RESUMO
In a methanogenic crude oil contaminated aquifer near Bemidji, Minnesota, the decrease in dissolved CH(4) concentrations along the groundwater flow path, along with the positive shift in δ(13) C(CH) (4) and negative shift in δ(13) C(DIC) , is indicative of microbially mediated CH(4) oxidation. Calculations of electron acceptor transport across the water table, through diffusion, recharge, and the entrapment and release of gas bubbles, suggest that these processes can account for at most 15% of the observed total reduced carbon oxidation, including CH(4) . In the anaerobic plume, the characteristic Fe(III)-reducing genus Geobacter was the most abundant of the microbial groups tested, and depletion of labile sediment iron is observed over time, confirming that reduced carbon oxidation coupled to iron reduction is an important process. Electron mass balance calculations suggest that organic carbon sources in the aquifer, BTEX and non-volatile dissolved organic carbon, are insufficient to account for the loss in sediment Fe(III), implying that CH(4) oxidation may also be related to Fe(III) reduction. The results support a hypothesis of Fe(III)-mediated CH(4) oxidation in the contaminated aquifer.
Assuntos
Poluentes Ambientais/metabolismo , Água Subterrânea/microbiologia , Ferro/metabolismo , Metano/metabolismo , Petróleo/microbiologia , Anaerobiose , Biota , Carbono/metabolismo , Isótopos de Carbono/metabolismo , Marcação por Isótopo , Minnesota , Oxirredução , Reação em Cadeia da Polimerase em Tempo RealRESUMO
Data from ice 3590 meters below Vostok Station indicate that the ice was accreted from liquid water associated with Lake Vostok. Microbes were observed at concentrations ranging from 2.8 x 10(3) to 3.6 x 10(4) cells per milliliter; no biological incorporation of selected organic substrates or bicarbonate was detected. Bacterial 16S ribosomal DNA genes revealed low diversity in the gene population. The phylotypes were closely related to extant members of the alpha- and beta-Proteobacteria and the Actinomycetes. Extrapolation of the data from accretion ice to Lake Vostok implies that Lake Vostok may support a microbial population, despite more than 10(6) years of isolation from the atmosphere.
Assuntos
Bactérias/isolamento & purificação , Água Doce/microbiologia , Gelo , Regiões Antárticas , Bactérias/classificação , Bactérias/genética , Fenômenos Fisiológicos Bacterianos , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , DNA Ribossômico/genética , DNA Ribossômico/isolamento & purificação , Água Doce/química , Genes de RNAr , Microscopia Eletrônica de Varredura , Microscopia de Fluorescência , Minerais/análise , Pressão , Proteobactérias/classificação , Proteobactérias/genética , Proteobactérias/isolamento & purificação , Proteobactérias/fisiologia , RNA Ribossômico 16S/genética , Temperatura , Microbiologia da ÁguaRESUMO
By use of the polymerase chain reaction and degenerate oligonucleotide primers for highly conserved regions of nifH, a segment of nifH DNA was amplified from several aquatic microorganisms, including an N2-fixing bacterium closely associated with the marine filamentous cyanobacterium Trichodesmium sp., a heterotrophic isolate from the root/rhizome of the seagrass Ruppia maritima, and the heterocystous freshwater cyanobacterium Anabaena oscillarioides. nifH segments were amplified directly from DNA extracted from the rhizosphere of roots of the seagrass Halodule wrightii. The nifH fragments were then cloned and sequenced. The DNA and deduced amino acid sequences were compared with known sequences, revealing distinct differences between taxonomic groups. This technique was shown to be useful for (i) the detection of N2-fixing microorganisms and (ii) rapidly obtaining the DNA sequence of the nifH gene, which provides information about general taxonomic groups of N2-fixing microorganisms.
Assuntos
Anabaena/genética , Genes Bacterianos , Klebsiella/genética , Fixação de Nitrogênio/genética , Plantas/microbiologia , Microbiologia da Água , Sequência de Aminoácidos , Anabaena/química , Sequência de Bases , Clonagem Molecular , DNA Bacteriano/química , Klebsiella/química , Dados de Sequência Molecular , Plantas/química , Plantas/genética , Reação em Cadeia da PolimeraseRESUMO
C57BL/6 mice were immunized against Leishmania donovani infection with a subcutaneous vaccination protocol. Groups received 3 injections at 4-day intervals combining glucan and killed promastigotes harvested from either logarithmic or stationary phase cultures. Controls were immunized with glucan alone, stationary or log phase promastigotes alone, or were untreated. All groups were challenged intravenously with stationary phase promastigotes at day 45 post-immunization. Results revealed that animals immunized with the glucan-killed parasite vaccine, utilizing promastigotes derived from either log (GPL) or stationary phase cultures (GPS), demonstrated significant resistance against infection as compared to controls or untreated mice. Additionally, the reduction in hepatic amastigote proliferation in mice immunized with GPS was significantly greater than in mice immunized with GPL.
