive dominance in the Reservoir. During the day, Microcystis transcripts were enriched in photosynthesis and energy metabolism while at night enriched pathways included DNA replication and repair and toxin biosynthesis. Microcystis was the dominant source of transcripts from polyketide and non-ribosomal peptide synthase (PKS and NRPS, respectively) gene clusters. Unexpectedly, expression of all PKS/NRPS gene clusters, including for the toxins microcystin and aeruginosin, occurred throughout the day-night cycle. The most highly expressed PKS/NRPS gene cluster from Microcystis is not associated with any known product. The four most abundant phyla in the reservoir were enriched in different functions, including photosynthesis (Cyanobacteria), breakdown of complex organic molecules (Proteobacteria), glycan metabolism (Bacteroidetes) and breakdown of plant carbohydrates, such as cellobiose (Actinobacteria). These results provide the first estimate of secondary metabolite gene expression, functional partitioning and functional interplay in a freshwater cyanoHAB.Singapore. National Research Foundation (Singapore MIT Alliance for Research and Technology (SMART), Center for Environmental Sensing and Modeling (CENSAM) research program)National Science Foundation (U.S.) (Postdoctoral Research Fellowship in Biology, Grant No. DBI-1202865)National Institute of Environmental Health Sciences (NIEHS Grant P30-ES002109 to the MIT Center for Environmental Health Sciences)MIT International Science and Technology Initiatives (MISTI-Hayashi fund

Ecological recovery of thermically cleaned soil.

Abstract niet beschikbaarMany contaminated sites in the Netherlands are rigorously cleaned-up by excavation of the hazardous soil and subsequently thermal treatment for destruction of the contaminants. This results in a complete dead product. When the soil is redeposited it has to be recolonized by organisms. To assess the possibilities of ecological recovery of these soils, a field experiment in a grassland was performed during one year in 42 enclosures of 60 cm diameter each. They consisted of a core of the unpolluted grassland soil with the natural micro- and meso- organisms, placed in thermically cleaned soil. Eighteen enclosures were fertilized. Six controls contained no core, but only unpolluted soil or cleaned soil. The colonization by nematodes, other mesofauna, bacteria and vegetation as well as some abiotic parameters were studied. After 100 days the cores contained thousands of nematodes/100 gr dry soil, the fertilized cleaned soil hundreds/100 gr and the unfertilized cleaned soil dozens/100 gr. These quantities did not change during the rest of the experiment. The control with cleaned soil without core contained after one year also dozens of nematodes/100 gr. Because in the cleaned soil plant growth was poor, energy input in the soil was hardly present. After identification, nematodes were classified into functional groups and diversity was measured. It was concluded that 1) Rhabditidae were the first nematodes to colonize the cleaned soil (bacteria-feeding r-strategists) ; 2) nematode species present in the cleaned soil were also found in the core ; 3) wind was an important vector in nematode dispersion ; 4) additions of fertilizer stimulated colonization by nematodes. Thermically cleaned soil is not a good habitat for organisms unless soil is improved with nutrients, organic matter and N-fixing vegetation.DGM/DWB-B / Robberse J

Effects of cyanobacteria (blue-green algae) on human health in recreational use of water

Het rapport omvat een literatuurstudie over de mogelijhkheid van vergiftigingen van waterrecreanten aangevuld met resultaten van niet eerder gepubliceerd Nederlands onderzoek. Tevens wordt een beknopt overzicht gegeven over de ecologie van waterbloei veroorzakende cyanobacterien ; de structuur, eigenschappen en isolatie van de toxinen van cyanobacterien ; resultaten van dierexperimenten ; en de ziektebeelden bij de mens. In de bijlagen worden voederproeven met cyanobacterien uit Nederlandse oppervlaktewateren bij muizen en ratten behandeld evenals een methode voor de isolatie van toxinen.Abstract not availableDGMH/BWS-

Influence of in situ extractive soil clean up in Soestduinen on the biological availability of cadmium

Abstract niet beschikbaarSoil contaminated with cadmium was cleaned up in-situ by a HCl extraction technique. The clean-up method reduced the cadmium concentration below A-value. To study ecological risks bioassays were performed with an earthworm (Eisenia andrei) and lettuce (Lactuca sativa) in cleaned up soil as well as in contaminated soil. Both organisms were not able to survive in these soils, unless they were mixed with 25-75% quartzsand. Plants and worms were grown for 28 days. At the start and at the end of the experiments soils, plants and worms were analysed for cadmium. It appeared that the clean up method increased the bioavailability of the cadmium.DGM/DWB-B / Robberse

Ecological recovery of oil contaminated soil during the clean-up with a microbiological restoration technique

Abstract niet beschikbaarTo improve clean-up techniques by landfarming, lysimeters (4.25*4.25*0.5m) were filled with an oil contaminated sandy soil obtained from a bus garage site. Soil (in the open air or covered) was manipulated by raining, fertilizing and seeding. In the half year observation period the impact of restoration techniques on nematode fauna was investigated. The lysimeter results were compared with the composition of nematode fauna in the polluted and in the clean reference soil at the garage site. The numbers of nematodes in the polluted soil were 20 times that of the reference soil, and were dominated by Cuticulariaoxycerca. In the lysimeters bacterial feeders were also dominant at the start, but decreased with time while carnivorous Odontopharynx longicaudata increased. At the end of the experiment restoration of nematode fauna was still in progress: species diversity was 3 times lower than in the reference and feeding group ratio's were quite different.DGM/DWB-B Robberse

Effects of chlorophenols on free-living soil nematodes

Het rapport beschrijft een onderzoek naar de effecten van een geringe, maar langdurige, belasting van chloorfenolen op de aantallen en soortensamenstelling van vrijlevende bodemnematoden. Het onderzoek is uitgevoerd in 5 roestvaste kolommen (lengte 140 cm, diameter 20 cm), ieder gevuld met grond uit hetzij Kootwijk, Rolde, Holten of Maasdijk. Zij werden 7 maanden beregend met een mengsel van chloorfenolen. Aan het begin en aan het eind van de proef werden nematoden kwantitatief en kwalitatief geanalyseerd en in voedselgroepen verdeeld. De chloorfenolen bleken in de bovenste paar centimeter afgebroken te worden. Alleen in deze laag trad een verandering op in de normale verhoudingen tussen de voedselgroepen: de bacterie-etende nematoden werden dominant. Geconcludeerd wordt dat deze groep beschouwd kan worden als indicator voor bodemverontreinigingen met organische stoffen.Abstract not availableDGM/DWB-B /Robberse J

An ecologial classification of the dutch soil based on free-living nematodes

In het rapport wordt een aanzet gegeven tot een typologie van de Nederlandse bodem op basis van de vrijlevende nematodenfauna. De bovenste 10 cm van de minerale bodem van 46 locaties van elkaar verschillend in vegetatie/bodemcombinatie, werden bemonsterd in sept. 1985. De nematoden uit deze monsters werden gekwantificeerd en op naam gebracht. De volgende bodemanalyses werden uitgevoerd: TOC, pH, textuur, kalk, CEC, K, Ca, Mg, basebezetting, N totaal, P totaal, vochtgehalte, porositeit. Het vegetatietype op de locaties werd genoteerd. Van de 46 locaties werden 8 eenmaal per kwartaal bemonsterd om na te gaan in hoeverre de seizoenen invloed hebben op de classificatie. Door middel van het clusteren van monsterpunten is een typologie op grond van nematodendsoorten en milieukenmerken ontworpen. Opgenomen zijn tabellen met: maturity-index, nematoden gerangschikt per type, uniciteit van de monsterpunten, ecosysteemparameters per cluster, relatie tussen nematodensoorten en milieuvariabelen, presentie soorten t.o.v. grondsoort, vochttoestand en vegetatie, fysisch/ chemische analyses, samenstelling nematodenfauna in humus en strooisellaag, inventarisatie nematodenfauna 46 locaties.Abstract not availableDGM/DWB-B /Vegter JJ Robberse J

Chemical-physical and topographical description of the sites of the project "Assessment of biological quality of soils"

Abstract niet beschikbaarNematode fauna used as an instrument for assessing biological quality of soils. A joint study of the Department of Nematology, Agricultural University, Wageningen (biotic parametes). To assess the quality of soils an ecological typology based on the free-living nematode fauna is in development. Herefore knowledge on the relationship between the presence of nematodes and the physical and chemical soil parameters is essential. Fifteen different forest ecosystems spread on 30 locations were sampled between 4/4/88 and 26/5/88. This sampling program covered all the sandy soils of the Netherlands. In 71 samples were analysed: water content ; pH, texture, organic matter, nitrate, ammonium, total nitrogen, sodium, calcium, potassium, magnesium, base capacity and CEC. The analysis of the biotic parameters and the interpretation of the data will be published in another paper.DGM/DWB-B Robberse J