Changes in nitrification and bacterial community structure upon cross-inoculation of Scots pine forest soils with different initial nitrification rates

Nitrification occurs slowly in many acid Scots pine forest soils. We examined if bacterial community structure and interactions between members of the bacterial community in these forest soils prohibit growth of ammonia-oxidising microorganisms and their nitrifying activity. Native and gamma-irradiated Scots pine forest soils known to have low net nitrification rates were augmented with fresh soils or soil slurries from nitrifying Scots pine forest soil, and vice versa. Augmentation of native non-nitrifying soils with nitrifying soils induced net nitrification, although no significant changes in bacterial community structure, as measured by 16S rRNA gene-based denaturing gradient gel electrophoresis (DGGE), were observed. In sterilised soils, the inoculum, i.e. native nitrifying soil or non-nitrifying soil, determined the occurrence of net nitrification and bacterial community structure, and not the origin of the sterilised soils. Our results demonstrate that low net nitrification rates in acid Scots pine forest soils cannot be (solely) explained by unfavourable abiotic soil conditions, but that still uncaptured biotic factors contribute to suppression of nitrification.     

生物强化在厌氧发酵过程中的应用进展

从生物强化作用机理、作用效果及影响因素等方面对国内外生物强化在沼气发酵过程中的研究进行了归纳与总结,表明生物强化在厌氧发酵的原料预处理、系统启动、产气等方面均具有促进作用,可提高系统的产气效率,但多数研究为实验室规模的批式发酵,生物强化的功能菌在发酵系统中的适应能力及稳定性是限制该技术实际应用的关键问题,需揭示投加的功能菌与系统土著微生物间的相互作用机制,研制性能稳定、适应性强的功能菌剂,寻求更佳的生物强化作用方式、建立强化效果的评价标准,才能使生物强化技术在实际工程中得到广泛应用。     

Prospects of Miscanthus x giganteus for PAH phytoremediation: A microcosm study

Phytoremediation of large surface areas using crop cultivation appears as an attractive strategy to allow for long-term but economically viable site rehabilitation programs. The contribution of Miscanthus x giganteus root exudates to the biostimulation of PAH degradation was recently demonstrated using in vitro assays. The aim of this work was to characterize the phytoremediation potential of this perennial grass in the situation of PAH polluted soils. For this purpose, three factors affecting bioremediation, namely the nature of soil organic contaminants (spiked phenanthrene and pyrene each at 100 mg/kg dry soil), bioaugmentation (with a PAH-degrading microflora) and planting (with Miscanthus x giganteus), were arranged according to a full factorial design in pot experiments. Effects of each factor (alone or in combination) were assessed on soil bacterial communities (total culturable bacteria and PAH-degrader enumerations, 16S rDNA molecular diversity analysis) and PAH dissipation. Results showed that contamination was the main factor positively influencing the development of degrader populations. Phenanthrene dissipation was observed regardless the presence of plants or initial PAH-degrading bacterial inoculum whereas significant decreases in pyrene contents were positively influenced by bioaugmentation and to a lesser extent by planting. The ability of plants to maintain a degrading rhizosphere microflora thus enhancing the dissipation of recalcitrant compounds in polluted soils would deserve further investigations.     

Bioaugmentation in the growth and water quality of livebearing ornamental fishes

Bacillus subtilis isolated from the intestine of Cirrhinus mrigala (Hamilton) was incorporated into the rearing water of Poecilia reticulata (Peters), Poecilia sphenops (Valenciennes), Xiphophorus helleri (Heckel) and Xiphophorus maculatus (Gunther) at four different concentrations (5 × 10⁸ cells ml⁻¹, 5 × 10⁷ cells ml⁻¹, 5 × 10⁶ cells ml⁻¹ and 5 × 10⁵ cells ml⁻¹) and its effect on fish growth performance and survival, water quality parameters and bacterial population of water were assessed. The results showed that the addition of bacterial cells in the rearing water resulted in greater survival and a faster growth rate and, hence, greater length and weight increments of the livebearers. The use of a bioaugmentor in the rearing water of the livebearing fishes resulted in significantly lower (P < 0.05) concentrations of dissolved organic matter and total ammonium nitrogen. The counts of motile aeromonads and total coliforms recorded in the water of bioaugmented tanks were also lower than that in the control tank. Bioaugmentation between 10⁶ and 10⁸ cells ml⁻¹ in the rearing water is sufficient in establishing a bioaugmentor and the use of a higher concentration of bacterial cells did not always lead to significantly better results.     

Bioaugmentation of butane-utilizing microorganisms for the in situ cometabolic treatment of 1,1-dichloroethene, 1,1-dichloroethane, and 1,1,1-trichloroethane

Bioaugmentation of microbial cultures is a potential method to enhance the performance of in situ bioremediation. In this study we evaluated the bioaugmentation of aerobic microorganisms that grow on butane that can transform chlorinated aliphatic hydrocarbon (CAH) mixtures, such as 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichhloroethane (1,1-DCA) and 1,1-dichloroethene (1,1-DCE). This mixture of contaminants is of interest, since 1,1,1-TCA was a frequently used solvent at Department of Defense (DoD) facilities in the United States, and 1,1-DCE and 1,1-DCA are abiotic and biotic transformation products of 1,1,1-TCA. Kinetic studies with butane grown enrichment cultures and pure cultures isolated from the enrichment culture showed effective transformation of mixtures of these contaminants, with 1,1-DCE most rapidly transformed, followed by 1,1-DCA, and 1,1,1-TCA. In laboratory microcosm batch experiments, with aquifer material and groundwater from the field site, microcosms bioaugmented with mixed and pure cultures outperformed microcosms where indigenous butane-utilizing microorganisms were stimulated. The microcosm tests were consistent with the kinetics from mixed and pure cultures. Field studies were conducted in the saturated zone at the Moffett Field In Situ Test Facility in California. Tests were performed in an indigenous test leg along with a bioaugmented test leg, and the bioaugmented test leg outperformed the indigenous test leg. In the bioaugmented leg, 1,1-DCE was more effectively transformed, followed by 1,1-DCA, and 1,1,1-TCA, consistent with the results from laboratory kinetic studies and microcosm studies.     

生物强化技术在污水处理中的作用机理及应用现状

针对如今传统生物处理方法处理难降解、有毒废水能力不足问题,提出了用生物强化技术处理这一类废水.介绍了生物强化技术的机理、高效菌的获取手段及技术的优势,并进一步阐述了生物强化技术未来的研究方向及面临的挑战.     

农药污染土壤的生物强化修复技术研究进展

生物强化作为一种新型、高效的生物修复技术在污染环境治理中具有独特优势。针对目前土壤农药污染现状,本文介绍了土壤微生物修复方法中的生物强化技术的概念及内涵,探讨了在污染土壤环境中影响生物强化修复效率的生物及非生物因素,重点阐述了生物强化技术在4大类农药(有机氯类、有机磷类、拟除虫菊酯类杀虫剂和三嗪类除草剂)污染土壤修复中的研究进展及应用实例,并提出生物强化技术面临的问题和未来研究方向。     

根际微生物对植物修复重金属污染土壤作用的研究进展

综述了根际微生物对重金属生物有效性的影响,促进植物生长的根际细菌和丛枝菌根真菌在植物修复中的作用,最后介绍了利用生物强化优化植物修复的方法和原则。