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This study aimed to analyze the effect of temperature on performance and microbial community structure of an anaerobic packed bed reactor (APBR). The temperature was increased step-wise from room temperature (22 degrees C ± 1 degrees C) to psychrophilic (15 degrees C ± 1 degrees C), mesophilic (37 degrees C ± 1 degrees C) and thermophilic (55 degrees C ± 1 degrees C). The results showed that, in the temperature changing process, the higher the temperature of APBR was, the higher COD removal rate and daily gas production were. After temperature changed to psychrophilic, mesophilic and thermophilic, COD removal rate and daily gas production were 25%, 45%, 60% and 2.3 L x d(-1), 4.0 L x d(-1), 8.5 L x d(-1) respectively. However, there was no significant change in biogas composition (-60%). A sudden temperature change caused a simultaneous increase in the concentration of volatile fatty acids (VFA), which had been fluctuating. Using 16S rRNA gene clone library screening, Euryarchaeota was commonly found, including important methanogens: MBT (Methanobacteriales), Mst (Methanosaetaceae) , Msc (Methanosarcinaceae) and MMB (Methanomicrobiales), as well as thermophilic bacteria and few spring Archaea. However, the diversity of methanogenic groups was reduced, especially at mesophilic. The results of quantitative PCR showed that the 16S rRNA gene concentrations of Mst, MMB and Msc were reduced by temperature changes. Although the relative proportion of every kind of methanogen was significantly affected, Mst was the dominant methanogen.

Methylmercury (CH3Hg+, or MeHg) is the most poisonous form of mercury (Hg) because it can enter into human bodies through the consumption of Hg-contaminated fish and shellfish. A first step toward bioaccumulation of MeHg in aquatic foods is the methylation of inorganic mercury, a process that is predominantly mediated by anaerobic bacteria, such as sulfate reducing bacteria and iron reducing bacteria. Many researches have confirmed that microbial methylation of mercury is an intracellular reaction. Therefore, MeHg production rates are not only related to the presence and productivity of methylating bacteria and also the biouptake of Hg to these anaerobic bacteria. To understand the pathways of Hg biouptake is indispensable to elucidate the mechanisms of microbial methylation. In this review, we systematically evaluated the current state of knowledge regarding the four pathways of mercury biouptake, Mer-based transport system, passive diffusion, facilitated diffusion and active transport. In the future, facilitated diffusion and active transport of inorganic mercury to the cytoplasm of microbial cells should be emphasized.

The capability of degrading rice straw of lignocellulolytic composite microbial system MC1 was investigated under different methods of preservation and temperatures treatments of 80 degrees C to 95 degrees C, and stability of composite microbial system MC1 was studied through the method of Denaturing Gradient Gel Electrophoresis (DGGE). The results indicate that the rice straw of 2% dry weight of medium can be degraded completely at 50 degrees C within 10 days under static culture. After 9 days inoculating MC1, the dry weight of rice straw, cellulose, hemicellulose and lignin content was degraded by 81% , 99%, 74% and 51%, respectively. Capability of cellulose degrading and stability of composite microbial system MC1 is sustained under 4 years of continuing subculture, 4 years of dry preservation at room temperature, 4 years of preservation at - 20 degrees C, 1 year of liquid preservation at room temperature and at 4 degrees C, and treatment of 90 degrees C for 30 min, respectively. Plate culture results show that composite microbial system MC1 are consisted of bacteria. The main DNA bands are not changed by the method of 16S rDNA PCR-DGGE after culture of six months so that microbial composition of MC1 is very stable.

Four groups of microbial mix culture with considerable capability of cellulose degradation were selected from four compost heaps, by combining the four groups, a composite microbial system MC1 with highly efficient cellulose degradation was obtained. It was found that 0.48 g of filter paper, 0.49 g of absorbent cotton, 0.19 g of wheat straw, or 0.08 g of wood residue can be degraded by 100 mL of MC1 at 50 degrees C with in 72 hours under static culture. The CM1 saccharification activity was much higher at 24th hours when degrading filter paper that was 122.3 U.mL-1. This capability of degradation maintained more than 20 days when the substrates were continually added. MC1 could be inoculated in a wide pH rang, from 4 to 10; however, the final pH would be changed to neutrality after incubation. The pH would be stability with filter paper between 6.0 and 6.5, and between 8.0 and 8.5 without the filter paper.