Function Of Microbial Populations Research Articles

Different micro-aeration rates facilitate production of different end-products from source-diverted blackwater

The effects of micro-aeration on the performance of anaerobic sequencing batch reactors (ASBR) for blackwater treatment were investigated in this study. Different micro-aeration rates, 0, 5, 10, 50, and 150 mg O2/L-reactor/cycle, and their effect on the hydrolysis, acidogenesis, and methanogenesis of blackwater were evaluated and compared at ambient temperature. Source-diverted blackwater (toilet water) contains high organic contents which can be recovered as biogas. Previous studies have found that anaerobic digestion of blackwater without micro-aeration can only recover upwards of less than 40% of chemical oxygen demand (COD) to methane at room temperature due to the low hydrolysis rate of biomass content in blackwater. This study achieved increases in blackwater hydrolysis (from 34.7% to 48.7%) and methane production (from 39.6% to 50.7%) with controlled micro-aeration (5 mg O2/L-reactor/cycle). The microbial analysis results showed that hydrolytic/fermentative bacteria and acetoclastic methanogens (e.g. Methanosaeta) were in higher abundances in low-dose micro-aeration reactors (5 and 10 mg O2/L-reactor/cycle), which facilitated syntrophic interactions between microorganisms. The relative abundance of oxygen-tolerant methanogen such as Methanosarcina greatly increased (from 1.5% to 11.4%) after oxygen injection. High oxygen dosages (50 and 150 mg O2/L-reactor/cycle) led to reduced methane production and higher accumulation of volatile fatty acids, largely due to the oxygen inhibition on methanogens and degradation of organic matters by aerobic growth and respiration, as indicated by the predicted metagenome functions. By combining reactor performance results and microbial community analyses, this study demonstrated that low-dose micro-aeration improves blackwater biomethane recovery by enhancing hydrolysis efficiency and promoting the development of a functional microbial population, while medium to high-dose micro-aeration reduced the activities of certain anaerobes. It was also observed that medium-dose micro-aeration maximizes VFA accumulation, which may be used in two-stage anaerobic digesters.

Aerobic anoxygenic photosynthesis bacteria (AAPB) associated with aquatic ecosystems

好氧不产氧光合细菌（aerobic anoxygenic photosynthesis bacteria，AAPB）是广泛分布于海洋、湖泊及河流等典型水域生境中的异养原核生物，能够以环境中有机物为营养物质来获取细胞生长及代谢所需的能量，同时借助自身独特的菌绿素完成光合作用产能但不合成氧气，在物质循环与能量流动中扮演着重要角色.近年，越来越多的AAPB种属被陆续报道，基于光合基因，例如光合反应中心M亚基（pufM）的分子系统发育分析显示，大部分AAPB属于α-、β-及γ-变形菌，且丰度及多样性随生境的不同而呈现时空地理格局异质性.本文对AAPB的栖息环境与生长特性、丰度与分布、生态功能以及环境驱动因子等方面的研究进展进行了回顾和综述.目前，针对水库生态系统AAPB的研究鲜见报道，作者建议开展水库生境中AAPB多样性分布、环境驱动因素及生态功能研究，丰富对于水生生态系统中功能微生物种群生态结构与代谢功能的认识.;Aerobic anoxygenic photosynthesis bacteria (AAPB) are heterotrophic prokaryotes widely distributed in typical water habitats such as oceans, lakes, and rivers. They can use organic matter in the environment as nutrients to obtain energy for cell growth and metabolism absorb organic matter from environment to maintain cell growth and metabolism but also rely on its own unique chlorophyll to complete the photosynthesis without oxygen production, playing an important role in water material circulation and energy flow. In recent years, more and more AAPB species have been reported one after another. Based on molecular phylogenetic analysis of photosynthetic genes such as the M subgene (pufM) of the photosynthetic reaction center, most AAPB belong to Alpha-, Beta-, and Gamma-proteobacteria. Moreover, the abundance and diversity of AAPB show heterogeneity in spatial and temporal geographic pattern varying with habitats. This article reviews and summarizes the research progress on AAPB's habitats and growth characteristics, abundance and distribution, ecological functions, and environmental drivers. At present, there are few reports on AAPB in reservoir ecosystems. The author proposes to conduct research on AAPB diversity distribution, environmental driving factors and ecological functions in reservoir habitats to enrich the understanding of the ecological structure and metabolic functions of functional microbial populations in aquatic ecosystems.

Understanding how long-term organic amendments increase soil phosphatase activities: Insight into phoD- and phoC-harboring functional microbial populations

In context of the use of organic materials as alternatives for mineral fertilizer, it is important to understand how organic amendments influence soil extracellular phosphatase activities which accelerate the mineralization of organic phosphorus (P). To address this, the current study investigates the influence of organic amendments on acid (ACP) and alkaline (ALP) phosphatase activities in soils and how organic amendments influence these activities from the perspective of microbially-mediated pathways. Herein, a comprehensive meta-analysis of 599 measurements from 106 published studies around the world was performed as well as a field component sourced from a 30-year-old field experiment on fertilization. Based on meta-analysis, organic amendments increased average extracellular ACP and ALP activities by 22% and 53%, respectively, in comparison to the mineral-only fertilization. Observed increases in activities were consistent with significant increases in soil organic carbon (C), total nitrogen (N) and available P contents, and microbial biomass C and N pools. According to the data from the long-term field experiment, we found phoD-harboring species encoding ALP were more closely correlated with phoC-harboring species encoding ACP in organically amended soils, and more network hubs were also observed by organic amendment. Soil C:P and N:P ratios, and microbial biomass C were the main predictors of the abundance, diversity, and composition of the phoC- and phoD-harboring populations. Further analysis revealed that the soil C:P ratio was identified as the dominant predictor of potential ACP and ALP activities. Our work highlights the importance in understanding how soil C:N:P stoichiometry mediates phosphatase-harboring populations in order to determine the downstream consequences of using organic amendments for increasing phosphatase activities.

Host transcriptome and microbiome interaction modulates physiology of full-sibs broilers with divergent feed conversion ratio

Efficient livestock production relies on effective conversion of feed into body weight gain (BWG). High levels of feed conversion are especially important in production of broiler chickens, birds reared for meat, where economic margins are tight. Traits associated with improved broiler growth and feed efficiency have been subjected to intense genetic selection, but measures such as feed conversion ratio (FCR) remain variable, even between full siblings (sibs). Non-genetic factors such as the composition and function of microbial populations within different enteric compartments have been recognized to influence FCR, although the extent of interplay between hosts and their microbiomes is unclear. To examine host–microbiome interactions we investigated variation in the composition and functions of host intestinal-hepatic transcriptomes and the intestinal microbiota of full-sib broilers with divergent FCR. Progeny from 300 broiler families were assessed for divergent FCR set against shared genetic backgrounds and exposure to the same environmental factors. The seven most divergent full-sib pairs were chosen for analysis, exhibiting marked variation in transcription of genes as well as gut microbial diversity. Examination of enteric microbiota in low FCR sibs revealed variation in microbial community structure and function with no difference in feed intake compared to high FCR sibs. Gene transcription in low and high FCR sibs was significantly associated with the abundance of specific microbial taxa. Highly intertwined interactions between host transcriptomes and enteric microbiota are likely to modulate complex traits like FCR and may be amenable to selective modification with relevance to improving intestinal homeostasis and health.

Taxonomic and functional characterization of a microbial community from a volcanic englacial ecosystem in Deception Island, Antarctica

Glaciers are populated by a large number of microorganisms including bacteria, archaea and microeukaryotes. Several factors such as solar radiation, nutrient availability and water content greatly determine the diversity and abundance of these microbial populations, the type of metabolism and the biogeochemical cycles. Three ecosystems can be differentiated in glaciers: supraglacial, subglacial and englacial ecosystems. Firstly, the supraglacial ecosystem, sunlit and oxygenated, is predominantly populated by photoautotrophic microorganisms. Secondly, the subglacial ecosystem contains a majority of chemoautotrophs that are fed on the mineral salts of the rocks and basal soil. Lastly, the englacial ecosystem is the least studied and the one that contains the smallest number of microorganisms. However, these unknown englacial microorganisms establish a food web and appear to have an active metabolism. In order to study their metabolic potentials, samples of englacial ice were taken from an Antarctic glacier. Microorganisms were analyzed by a polyphasic approach that combines a set of -omic techniques: 16S rRNA sequencing, culturomics and metaproteomics. This combination provides key information about diversity and functions of microbial populations, especially in rare habitats. Several whole essential proteins and enzymes related to metabolism and energy production, recombination and translation were found that demonstrate the existence of cellular activity at subzero temperatures. In this way it is shown that the englacial microorganisms are not quiescent, but that they maintain an active metabolism and play an important role in the glacial microbial community.

The dynamics of functional microbes population in two depths under raru (Cotylelobium spp) stand

Raru (Cotylelobium spp) is one of the endemic plants in North Sumatra from the Dipterocarpaceae family. Plant growth is strongly influenced by the condition of the soil environment. Soil provides nutrients to increase plant growth. Soil also a habitat for various microbes that affect plant growth. This study aimed to calculate functional microbial populations under raru stands such as arbuscular mycorrhizal fungi, phosphate solubilizing microbes, and cellulose decomposer microbes. The measurement of the population use plate count methods. Soil samples were taken in composite with 0-5 cm and 5-20 cm in the raru pulut, raru dahanon and raru songal rhizosphere area in Bona Lumban Village, Tukka District, Central Tapanuli Regency North Sumatra. The result showed that a functional microbial population was calculated higher at a depth of 0-5 cm compared to a depth of 5-20 cm. The microbial population of phosphate solubilizing microbes ranged from 10.12x 103 to 92.44x103 CFU mL−1 with the largest population found in the raru songal rhizosphere. Cellulose decomposer microbial populations ranged from 6.21x103 to 21.55x103 CFU mL-1 with the highest population found in the raru pulut rhizosphere. The highest arbuscular mycorrhizal fungi density in raru dahanon rhizosphere.

Uji Formulasi Pupuk Hayati Padat Berbasis Azolla Terhadap Populasi dan Fungsional Mikroba Tanah Menguntungkan

Inorganic fertilizer is a very important agricultural input to increase agricultural production. Uncalculated and continuous application of inorganic fertilizers will lead to the reduction of soil fertility and degradation of environmental quality. Therefore, a strategy is needed to support the environmental sustainability in agriculture. One of the efforts is through the production of biofertilizer and organic fertilizer from local resources. Organic fertilizer for rice plants can be made by utilizing the local water fern, Azolla pinnata. A. pinnata can be applied on rice fields as green manure by directly placing it into the soil or spread on the surface of rice fields. Organic fertilizer that made from Azolla will be more advantageous because it can be applied with biofertilizer. This study aimed to determine the formulation of Azolla based solid biofertilizer that can support the growth of functional microbial population based on the Agriculture Ministry (Permentan) standard number 70/2011. The design of the study method used was Completely Randomized Design with six replications. The treatments used were inoculant starter with 3% molasses, 3% molasses + 10% rice wash water, 3% molasses + 1% yeast extract, and 3% molasses + 10% rice wash water + 1% yeast extract. The results of this study showed that Azolla-based solids fertilizer with starter formula 3% inoculant molasses + 10% rice water + 1% yeast extract have the population of Azotobacter, Azospirillum, endophytic bacteria and phosphate solubilizing microbe were greater than 108 cfu/g dry weight. Functional microbial of solids fertilizers in all formulas used do not show the difference on inhabiting in the N-free media or Pikovskaya selective media. Keywords: Azolla pinnata, formulation, biofertilizer, organic fertilize

Nitrogen fertilizer is a key factor affecting the soil chemical and microbial communities in a Mollisol.

Microbial communities drive geochemical cycles in soils. Relatively few studies have assessed the long-term impacts of different types of soil amendments under field conditions in long-term experiments. The response of soil microbial organisms in a Mollisol cultivated with maize for 35 years was examined. Treatments involved the use of N, P, and K fertilizers and two doses of straw residue in isolation or combined. Real-time PCR and Illumina MiSeq sequencing methods were used to characterize the microbial community. The results showed that addition of nitrogen fertilizers decreased soil pH, but this was mitigated when a high dose of straw was also incorporated. Long-term application of inorganic fertilizers was able to alter the abundance of functional soil microbial population. Application of inorganic N fertilizer resulted in distinctive changes on N-cycle microorganisms. Phosphate-solubilizing functional genes abundance was lower in plots with no phosphate fertilizer. Sequencing analysis showed that the presence or absence of N in the fertilizer mix is a key factor affecting bacterial community diversity of agricultural soil, and pH, total organic C, and total N show a high correlation with bacterial community composition. Nitrogen addition increased the N concentration in the soil, which could cause changes in the soil pH and change the soil bacterial community. Our findings proved that interaction of N fertilizer with other fertilizers can affect microbial communities.

Optimization of Mixed Cultivation of the Moderate Thermophilic Bioleaching Microorganisms for High Cell Density Using Statistical Methodology

The low functional microbial population density in the industrial bioleaching process has been a limiting factor for the high leaching efficiency, making the microbial cultivation and continuous inoculation an alternative for sustaining the microbial activity. In the present experiment, the defined mixed cultivation of Leptospirillum ferriphilum YSK, Sulfobacillus acidophilus TPY, Acidithiobacillus caldus S2, and Ferroplasma thermophilum L1 was evaluated and optimized by Statistical Methodology. Going through the Plackett–Burman experimental design, pH value, temperature, and c(MgSO4·7H2O) were considered as the most significant factors in the defined range. Then, the relationships were analyzed using the steepest ascent design, the central composite design, and finally the response surface methodology. It was suggested that the optimum parameters were pH 1.38, MgSO4·7H2O 0.552 g/L, temperature 44 °C, FeSO4·7H2O 40 g/L, sulfur 8 g/L, yeast 0.02% w/v, (NH4)2SO4 3g/L, K2HPO4 0.5g/L, KCl 0.1g/L, Ca(NO3)2 0.01 g/L, in which allowed total cell density of the microbial community to reach 7.63 × 108 cells/mL in the cultivation period. The lab experiments were routinely undertaken with the expectation that the L. ferriphilum YSK, S. acidophilus TPY, A. caldus S2, F. thermophilum L1 could rapid grown from initial cell density of 0.25 × 107 cells/mL to 2.82 × 108 cells/mL, 1.68 × 108 cells/mL, 2.76 × 108 cells/mL, 2.51 × 107 cells/mL, respectively in 58 h. It demonstrates a possibility to co-culture these microbes in a single reactor, providing an efficient way to regenerate of inoculation for biomining process.

Effect of Substrate Conversion on Performance of Microbial Fuel Cells and Anodic Microbial Communities.

Performance of microbial fuel cells (MFCs) was monitored during the influent nutrient change from lactate to glucose/acetate/propionate and then to lactate. Meanwhile, anodic microbial communities were characterized by culture-independent molecular biotechnologies. Results showed MFC performance recovered rapidly when the lactate was replaced by one of its metabolic intermediates acetate, while it needed a longer time to recover if lactate substrate was converted to glucose/propionate or acetate to lactate. Secondary lactate feed enhanced the enrichment of bacterial populations dominating in first lactate feed. Electricity-producing bacteria, Geobacter spp., and beneficial helpers, Anaeromusa spp. and Pseudomonas spp., revived from a low abundance as lactate secondary supply, but microbial communities were hard to achieve former profiles in structure and composition. Hence, microbial community profiles tended to recover when outside environmental condition were restored. Different substrates selected unique functional microbial populations.

Effects of Bacitracin and Bacitracin Zinc on In Vitro Fermentation, Methane Production and Microbial Populations of the Rumen

This study was conducted to investigate the effects of bacitracin (B) and bacitracin zinc (BZ) on in vitro fermentation, methane and ammonia production, and select microbial populations of the rumen. Both B and BZ were added at 3 doses, namely 10 (low), 30 (medium), and 90 (high) mg/l of in vitro fermentation medium. Results showed that B and BZ had similar effects on rumen fermentation characteristics and microbial populations. Low dosage of B or BZ addition reduced (P 0.05) on total VFA concentration and feed digestibility. The population of total bacteria was unaffected (P>0.05) by low B and BZ doses, but was significantly (P 0.05) on the populations of protozoa and fungi. Results indicated that optimum B or BZ addition could reduce methane and ammonia production, with no adverse effects on total VFA concentration and feed digestibility. Further, these effects are probably associated with the variation of rumen functional microbial populations.

EVALUASI POPULASI MIKROBA FUNGSIONAL PADA PUPUK ORGANIK KOMPOS (POK) MURNI DAN PUPUK ORGANIK GRANUL (POG) YANG DIPERKAYA DENGAN PUPUK HAYATI

Organic fertilizer is a fertilizer that is expected to improve the physical, chemical, and biological properties of the agricultural land resources, which is undergoing fertilityand productivity degradation. Compost is one of the organic fertilizers produced from the biological decomposition process by a consortium of microorganisms, includingfunctional microorganisms. To make it easier for farmers and efficiency in the use of organic fertilizer, organic fertilizer will be further processed into granular form and is called Granules Organic Fertilizer (POG). In the manufacturing process, namely at the time of drying using a rotary dryer, was suspected of using high temperatures to kill microbes (including functional microbial) that naturally exist in the organic compost fertilizer (POK), which is the raw material for POG. To increase the presence of functional microbial populations, the POG which has produced before, then added with bio fertilizer that is rich in microbial functional. This research was conducted to determine and evaluate the total microbial population and functional microbial in pure POK, compared with the total microbial population and functional microbial in the POG are enriched with bio-fertilizer. The results showed: There is an indication to the higher number of total microbial population in the POK, who showed by total fungi population, compared with the POG. The number of functional microbial population, as shown by bacterial phosphate solvent and non-symbiotic bacteria that are fastening N in POK, very high and already meets the criteria to be called as a biological fertilizer. The amount is not significantly different compared to the POG that is already enriched with bio fertilizer that is rich in microbial functional. There is an indication of the influence of high heating using a rotary dryer, in the POG manufacturing process against the decreasing of the amount of microbialpopulation that are resulting in the POG, including functional microbial

Detection of N-Acyl-homoserine Lactones Signal Molecules of Quorum Sensing Secreted by Denitrification Flora in Microaerobic Nitrogen Removal Processes by Ultra-performance Liquid Chromatography Tandem Mass Spectrometry

Abstract Gram-negative (G−) bacteria, such as denitrifying bacteria and anaerobic ammonia oxidation bacteria, are highly social organisms capable of sophisticated cooperative behavior mediated via quorum sensing. As the signal molecules of chemical communication, N-acyl-homoserine lactones (AHLs) can mediate the quorum sensing of the functional microbial population and regulate the population density. To understand the growth of functional microbial population and the mechanism for biological nitrogen removal in upflow microaerobic sludge reactors (UMSRs) treating organic wastewater with low ratio of chemical oxygen demand to total nitrogen, a method was established to simultaneously detect AHLs in the microaerobic processes. Water-sludge mixtures sampled from the UMSRs were pretreated in sequence by liquid-liquid extraction using ethyl acetate, rotary evaporation, constant volume with methanol, and separation by C18 column. Gradient elution was carried out using 5 mM ammonium acetate (containing 0.1% formic acid) and methanol as mobile phases. On the base of multiple reaction monitoring analysis, a triple quadrupole mass spectrometer with an electrospray ionization was applied to detect the target compounds. 9 kinds of AHLs were used to evaluate the established method and the results showed that the detection limits were 0.01−0.5 μg L−1 and all of the AHLs presented excellent linearity with the concentration ranged from 0.5 μg L−1 to 100 μg L−1. The recovery and relative standard deviation ranged from 62.5% to 118.1% and 2.9% to 12.1%, respectively. The analysis was completed within 6.5 min. The rapid, accurate and precise method for detecting AHLs provides a new insight into the growth and metabolic activity of functional microbial population in the activated sludge processes to understand the mechanism of biological nitrogen removal, suggesting a good application in regulation and operation of wastewater biological treatment processes.

Performance, 5-aminolevulinic acid (ALA) yield and microbial population dynamics in a photobioreactor system treating soybean wastewater: Effect of hydraulic retention time (HRT) and organic loading rate (OLR)

Effects of hydraulic retention time (HRT) and influent organic loading rate (OLR) were investigated in a photobioreactor containing PNSB (Rhodobacter sphaeroides)-chemoheterotrophic bacteria to treat soybean wastewater. Pollutants removal, biomass production and ALA yield in different phases were investigated in together with functional microbial population dynamics. The results showed that proper HRT and OLR increased the photobioreactor performance including pollutants removal, biomass and ALA productions. 89.5% COD, 90.6% TN and 91.2% TP removals were achieved as well as the highest biomass production of 2655mg/L and ALA yield of 7.40mg/g-biomass under the optimal HRT of 60h and OLR of 2.48g/L/d. In addition, HRT and OLR have important impacts on PNSB and total bacteria dynamics.

Microbial Community Structure and Arsenic Biogeochemistry in an Acid Vapor-Formed Spring in Tengchong Geothermal Area, China.

Arsenic biogeochemistry has been studied extensively in acid sulfate-chloride hot springs, but not in acid sulfate hot springs with low chloride. In this study, Zhenzhuquan in Tengchong geothermal area, a representative acid sulfate hot spring with low chloride, was chosen to study arsenic geochemistry and microbial community structure using Illumina MiSeq sequencing. Over 0.3 million 16S rRNA sequence reads were obtained from 6-paired parallel water and sediment samples along its outflow channel. Arsenic oxidation occurred in the Zhenxhuquan pool, with distinctly high ratios of arsenate to total dissolved arsenic (0.73–0.86). Coupled with iron and sulfur oxidation along the outflow channel, arsenic accumulated in downstream sediments with concentrations up to 16.44 g/kg and appeared to significantly constrain their microbial community diversity. These oxidations might be correlated with the appearance of some putative functional microbial populations, such as Aquificae and Pseudomonas (arsenic oxidation), Sulfolobus (sulfur and iron oxidation), Metallosphaera and Acidicaldus (iron oxidation). Temperature, total organic carbon and dissolved oxygen significantly shaped the microbial community structure of upstream and downstream samples. In the upstream outflow channel region, most microbial populations were microaerophilic/anaerobic thermophiles and hyperthermophiles, such as Sulfolobus, Nocardia, Fervidicoccus, Delftia, and Ralstonia. In the downstream region, aerobic heterotrophic mesophiles and thermophiles were identified, including Ktedonobacteria, Acidicaldus, Chthonomonas and Sphingobacteria. A total of 72.41–95.91% unassigned-genus sequences were derived from the downstream high arsenic sediments 16S rRNA clone libraries. This study could enable us to achieve an integrated understanding on arsenic biogeochemistry in acid hot springs.

Nutrient removal performance and microbial characteristics of a full-scale IFAS-EBPR process treating municipal wastewater.

This work describes the nutrient removal performance and microbial characteristics of a full-scale integrated fixed-film activated sludge-enhanced biological phosphorus removal (IFAS-EBPR) process for municipal wastewater treatment. The polymerase chain reaction-denaturing gradient gel electrophoresis results showed that the presence of bacteria in this process, including Nitrosomonas sp., Nitrospira sp., Nitrobacter sp., Pseudomonas sp. and Acinetobacter sp., clusters. The fluorescence in situ hybridization results implied that there were more nitrifiers and denitrifiers on the biofilm carriers than in the suspended sludge, whereas more phosphorus-accumulating organisms (PAOs) resided in the suspended sludge. With the cooperation of these functional microbial populations both on the biofilm carriers and in the suspended sludge, the chemical oxygen demand (COD), NH4(+)-N, total nitrogen (TN) and total phosphorus (TP) removal efficiencies were maintained at 84, 97, 70 and 81%, and the effluent concentrations of them averaged 30, 1.0, 11.5 and 0.6 mg/L, which all satisfy the Chinese discharge standard (COD <50 mg/L, NH4(+)-N <5 mg/L, TN <15 mg/L and TP <1 mg/L), respectively. Therefore, the IFAS-EBPR process is a reliable and effective process for nutrient removal.

Performance, carotenoids yield and microbial population dynamics in a photobioreactor system treating acidic wastewater: Effect of hydraulic retention time (HRT) and organic loading rate (OLR)

Effects of hydraulic retention time (HRT) and influent organic loading rate (OLR) were investigated in a photobioreactor containing PNSB (Rhodopseudomonas palustris)-chemoheterotrophic bacteria to treat volatile fatty acid wastewater. Pollutants removal, biomass production and carotenoids yield in different phases were investigated in together with functional microbial population dynamics. The results indicated that properly decreasing HRT and increasing OLR improved the nutrient removal performance as well as the biomass and carotenoids productions. 85.7% COD, 89.9% TN and 91.8% TP removals were achieved under the optimal HRT of 48h and OLR of 2.51g/L/d. Meanwhile, the highest biomass production and carotenoids yield were 2719.3mg/L and 3.91mg/g-biomass respectively. In addition, HRT and OLR have obvious impacts on PNSB and total bacteria dynamics. Statistical analyses indicated that the COD removal exhibited a positive relationship with OLR, biomass and carotenoids production. PNSB/total bacteria ratio had a positive correlation with the carotenoids yield.

Enrichment of functional microbes and genes during pyrene degradation in two different soils

Stimulating microbial degradation is a promising strategy for the remediation of soils contaminated with polycyclic aromatic hydrocarbons (PAHs). To better understand the functional microbial populations and processes involved in pyrene biodegradation in situ, the dynamics of pyrene degradation and functional microbial abundance were monitored during pyrene incubation in soils. We hope our findings will provide new insights into in situ pyrene biodegradation in soils and help to identify functional microbes from soils. Pyrene (60 mg kg−1) was incubated with two different soils, one is lower PAH-containing agricultural soil (LS), and the other is higher PAH-containing industrial soil (HS). During incubation, triplicate samples were collected on days 0, 3, 7, 14, and 35. Pyrene in soil samples was analyzed using an Agilent gas chromatograph (7890A) equipped with a mass-selective detector (model 5897). DNA in soils was extracted with a FastDNA Spin kit for soil (Bio101, USA). The abundance of functional microbes and genes was monitored by a Taqman or SYBR Green based real-time PCR quantification using an iCycler iQ5 themocycler (Bio-Rad, USA). The diversity of PAH-RHDα GP genes was evaluated by constructing clone libraries and sequencing. In both soils, more than 80 % of the added pyrene was degraded within 35 days. After 35-day incubation, there was a significant enrichment of Gram-positive bacteria harboring PAH-ring hydroxylation dioxygenase (PAH-RHDα GP) genes, and the abundance of Mycobacterium increased significantly. In PAH-RHDα GP clone libraries from two soils, Mycobacterium was detected, while most sequences were closely related to uncultured Gram-positive bacteria. In addition, two pyrene catabolic pathways might be involved in pyrene degradation, as pyrene dioxygenase genes, nidA and nidA3, were dramatically enriched during incubation. Moreover, the abundance and diversity of potential degraders in two soils showed significantly difference in responding to pyrene stress. This result indicates that soil condition can significantly affect functional microbial populations and biological process for pyrene biodegradation. These results revealed that Mycobacterium as well as uncultured Gram-positive PAH-RHDα genotypes may be the important group of pyrene degraders in soils, and two pyrene catabolic pathways, targeted by nidA and nidA3, might potentially contribute to in situ biodegradation of pyrene. This study characterized the response pattern of potential pyrene degraders to pyrene stress in two different soils, which would increase our understanding of the indigenous processes of pyrene biodegradation in soil environment.

Heterogeneity of Intracellular Polymer Storage States in Enhanced Biological Phosphorus Removal (EBPR) – Observation and Modeling

A number of agent-based models (ABMs) for biological wastewater treatment processes have been developed, but their skill in predicting heterogeneity of intracellular storage states has not been tested against observations due to the lack of analytical methods for measuring single-cell intracellular properties. Further, several mechanisms can produce and maintain heterogeneity (e.g., different histories, uneven division) and their relative importance has not been explored. This article presents an ABM for the enhanced biological phosphorus removal (EBPR) treatment process that resolves heterogeneity in three intracellular polymer storage compounds (i.e., polyphosphate, polyhydroxybutyrate, and glycogen) in three functional microbial populations (i.e., polyphosphate-accumulating, glycogen-accumulating, and ordinary heterotrophic organisms). Model predicted distributions were compared to those based on single-cell estimates obtained using a Raman microscopy method for a laboratory-scale sequencing batch reactor (SBR) system. The model can reproduce many features of the observed heterogeneity. Two methods for introducing heterogeneity were evaluated. First, biological variability in individual cell behavior was simulated by randomizing model parameters (e.g., maximum acetate uptake rate) at division. This method produced the best fit to the data. An optimization algorithm was used to determine the best variability (i.e., coefficient of variance) for each parameter, which suggests large variability in acetate uptake. Second, biological variability in individual cell states was simulated by randomizing state variables (e.g., internal nutrient) at division, which was not able to maintain heterogeneity because the memory in the internal states is too short. These results demonstrate the ability of ABM to predict heterogeneity and provide insights into the factors that contribute to it. Comparison of the ABM with an equivalent population-level model illustrates the effect of accounting for the heterogeneity in models.

Comparison of Conventional and Integrated Fixed‐Film Activated Sludge Systems: Attached‐ and Suspended‐Growth Functions and Quantitative Polymerase Chain Reaction Measurements

Pilot-scale integrated fixed-film activated sludge (IFAS) and non-IFAS control systems were compared, with respect to overall performance and functional behaviors and microbial population composition in the attached and suspended phases. The suspended phases of the control and IFAS systems exhibited similar rates of ammonia consumption; the attached phase in the second aerobic IFAS reactor had significantly higher rates of ammonia consumption and nitrate production than any other biomass source, and the attached biomass from the first aerobic reactor had the lowest ammonia consumption rates. Quantitative polymerase chain reaction (qPCR) indicated the presence of the ammonia-oxidizing bacteria Nitrosomonas oligotropha and the nitrite-oxidizing bacteria Nitrospira spp. and Nitrobacter spp. Mathematical modeling and qPCR both indicated greater concentrations of nitrifiers in the attached phases of a downstream aerobic reactor relative to the upstream reactor, possibly because of increased competition from heterotrophs for space in the attached phase of the upstream aerobic reactor.