Lipid biomarkers of shelf sediments from upwelling regions off Namibia, Peru, and Chile

Sediments of upwelling regions off Namibia, Peru, and Chile contain dense populations of large nitrate-storing sulfide-oxidizing bacteria, Thiomargarita, Beggiatoa, and Thioploca. Increased contents of monounsaturated C16 and C18 fatty acids have been found at all stations studied, especially when a high density of sulfide oxidizers in the sediments was observed. The distribution of lipid biomarkers attributed to sulfate reducers (10MeC16:0 fatty acid, ai-C15:0 fatty acid, and mono-O-alkyl glycerol ethers) compared to the distribution of sulfide oxidizers indicate a close association between these bacteria. As a consequence, the distributions of sulfate reducers in sediments of Namibia, Peru, and Chile are closely related to differences in the motility of the various sulfide oxidizers at the three study sites. Depth profiles of mono-O-alkyl glycerol ethers have been found to correlate best with the occurrence of large sulfide-oxidizing bacteria. This suggests a particularly close link between mono-O-alkyl glycerol ether-synthesizing sulfate reducers and sulfide oxidizers. The interaction between sulfide-oxidizing bacteria and sulfate-reducing bacteria reveals intense sulfur cycling and degradation of organic matter in different sediment depths.

Anaerobic methanotrophic archaea-2 and Desulfosarcina/Desulfococcus group in sediments at different stations

The anaerobic oxidation of methane (AOM) with sulfate as terminal electron acceptor is mediated by consortia of methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB). In sediment samples from Hydrate Ridge, the Isis Mud Volcano and the Gulf of Mexico, DSS cells accounted for 3-6% of all DAPI-stained single cells. Out of these, 8-17% were labelled with probe SEEP1a-1441. This translated into relative abundances of single SEEP-SRB1a cells of 0.3% to 0.7%. Contrastingly, in a sediment sample from the Gullfaks oil field, DSS cells accounted for 18% and SEEP-SRB1a for 9% of all single cells. This sediment sample also featured an unusually high abundance of single ANME-2 cells and only very few ANME-2/DSS aggregates in comparison with other AOM habitats. Considering also the nature of the sample, it is likely that the high number of single ANME-2 and SEEP-SRB1a cells were an artifact of sample preparation. Here, harsher sonication was required to remove the microorganisms from coarse sand prior to CARD-FISH analysis.

Degradação anaeróbia de fenol sob diferentes condições nutricionais

A tecnologia anaeróbia tem sido utilizada com sucesso no tratamento de água residuária contendo compostos fenólicos. Recentes pesquisas incluem tais compostos entre aqueles que podem ser degradados através desse processo. O objetivo desse trabalho foi avaliar a degradação do fenol em diferentes condições nutricionais, com ênfase na redução do sulfato. Os experimentos foram realizados com meio de cultura específico para esses microrganismos anaeróbios. Foram realizados ensaios de degradação em reatores em batelada alimentados nas seguintes condições: (1) fenol e sulfato, a diferentes concentrações, com inóculo previamente enriquecido; (2) fenol, sulfato e co-substratos e; (3) fenol, sulfato e extrato de levedura. Todos os ensaios foram realizados em temperatura de 30 graus Celsius, sob agitação de 150 rpm. Foi avaliado o consumo de fenol e sulfato e, produção de metano, em função do tempo, para diferentes concentrações iniciais de fenol e sulfato. Nos ensaios com reatores alimentados com fenol (329,3 mg/l); fenol (307,3 mg/l) e sulfato (160 mg/l); fenol (322.3 mg/l), sulfato (160 mg/l) e lactato (478,16 mg/l); fenol (332,1 mg/l), sulfato (150 mg/l) e etanol (129,76 mg/l), a remoção foi de, respectivamente, 99,8%, 98,2%, 98,8% e 98,8%. Os reatores alimentados com fenol (239,7 mg/l) obtiveram 100% de eficiência na degradação em apenas 11 dias e, os reatores alimentados com fenol (234,3 mg/l) e sulfato (162,5 mg/l) e fenol (256,0 mg/l) e sulfato (500 mg/l) tiveram eficiências de degradação de, respectivamente, 98,8% e 99,3% com 17 dias de operação. Tais eficiências foram obtidas pelo acréscimo de extrato de levedura nos reatores, no início dos ensaios. A caracterização morfológica foi realizada através de microscopia óptica. A diversidade microbiana referente aos Domínios Bacteria e Archaea, além do grupo de bactérias redutoras de sulfato foi avaliada através da técnica de PCR DGGE, onde foram observadas alterações nas populações microbianas, em função das condições nutricionais. Para o Domínio Archaea não foram observadas diferenças nos ensaios realizados. Para o Domínio Bacteria e Grupo das BRS essas diferenças foram, mais facilmente, percebidas com relação ao inóculo e entre os diversos reatores. A alteração na diversidade microbiana pode ter sido decorrente da composição do meio que, nesse caso, foi específico para BRS e a composição do inóculo que continha parte previamente adaptada às BRS. Essas condições adequadas puderam propiciar surgimento e desenvolvimento de populações microbianas capazes de degradar fenol, utilizando sulfato.

Ultrastructure, aggregation-state, and crystal growth of biogenic nanocrystalline sphalerite and wurtzite

In this study, we investigated the size, submicrometer-scale structure, and aggregation state of ZnS formed by sulfate-reducing bacteria (SRB) in a SRB-dominated biofilm growing on degraded wood in cold (Tsimilar to8degreesC), circumneutral-pH (7.2-8.5) waters draining from an abandoned, carbonate-hosted Pb-Zn mine. High-resolution transmission electron microscope (HRTEM) data reveal that the earliest biologically induced precipitates are crystalline ZnS nanoparticles 1-5 nm in diameter. Although most nanocrystals have the sphalerite structure, nanocrystals of wurtzite are also present, consistent with a predicted size dependence for ZnS phase stability. Nearly all the nanocrystals are concentrated into 1-5 mum diameter spheroidal aggregates that display concentric banding patterns indicative of episodic precipitation and flocculation. Abundant disordered stacking sequences and faceted, porous crystal-aggregate morphologies are consistent with aggregation-driven growth of ZnS nanocrystals prior to and/or during spheroid formation. Spheroids are typically coated by organic polymers or associated with microbial cellular surfaces, and are concentrated roughly into layers within the biofilm. Size, shape, structure, degree of crystallinity, and polymer associations will all impact ZnS solubility, aggregation and coarsening behavior, transport in groundwater, and potential for deposition by sedimentation. Results presented here reveal nanometer- to micrometer-scale attributes of biologically induced ZnS formation likely to be relevant to sequestration via bacterial sulfate reduction (BSR) of other potential contaminant metal(loid)s, such as Pb2+, Cd2+, As3+ and Hg2+, into metal sulfides. The results highlight the importance of basic mineralogical information for accurate prediction and monitoring of long-term contaminant metal mobility and bioavailability in natural and constructed bioremediation systems. Our observations also provoke interesting questions regarding the role of size-dependent phase stability in biomineralization and provide new insights into the origin of submicrometer- to millimeter-scale petrographic features observed in low-temperature sedimentary sulfide ore deposits.

Sources of hydrogen sulfide in groundwater on reclaimed land

Fisherman Islands is an area of reclaimed land at the mouth of the Brisbane River in Queensland, Australia. Ongoing groundwater monitoring has found elevated concentrations of hydrogen sulfide (H2S) in the groundwater on the island. The presence of H2S on Fisherman Islands is of concern because of its toxic nature, the potential for acid sulfate soil formation, and its noxious odor. The aim of this study was,to, identify the sources of H2S within the groundwater on Fisherman Islands. It was hypothesized that the H2S is being formed by sulfate reducing bacteria acting on sulfate from seawater, rather than the introduction of sulfide with the dredge sediments. Groundwater and soil samples were collected and analyzed for sulfide, sulfate, and organic carbon contents. Elevated concentrations of sulfides coincide with,elevated concentrations of sulfate in the groundwater and elevated concentrations of organic carbon in the sediments, supporting the hypothesis that sulfide formation is the result of heterotrophic, sulfate reducing organisms.