Libraries of 16S rRNA genes cloned from methanogenic oil degrading microcosms amended with North Sea crude oil and inoculated with estuarine sediment indicated that bacteria from the genera Smithella (Deltaproteobacteria, Syntrophaceace) and Marinobacter sp. (Gammaproteobacteria) were enriched during degradation. Growth yields and doubling times (36 days for both Smithella and Marinobacter) were determined using qPCR and quantitative data on alkanes, which were the predominant hydrocarbons degraded. The growth yield of the Smithella sp. [0.020 g(cell-C)/g(alkane-C)], assuming it utilized all alkanes removed was consistent with yields of bacteria that degrade hydrocarbons and other organic compounds in methanogenic consortia. Over 450 days of incubation predominance and exponential growth of Smithella was coincident with alkane removal and exponential accumulation of methane. This growth is consistent with Smithella's occurrence in near surface anoxic hydrocarbon degrading systems and their complete oxidation of crude oil alkanes to acetate and/or hydrogen in syntrophic partnership with methanogens in such systems. The calculated growth yield of the Marinobacter sp., assuming it grew on alkanes, was [0.0005 g(cell-C)/g(alkane-C)] suggesting that it played a minor role in alkane degradation. The dominant methanogens were hydrogenotrophs (Methanocalculus spp. from the Methanomicrobiales). Enrichment of hydrogen-oxidizing methanogens relative to acetoclastic methanogens was consistent with syntrophic acetate oxidation measured in methanogenic crude oil degrading enrichment cultures. qPCR of the Methanomicrobiales indicated growth characteristics consistent with measured rates of methane production and growth in partnership with Smithella.

Aims: To isolate, select, identify and assess the potential for the biodegradation of synthetic pyrethroids (SPs) in sheep dips. Methods and Results: SP‐degrading bacteria were isolated from a mixed soil sample consisting of garden soil and soils from farms where SPs had been used. The two largest in size were then identified using microscopy, biochemical and genetic techniques to be members of the genera Pseudomonas and Serratia. By comparing the 16S rRNA gene sequences, the Pseudomonas sp. discovered was shown to group within the Pseudomonas fluorescens intrageneric cluster. The Serratia isolated was closely related to Serratia plymuthica. Cell growth and degradation was greatest in the Pseudomonas sp. culture where there was breakdown of 60 mg l−1 to 6 mg l−1 technical cypermethrin in 20 days. Tolerance to the SPs was greater in the Pseudomonas sp. but was found to depend on the availability of other carbon sources and nutrients. Conclusions: The bacteria characterized show the potential to be used in a bioremediation application for the treatment of SP residues. Significance and Impact of the Study: The SP‐degrading bacteria may have use in the disposal of used SP residues and with further research could lead to an alternative route of disposal for use in agriculture or industry.

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Aims:  To investigate the effects of aeration on the ex situ biodegradation of polycyclic aromatic hydrocarbons (PAHs) in creosote‐contaminated soil and its effect on the microbial community present. Methods and Results:  Aerated and nonaerated microcosms of soil excavated from a former timber treatment yard were maintained and sampled for PAH concentration and microbial community changes by terminal restriction fragment length polymorphism (TRFLP) analysis. After an experimental period of just 13 days, degradation was observed with all the PAHs monitored. Abiotic controls showed no loss of PAH. Results unexpectedly showed greater loss of the higher molecular weight PAHs in the nonaerated control. This may have been due to the soil excavation causing initial decompaction and aeration and the resulting changes caused in the microbial community composition, indicated by TRFLP analysis showing several ribotypes greatly increasing in relative abundance. Similar changes in both microcosms were observed but with several possible key differences. The species of micro‐organisms putatively identified included Bacilli, pseudomonad, aeromonad, Vibrio and Clostridia species. Conclusions:  Excavation of the contaminated soil leads to decompaction, aeration and increased nutrient availability, which in turn allow microbial biodegradation of the PAHs and a change in the microbial community structure. Significance and Impact of the Study:  Understanding the changes occurring in the microbial community during biodegradation of all PAHs is essential for the development of improved site remediation protocols. TRFLP allows useful monitoring of the total microbial community.

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