Monitoring of microbial community structure and succession in the biohydrogen production reactor by denaturing gradient gel electrophoresis (DGGE)

To study the structure of microbial communities in the biological hydrogen production reactor and determine the ecological function of hydrogen producing bacteria, anaerobic sludge was obtained from the continuous stirred tank reactor (CSTR) in different periods of time, and the diversity and dynamics of microbial communities were investigated by denaturing gradient gel electrophoresis (DGGE). The results of DGGE demonstrated that an obvious shift of microbial population happened from the beginning of star-up to the 28th day, and the ethanol type fermentation was established. After 28 days the structure of microbial community became stable, and the climax community was formed. Comparative analysis of 16S rDNA sequences from reamplifying and sequencing the prominent bands indicated that the dominant population belonged to low G+C Gram-positive bacteria (Clostridium sp. andEthanologenbacterium sp.), β-proteobacteria (Acidovorax sp.), γ-proteobacteria (Kluyvera sp.), Bacteroides (uncultured bacterium SJA-168), and Spirochaetes (uncultured eubacterium E1-K13), respectively. The hydrogen production rate increased obviously with the increase ofEthanologenbacterium sp.,Clostridium sp. and uncultured Spirochaetes after 21 days, meanwhile the succession of ethanol type fermentation was formed. Throughout the succession the microbial diversity increased however it decreased after 21 days. Some types ofClostridium sp.Acidovorax sp.,Kluyvera sp., and Bacteroides were dominant populations during all periods of time. These special populations were essential for the construction of climax community. Hydrogen production efficiency was dependent on both hydrogen producing bacteria and other populations. It implied that the cometabolism of microbial community played a great role of biohydrogen production in the reactors.     

Monitoring of microbial community structure and succession in the biohydrogen production reactor by denaturing gradient gel electrophoresis (DGGE)

Biohydrogen production has been concerned ex-tremely as a new technology of energy resource pro-duction by many scientists[1—4]. Enhancement of hy-drogen production efficiency and cutting down the operating cost are very important problems, which are the limiting factors for the industrialization of hydro-gen production process. The fermentation hydrogen production technology offers a new method to resolve these difficulties[5—8]. Compared with photosynthetic hydrogen production possesses, f…     

Phylogenetic and functional diversity of propionate-oxidizing bacteria in an anaerobic digester sludge

The phylogenetic and functional diversity of syntrophic propionate-oxidizing bacteria (POB) present in an anaerobic digester was investigated by microautoradiography combined with fluorescent in situ hybridization (MAR–FISH) that can directly link 16S rRNA phylogeny with in situ metabolic function. The syntrophic POB community in the anaerobic digester sludge consisted of at least four phylogenetic groups: Syntrophobacter, uncultured short rod Smithella (Smithella sp. SR), uncultured long rod Smithella (Smithella sp. LR), and an unidentified group. The activities of these POB groups were dependent on the propionate concentrations. The uncultured Smithella sp. SR accounted for 52–62% of the total active POB under all the propionate concentrations tested (0.5–15 mM). In contrast, uncultured Smithella sp. LR was active only at lower propionate concentrations and became a dominant active POB at 0.5 mM of propionate. Syntrophobacter accounted for 16–31% of the total active POB above 2.5 mM propionate, whereas the active Syntrophobacter population became low (ca. 6%) at 0.5 mM of propionate. The anaerobic digester was operated in a fill and draw mode, resulting in periodical changes in propionate concentration ranging from 0 to 10 mM. These phylogenetically and functionally diverse, to some extent functionally redundant, active POB communities were dynamically responding to the periodical changes in propionate concentration.     

Competition and coexistence of sulfate-reducing bacteria,acetogens and methanogens in a lab-scale anaerobic bioreactor as affected by changing substrate to sulfate ratio

The microbial population structure and function of natural anaerobic communities maintained in lab-scale continuously stirred tank reactors at different lactate to sulfate ratios and in the absence of sulfate were analyzed using an integrated approach of molecular techniques and chemical analysis. The population structure, determined by denaturing gradient gel electrophoresis and by the use of oligonucleotide probes, was linked to the functional changes in the reactors. At the influent lactate to sulfate molar ratio of 0.35 mol mol⁻¹, i.e., electron donor limitation, lactate oxidation was mainly carried out by incompletely oxidizing sulfate-reducing bacteria, which formed 80–85% of the total bacterial population. Desulfomicrobium- and Desulfovibrio-like species were the most abundant sulfate-reducing bacteria. Acetogens and methanogenic Archaea were mostly outcompeted, although less than 2% of an acetogenic population could still be observed at this limiting concentration of lactate. In the near absence of sulfate (i.e., at very high lactate/sulfate ratio), acetogens and methanogenic Archaea were the dominant microbial communities. Acetogenic bacteria represented by Dendrosporobacter quercicolus-like species formed more than 70% of the population, while methanogenic bacteria related to uncultured Archaea comprising about 10–15% of the microbial community. At an influent lactate to sulfate molar ratio of 2 mol mol⁻¹, i.e., under sulfate-limiting conditions, a different metabolic route was followed by the mixed anaerobic community. Apparently, lactate was fermented to acetate and propionate, while the majority of sulfidogenesis and methanogenesis were dependent on these fermentation products. This was consistent with the presence of significant levels (40–45% of total bacteria) of D. quercicolus-like heteroacetogens and a corresponding increase of propionate-oxidizing Desulfobulbus-like sulfate-reducing bacteria (20% of the total bacteria). Methanogenic Archaea accounted for 10% of the total microbial community.     

Electrokinetic remediation and microbial community shift of β-cyclodextrin-dissolved petroleum hydrocarbon-contaminated soil

Electrokinetic (EK) migration of β-cyclodextrin (β-CD), which is inclusive of total petroleum hydrocarbon (TPH), is an economically beneficial and environmentally friendly remediation process for oil-contaminated soils. Remediation studies of oil-contaminated soils generally prepared samples using particular TPHs. This study investigates the removal of TPHs from, and electromigration of microbial cells in field samples via EK remediation. Both TPH content and soil respiration declined after the EK remediation process. The strains in the original soil sample included Bacillus sp., Sporosarcina sp., Beta proteobacterium, Streptomyces sp., Pontibacter sp., Azorhizobium sp., Taxeobacter sp., and Williamsia sp. Electromigration of microbial cells reduced the biodiversity of the microbial community in soil following EK remediation. At 200 V m⁻¹ for 10 days, 36% TPH was removed, with a small population of microbial cells flushed out, demonstrating that EK remediation is effective for the present oil-contaminated soils collected in field.     

水稻秸秆还田时间对土壤真菌群落结构的影响

为揭示水稻秸秆还田对土壤真菌群落结构的长期影响,采用荧光定量PCR和PCR-DGGE技术分析了秸秆还田90,180,270 d和360 d的土壤真菌基因丰度和群落结构组成演变趋势,并利用冗余分析(RDA)研究土壤真菌群落结构变化与环境因子的关系。结果表明:随着秸秆还田时间的增加,土壤真菌群体数量和多样性指数(H、R和E)显著增加,在360 d时达到最高。对DGGE图谱的特征条带进行胶回收、测序,系统进化分析表明,土壤真菌主要种群包括:接合菌(Zygomycete sp.)、盐腐霉菌(Pythium salinum)、肉盘菌(Uncultured Sarcosomataceae)、牛粪盘菌(Ascobolus stercorarius)、大链壶菌(Lagenidium giganteum)、青霉菌(Penicillium sp.)、曲霉属真菌(Aspergillus sp.)和疏绵状丝孢菌(Thermomyces lanuginosus)、灰绿曲霉菌(Aspergillus glaucus)、禾谷多粘菌(Polymyxa graminis)和枝顶孢霉菌(Acremonium sp.),其中青霉菌(Penicillium sp.)、曲霉属真菌(Aspergillus sp.)和枝顶孢霉菌(Acremonium sp.)具有纤维素降解能力,而枝顶孢霉菌(Acremonium sp.)在90 d时成为新的优势菌群。RDA分析表明,90 d和180 d秸秆还田与对照土壤的真菌群落结构较为类似,270 d和360 d的秸秆还田与对照土壤的真菌群落结构发生了明显变化。土壤有机碳、pH和速效磷是引起土壤真菌群落结构及多样性变异的主要因素。     

Analysis of airborne pollen fall in Sakarya, Turkey

In this study, pollen grains were identified using Durham sampler in the atmosphere of Sakarya in 2000 and 2001. During these two years, a total of 10 805 pollen grains were recorded. A total of 5 386 pollen grains per cm² were recorded in 2000 and a total of 5 419 pollen grains per cm² in 2001. Pollen fall in the years 2000–2001 comprised grains belonging to 40 taxa and some unidentified pollen grains. Of these taxa, 22 belonged to arboreal and 18 taxa to non arboreal plants. Total pollen grains consisted of 69.45% grains from arboreal plants, 28.11% grains from non-arboreal plants and 2.44% unidentified pollen grains. In the region investigated, Gramineae, Pinus sp., Quercus sp., Cupressaceae/Taxaceae, Salix sp., Platanus sp., Populus sp., Carpinus sp., Fagus sp., Chenopodiaceae/Amaranthaceae, Xanthium sp., Moraceae, Corylus sp., Fraxinus sp., and Urticaceae released the greatest amount of pollen. The season of maximum pollen fall was from March to May, with a prevalence of arboreal pollen in the first months, and of pollen from non-arboreal plants in the last months of the year.     

Monthly change of community structure of zoobenthos in Xiangxi Bay after impoundment of the Three Gorges Teservoir, China

Xiangxi Bay, a typical bay of the Three Gorges Reservoir (TGR) in China, was formed in June 2003 after the impoundment of the TGR. We investigated the community structure of zoobenthos in Xiangxi Bay from August 2003 to August 2004. Benthic abundance and biomass were calculated per unit area of sediment. A total of 26 taxa were identified. They included two families of Lamellibranchia (7.7% of the total taxa number), two families of Oligochaeta (50%), Chironomidae (38.5%), and one other animal (3.8%). The average density and biomass were 276 ind./m² and 0.301 g/m², respectively. Oligochaetes and chironomids constituted the major groups, and Limnodrilus hoffmeisteri, Procladius sp., Branchiura sowerbyi, Tubificidae sp1. and Polypedilum scalaenum group sp. were the common taxa in this reservoir system. Among them, L. hoffmeisteri and Procladius sp. were the dominant species, and contributed 37.0% and 28.3% of the total density, respectively. The standing crop of zoobenthos in Xiangxi Bay was relative low, compared with other similar reservoirs. Our studies demonstrate that the standing crop increased gradually with time. The total density and biomass in August 2004 were 8.8 and 14.3 times those of the initial impoundment, separately. Oligochaetes did not become the sole dominant group, indicating that the sediment loading in Xiangxi Bay may be not serious. __________ Translated from Acta Hydrobiologica Sinica, 2006, 30(1): 64–69 [译自: 水生生物学报]     

Variation over Time in Parasite Prevalence Among Free-ranging Chimpanzees at Gombe National Park,Tanzania

From January to September, 2005, we collected fecal samples from 60 chimpanzees at Gombe National Park, Tanzania and examined them for parasites. We compared current parasite prevalence data with previous studies to obtain a pattern of parasitism over time. There were considerable similarities in the parasite species composition and prevalence, although we noted some variations. Generally, parasite prevalence decreased over time, with the present prevalence being lower than in previous surveys. We identified 8 types of parasites, all of which had previously been documented in the chimpanzees of Gombe. Three nematodes — Oesophagostomum sp., Strongyloides fulleborni, and Abbreviata caucassica— occurred at higher prevalence (41.2–45.5%) but relatively lower than previous findings of 50–91%. We also diagnosed unidentified strongyles at a moderate prevalence (33%), lower than a previous record of 41%. Probstmayria gombensis occurred at relatively low prevalence (16.4%) vs. past observations (23–59%), while the prevalence of Trichuris sp. (7.3%) was closely similar to previous records of 5–9%. We also observed unidentified ciliate at 9% within the same range as in previous studies (5–28%). The prevalence of Troglodytella abrassarti was 78%, closely similar to previous findings of 75%. There was no significant variation in parasite prevalence between chimpanzees of the Kasekela community and those of the Mitumba community, although the former tended to have higher prevalence of helminths than the latter. The causes of the similarities and variations in parasite prevalence over time are discussed. The study provides baseline data for monitoring of chimpanzee health at Gombe.     

高寒森林溪流微生物群落结构的季节性变化

高寒森林溪流不仅是区域河流的源头,而且是联系陆地与水域的生态纽带。微生物活动可能成为控制溪流生态系统过程的关键因子,但其结构与动态过程缺乏必要关注。因此,结合同步温度动态监测,采用实时荧光定量PCR和DGGE技术,在2014年到2015年冻融季节和生长季节关键时期对比研究了川西高寒森林溪流和森林林下土壤中微生物群落的动态特征。研究结果发现,高寒森林溪流具有较低的真菌和细菌群落丰度;与森林土壤相同,溪流在冻融季节表现出相对生长季节更高的真菌/细菌比,而且从冻融季节到生长季节,溪流微生物丰度动态也表现出明显的季节性变化特征。与森林土壤不同的是,溪流中细菌和真菌的丰度及其Shannon-Wiener多样性指数的最高值均出现在生长季节而不是冬季冻融季节,并且溪流中细菌丰度在季节性变化的不同时期具有显著差异(P0.05)。此外,森林土壤细菌类群以芽孢杆菌属(Bacillus sp.)比例相对较高,真菌类群则以格孢菌属(Pleosporales sp.)、曲霉属(Aspergillus sp.)和其他一些子囊菌门(Ascomycota)的类群为优势;而溪流细菌类群以红球菌属(Rhodococcus sp.)为主,真菌类群则以曲霉属和空团菌属(Cenococcum sp.)为主。同时,季节性变化中温度、p H、水溶性有机碳和溶解氧等环境因子可显著影响溪流微生物群落结构及其组成,这些环境因子在高寒森林溪流微生物群落的季节性变化过程中具有重要的作用。     

Microbial community dynamics in anaerobic bioreactors and algal tanks treating piggery wastewater

Integrated biosystem is becoming a major aspect of wastewater management practice. Microbial communities in piggery wastewater sampled from anaerobic (thermophilic and mesophilic) and aerobic digesters (algal tanks) during waste remediation were analyzed by culture-independent techniques based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The use of Muyzer's 314F-GC, 518R bacterial primers, and archaeal A934F, 1309R primers followed by partial 16s rDNA sequence analysis of the main bands from DGGE revealed the presence of unknown and as yet uncultured microorganisms but also showed functional and ecologically significant denitrifying, acetogenic bacteria along with autotrophic, hydrogenotrophic, and acetoclastic methanogen archaea. Thermophilic digesters were dominated by γ-Proteobacteria, Methanothermobacter sp., while mesophilic digesters showed dominance by Firmicutes, uncultured bacteria, Methanosarcina, and Methanoculleus genera. Under aerobic conditions within algal tanks, pH rose from 7.17 to 9.32, with a significant decrease in total ammonia nitrogen, chemical oxygen demand, and soluble phosphorus levels. PCR-DGGE proved a useful tool for investigating the dynamics of microbial community in the bio-processing of piggery wastewater. Knowledge of the microbial communities involved in digestion of piggery wastewater will allow optimization of integrated biosystem by removing the main pollutants like inorganic ammonium-nitrogen, phosphorus, and pathogens from intensive farming system.     

First Quantitative Study of Rove Beetles in Oklahoma Winter Wheat Fields

Adult rove beetles (Staphylinidae) were sampled every 7–14 days from one winter wheat field located in each of the four major wheat growing regions of Oklahoma during the 1999–2000 and 2000–2001 growing seasons. The number of cereal aphids per tiller, wheat plant growth stage, and wheat tiller density also were estimated. A total of 12 genera representing 13 species of beetles were collected from the field. The density of rove beetles was generally low, ranging from 0.003 beetles per m² in fall to 0.106 beetles per m² in spring. Rove beetle communities differed among seasons. After accounting for the effect of season, there was no statistically significant association between rove beetle community structure and field location, aphid density, wheat plant growth stage, or wheat plant density. Most rove beetle species showed no association with a particular season, however, Aleochara notula Erichson, Lathrobium sp., and Oxypoda sp. were present predominantly in fall, while Bisnius inquitus Erichson was associated with winter. Oxypoda sp. was the most abundant rove beetle in winter wheat fields in spring and was relatively abundant in winter, but was not collected from wheat fields in fall. Tachyporus jocosus Say was present in wheat fields during all seasons. T. jocosus was the most abundant rove beetle species in the winter wheat fields in fall and winter and was the second most abundant species during spring.     

Spatiotemporal development of the bacterial community in a tubular longitudinal microbial fuel cell

The spatiotemporal development of a bacterial community in an exoelectrogenic biofilm was investigated in sucrose-fed longitudinal tubular microbial fuel cell reactors, consisting of two serially connected modules. The proportional changes in the microbial community composition were assessed by polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) and DNA sequencing in order to relate them to the performance and stability of the bioelectrochemical system. The reproducibility of duplicated reactors, evaluated by cluster analysis and Jaccard’s coefficient, shows 80–90% similarity in species composition. Biofilm development through fed-batch start-up and subsequent stable continuous operation results in a population shift from γ-Proteobacteria- and Bacteroidetes- to Firmicutes-dominated communities, with other diverse species present at much lower relative proportions. DGGE patterns were analysed by range-weighted richness (Rr) and Pareto–Lorenz evenness distribution curves to investigate the evolution of the bacterial community. The first modules shifted from dominance by species closely related to Bacteroides graminisolvens, Raoultella ornithinolytica and Klebsiella sp. BM21 at the start of continuous-mode operation to a community dominated by Paludibacter propionicigenes-, Lactococcus sp.-, Pantoea agglomerans- and Klebsiella oxytoca-related species with stable power generation (6.0 W/m³) at day 97. Operational strategies that consider the dynamics of the population will provide useful parameters for evaluating system performance in the practical application of microbial fuel cells.     

Impact of different developmental stages of <Emphasis Type="Italic">Daphnia</Emphasis> <Emphasis Type="Italic">magna</Emphasis> (Straus) on the plankton community under different trophic conditions

In situ 24-h incubation experiments were performed to analyse the grazing effects of Daphnia magna on a planktonic microbial community. Three field grazing experiments under different nutrient concentrations were carried out on treated effluents of a wastewater treatment plant. The grazing effects of three different D. magna size classes (small (0.6–1.6 mm), medium (1.7–2.5 mm) and large individuals (2.6–3.7 mm)) were compared. The different sizes classes had similar effects on the plankton community. However, our results showed big differences in effects among experiments. Our findings suggest that in spite of D. magna’s non-selective feeding behaviour and the fact that different developmental stages (i.e. its size) had similar effects on the microbial planktonic community, these effects can differ according to the initial structure and composition of the community and the resulting cascading trophic interactions. Moreover, D. magna effects can be direct through grazing (as is the case with ciliates), or indirect through trophic cascade interactions (as is the case with bacteria).     

Bacteria Associated with the Bleached and Cave Coral Oculina patagonica

The relative abundance of bacteria in the mucus and tissues of Oculina patagonica taken from bleached and cave (azooxanthellae) corals was determined by analyses of the 16S rRNA genes from cloned libraries of extracted DNA and from isolated colonies. The results were compared to previously published data on healthy O. patagonica. The bacterial community of bleached, cave, and healthy corals were completely different from each other. A tight cluster (>99.5% identity) of bacteria, showing 100% identity to Acinetobacter species, dominated bleached corals, comprising 25% of the 316 clones sequenced. The dominant bacterial cluster found in cave corals, representing 29% of the 97 clones sequenced, showed 98% identity to an uncultured bacterium from the Great Barrier Reef. Vibrio splendidus was the most dominant species in healthy O. patagonica. The culturable bacteria represented 0.1–1.0% of the total bacteria (SYBR Gold staining) of the corals. The most abundant culturable bacteria in bleached, cave, and healthy corals were clusters that most closely matched Microbulbifer sp., an α-proteobacterium previously isolated from healthy corals and an α-protobacterium (AB026194), respectively. Three generalizations emerge from this study on O. patagonica: (1) More bacteria are associated with coral tissue than mucus; (2) tissue and mucus populations are different; (3) bacterial populations associated with corals change dramatically when corals lack their symbiotic zooxanthellae, either as a result of the bleaching disease or when growing in the absence of light.     

Diversity of the resident microbiota in a thermophilic municipal biogas plant

Biogas plants continuously convert biological wastes mainly into a mixture of methane, CO₂ and H₂O—a conversion that is carried out by a consortium of bacteria and archaea. Especially in the municipal plants dedicated towards waste treatment, the reactor feed may vary considerably, exposing the resident microbiota to a changing variety of substrates. To evaluate how and if such changes influence the microbiology, an established biogas plant (6,600 m³, up to 600 m³ biogas per h) was followed over the course of more than 2 years via polymerase chain reaction–denaturing gradient gel electrophoresis of 16S rRNA genes and subsequent sequencing. Both the bacterial and the archaeal community remained stable over the investigation. Of the bacterial consortium, about half of the sequences were in decreasing order of occurrence: Thermoacetogenium sp., Anaerobaculum mobile, Clostridium ultunense, Petrotoga sp., Lactobacillus hammesii, Butyrivibrio sp., Syntrophococcus sucromutans, Olsenella sp., Tepidanaerobacter sp., Sporanaerobacter acetigenes, Pseudoramibacter alactolyticus, Lactobacillus fuchuensis or Lactobacillus sakei, Lactobacillus parabrevis or Lactobacillus spicheri and Enterococcus faecalis. The other half matched closely to ones from similar habitats (thermophilic anaerobic methanogenic digestion). The archaea consisted of Methanobrevibacter sp., Methanoculleus bourgensis, Methanosphaera stadtmanae, Methanimicrococcus blatticola and uncultured Methanomicrobiales. The role of these species in methane production is discussed.     

The effect of decreasing alkalinity on microbial community dynamics in a sulfate-reducing bioreactor as analyzed by PCR-SSCP

Alkalinity refers to the substance that can react with acid in an aqueous system, which measures its capac-ity to neutralize hydrogen iron (H ). Alkalinity influ-ences greatly the stability and treatment ability of an-aerobic bioreactor. It has been well …     

Responses of soil microbial communities to prescribed burning in two paired vegetation sites in southern China

Prescribed burning is a common site preparation practice for forest plantation in southern China. However, the effects of prescribed burning on soil microbial communities are poorly understood. This study examined changes in microbial community structure, measured by phospholipid fatty acids (PLFAs), after a single prescribed burning in two paired vegetation sites in southern China. The results showed that the total amount of PLFA (totPLFA) was similar under two vegetation types in the wet season but differed among vegetation type in the dry season, and was affected significantly by burning treatment only in the wet season. Bacterial PLFA (bactPLFA) and fungal PLFA (fungPLFA) in burned plots all decreased compared to the unburned plots in both seasons (P = 0.059). Fungi appeared more sensitive to prescribed burning than bacteria. Both G⁺ bacterial PLFA and G⁻ bacterial PLFA were decreased by the burning treatment in both dry and wet seasons. Principal component analysis of PLFAs showed that the burning treatment induced a shift in soil microbial community structure. The variation in soil microbial community structure was correlated significantly to soil organic carbon, total nitrogen, available phosphorus and exchangeable potassium. Our results suggest that prescribed burning results in short-term changes in soil microbial communities but the long-term effects of prescribed burning on soil microbial community remain unknown and merit further investigation.     

The effect of decreasing alkalinity on microbial community dynamics in a sulfate-reducing bioreactor as analyzed by PCR-SSCP

PCR-single-strand conformation polymorphism (SSCP) and Southern blotting techniques were adopted to investigate microbial community dynamics in a sulfate-reducing bioreactor caused by decreasing influent alkalinity. Experimental results indicated that the sulfate-removal rate approached 87% in 25 d under the conditions of influent alkalinity of 4000 mg/L (as CaCO₃) and sulfate-loading rate of 4.8 g/(L·d), which indicated that the bioreactor started up successfully. The analysis of microbial community structure in this stage showed that Lactococcus sp., Anaerofilum sp. and Kluyvera sp. were dominant populations. It was found that when influent alkalinity reduced to 1000 mg/L, sulfate-removal rate decreased rapidly to 35% in 3 d. Then influent alkalinity was increased to 3000 mg/L, the sulfate-removal rate rose to 55%. Under these conditions, the populations of Dysgonomonas sp., Sporobacte sp., Obesumbacterium sp. and Clostridium sp. got to rich, which predominated in the community together with Lactococcus sp., Anaerofilum sp. and Kluyvera sp. However, when the alkalinity was decreased to 1500 mg/L, the sulfate-removal rate rose to and kept stable at 70% and populations of Dysgonomonas sp., Sporobacter sp. and Obesumbacterium sp. died out, while some strains of Desulfovibrio sp. and Clostridium sp. increased in concentration. In order to determine the minimum alkalinity value that the system could tolerate, the influent alkalinity was decreased from 1500 to 400 mg/L secondly. This resulted in the sulfate-removal rate, pH value and effluent alkalinity dropping quickly. The amount of Petrotoga sp., Prevotella sp., Kluyvera sp. and Neisseria sp. reduced obviously. The result data from Southern blotting indicated that the amount of sulfate-reducing bacteria (SRBs) decreased with influent alkalinity dropping. Analysis of the microbial community structure and diversity showed that the SRBs populations were very abundant in the inoculated activated sludge and the alkalinity decrease caused the reduction of the populations noted. Most of resident populations in the bioreactor were fermentative acidogenic bacteria (FABs), among which the phylum Firmicute was in the majority, but SRBs were very few. This community structure demonstrates the cooperation between SRBs and FABs, which sustains the system’s high sulfate-removal and operation stability.     

Immobilization of cells by entrapping in aubasidan

A new technique of immobilization of microbial cells by entrapping in aubasidan, a microbial polysaccharide, was developed. This technique was applied to three cultures:Erwinia aroidea, Pseudomonas sp., andAlcaligenes faecalis, the producers of aspartase and L-aspartate β-decarboxylase. The new method is effective. After immobilization, microbial cells retained 79–91% of their initial enzymatic activity.