Producers and drivers of odor compounds in a large drinking-water source

IntroductionTaste and odor (T&O) problems have been affecting drinking water safety. As a eutrophicated drinking water reservoir in Tianjin city, the Yuqiao Reservoir was threatened by 2-MIB and geosmin in recent years.MethodsIn this study, quantile regression analysis and metagenome were used to quickly and accurately screen the producers and drivers of 2-MIB and geosmin in this reservoir.ResultsThe mean concentrations of 2-MIB and geosmin in the four-year were 103.58 ± 128.13 ng/L and 14.29 ± 27.95 ng/L, respectively. 2-MIB concentrations were higher in summer and autumn, with a bimodal variation throughout the year. Geosmin concentrations showed a decreasing trend from year to year from 2018 to 2021. Metagenome revealed that Pseudanabaena sp. dqh15, Microcoleus pseudautumnalis Ak1609, Pseudanabaena limnetica, and Planktothricoides raciborskii were the 2-MIB-producers, while Streptosporangium caverna and Dolichospermum circinale were the geosmin-producers. Multivariate quantile regression analysis indicated Pseudanabaena sp. and CODMn were the best predictors of 2-MIB concentrations, temperature and CODMn were the most useful parameters for describing geosmin concentration change. 2-MIB concentrations increased with the increase of Pseudanabaena sp. cell density and CODMn. Geosmin concentrations were higher at harsh temperatures and increased with higher CODMn. CODMn was significantly and positively correlated with the biosynthesis of secondary metabolites synthesis and terpenoid backone biosynthesis pathway. Both quantile regression and metagenome results showed that CODMn was an important driver of odor compounds.DiscussionMetagenome achieved higher resolution of taxonomic annotation than amplicons to identify odor-producers, which helps us to understand the main taxa of odor-producing microorganisms in Chinese water bodies and the genetic basis of odor compounds in microorganisms. Understanding the sources and drivers of odor compounds was useful for improving taste and odor problem management. This is the first time that the main odor-producing microorganisms in water bodies have been resolved by microbial metagenomic functional gene prediction

Water quality variation in the middle route of South-to-North Water Diversion Project, China

The South-to-North Water Division Middle Route Project (MRP) is currently the longest inter-basin water diversion project in the world. It benefits a large population and its water quality has attracted much attention. In this study, seasonal investigations on 11 sampling sites along the MRP were conducted from 2018 to 2019; water temperature, pH, turbidity, transparency, CODMn, dissolved oxygen, total phosphorus, phosphate, total nitrogen, ammonia, nitrate, and chlorophyll a were determined synchronously. Single leakage distance clustering analysis identified the spatio-seasonal heterogeneity of physiochemical parameters. The trophic level index (TLI) and the water quality status were assessed: TLI increased and WQI decreased from south to north; TLI and WQI had seasonal differences (p < 0.001), the best water quality was observed in autumn, and the lowest TLI was observed in winter. The trophic level was “oligotrophic to mesotrophic”; water quality status was “good.” The multiple linear stepwise regression analysis confirmed that total nitrogen (TN), Chl a, and CODMn were the driving factors in water quality. These factors were applied to build the simplified WQI model, which was confirmed as a reliable method of water quality assessment for the MRP and a fitting substitute for TLI and WQI. The results provided support for the water quality evaluation of the MRP

Antibiofilm Activity of an Exopolysaccharide from Marine Bacterium Vibrio sp. QY101

Bacterial exopolysaccharides have always been suggested to play crucial roles in the bacterial initial adhesion and the development of complex architecture in the later stages of bacterial biofilm formation. However, Escherichia coli group II capsular polysaccharide was characterized to exert broad-spectrum biofilm inhibition activity. In this study, we firstly reported that a bacterial exopolysaccharide (A101) not only inhibits biofilm formation of many bacteria but also disrupts established biofilm of some strains. A101 with an average molecular weight of up to 546 KDa, was isolated and purified from the culture supernatant of the marine bacterium Vibrio sp. QY101 by ethanol precipitation, iron-exchange chromatography and gel filtration chromatography. High performance liquid chromatography traces of the hydrolyzed polysaccharides showed that A101 is primarily consisted of galacturonic acid, glucuronic acid, rhamnose and glucosamine. A101 was demonstrated to inhibit biofilm formation by a wide range of Gram-negative and Gram-positive bacteria without antibacterial activity. Furthermore, A101 displayed a significant disruption on the established biofilm produced by Pseudomonas aeruginosa, but not by Staphylococcus aureus. Importantly, A101 increased the aminoglycosides antibiotics' capability of killing P. aeruginosa biofilm. Cell primary attachment to surfaces and intercellular aggregates assays suggested that A101 inhibited cell aggregates of both P. aeruginosa and S. aureus, while the cell-surface interactions inhibition only occurred in S. aureus, and the pre-formed cell aggregates dispersion induced by A101 only occurred in P. aeruginosa. Taken together, these data identify the antibiofilm activity of A101, which may make it potential in the design of new therapeutic strategies for bacterial biofilm-associated infections and limiting biofilm formation on medical indwelling devices. The found of A101 antibiofilm activity may also promote a new recognition about the functions of bacterial exopolysaccharides

Classification of ETM+ Remote Sensing Image Based on Hybrid Algorithm of Genetic Algorithm and Back Propagation Neural Network

The back propagation neural network (BPNN) algorithm can be used as a supervised classification in the processing of remote sensing image classification. But its defects are obvious: falling into the local minimum value easily, slow convergence speed, and being difficult to determine intermediate hidden layer nodes. Genetic algorithm (GA) has the advantages of global optimization and being not easy to fall into local minimum value, but it has the disadvantage of poor local searching capability. This paper uses GA to generate the initial structure of BPNN. Then, the stable, efficient, and fast BP classification network is gotten through making fine adjustments on the improved BP algorithm. Finally, we use the hybrid algorithm to execute classification on remote sensing image and compare it with the improved BP algorithm and traditional maximum likelihood classification (MLC) algorithm. Results of experiments show that the hybrid algorithm outperforms improved BP algorithm and MLC algorithm

Genotypes of ITS region of rRNA in Microcystis (Cyanobacteria) populations in Erhai Lake (China) and their correlation with eutrophication level

Previous studies on spatiotemporal changes of Microcystis genotypes have shown that the existence and succession of dominant genotypes always occur in eutrophicated freshwater bodies. However, few studies have focused on the correlation between genotype composition and eutrophication level. In the present study, clone libraries of the internal transcribed spacer (ITS) of rrn operon were sequenced from Microcystis populations in Erhai Lake, a subtropical plateau lake in the preliminary eutrophication stage. The genotype composition of the Microcystis populations was highly variable at spatiotemporal scales, and 473 ITS genotypes were identified from the 800 ITS sequences obtained. However, no significantly dominant ITS genotypes existed in the lake. Comparison of Erhai Lake with four major lakes in China, namely, Taihu, Chaohu, Gucheng, and Shijiu Lakes, showed that the Microcystis ITS genotypes and genetic diversity were negatively correlated with eutrophication level. Extensive comparison of the Microcystis ITS genotypes from waters worldwide revealed that 440 ITS genotypes were unique to Erhai Lake, and no obvious phylogenetic correlations can be detected among the dominant genotypes from different water bodies. The high genetic diversity of the Microcystis populations in Erhai Lake may have resulted from the effect of the early stage of eutrophication

Optimization method for Microcystis bloom mitigation by hydrogen peroxide and its stimulative effects on growth of chlorophytes

Hydrogen peroxide (HP) is a feasible algicide to control cyanobacterial blooms, but its application in the waters with strong reductive power is still a problem. The rapid decomposition rate of HP results in a short residence time in the waters, which renders the failure of bloom mitigation. In this study, the damage of Microcystis aeruginosa (M. aeruginosa) by HP, the optimization method for Microcystis bloom control and its field effects were investigated. Results of microcosm experiments indicated M. aeruginosa was vulnerable to HP. The HP-induced damage was mainly attributed to the impairments of HP detoxification pathways and photosystem. Repetitive additions of HP, which could prolong the residence time, were conducted in the mesocosm experiments. HP concentration ranged from 96 mu M to 165 mu M for 2 h could successfully mitigate Microcystis bloom, even though HP decomposition rate reached 109 mu M per h. Besides the removal of M. aeruginosa, contents of total dissolved nitrogen, total dissolved phosphate, dissolved organic carbon and chromophoric dissolved organic matter in water column increased significantly (p < 0.05). The enrichment of nutrients promoted the growth of chlorophytes but the growth of M. aeruginosa couldn't be observed. The dominant species thrived in the HP-treated waters was Chlamydomonas sp. Results in this study confirmed that HP was a promising algicide for cyanobacterial blooms control. The optimization method further demonstrated that repetitive additions of HP could favor the mitigation of cyanobacterial blooms. (C) 2019 Elsevier Ltd. All rights reserved

Environmental Factors Drive Periphytic Algal Community Assembly in the Largest Long-Distance Water Diversion Channel

Periphytic algae exist widely in different waters. However, little is known about periphytic algae in long-distance water diversion channels across watersheds. We investigated the periphytic algae and the environmental factors at twenty sampling sites in the middle route of the South-to-North Water Diversion Project (MRP). The dominant species were Desmodesmus intermedius (Hegewald), Calothrix thermalis (Bornet & Flahault), Calothrix parietina (Bornet & Flahault) and Leptolyngbya benthonica (Anagnostidis) (dominance > 0.02) as measured in a whole year. Habitat heterogeneity in the MRP led to lower spatial heterogeneity and higher temporal heterogeneity of the periphytic algal community. Stochastic processes are the major process in periphytic community assembly. In deterministic processes, homogeneous selection had the major role in structuring the periphytic community, whereas the role of heterogeneous selection was less significant. In stochastic processes, dispersal limitations had the major role in structuring the periphytic community, whereas the role of homogenizing dispersal and drift were less significant. The variation in total nitrogen and total phosphorus promoted more stochastic processes (−1.96 1.96). In integrating all of this empirical evidence, we explore the role of environmental factors in the action of ecological processes shaping thecommunity assembly of the periphytic algal community

Revealing Cryptic Changes of Cyanobacterial Community Structure in Two Eutrophic Lakes Using eDNA Sequencing

Harmful cyanobacterial blooms pose a risk to human health worldwide. To enhance understanding on the bloom-forming mechanism, the spatiotemporal changes in cyanobacterial diversity and composition in two eutrophic lakes (Erhai Lake and Lushui Reservoir) of China were investigated from 2010 to 2011 by high-throughput sequencing of environmental DNA. For each sample, 118 to 260cpcBA-IGS operational taxonomic units (OTUs) were obtained. Fifty-two abundant OTUs were identified, which made up 95.2% of the total sequences and were clustered into nine cyanobacterial groups. Although the cyanobacterial communities of both lakes were mainly dominated byMicrocystis, Erhai Lake had a higher cyanobacterial diversity. The abundance of mixed Nostocales species was lower than that ofMicrocystis, whereasPhormidiumandSynechococcuswere opportunistically dominant. The correlation between the occurrence frequency and relative abundance of OTUs was poorly fitted by the Sloan neutral model. Deterministic processes such as phosphorus availability were shown to have significant effects on the cyanobacterial community structure in Erhai Lake. In summary, theMicrocystis-dominated cyanobacterial community was mainly affected by the deterministic process. Opportunistically dominant species have the potential to replaceMicrocystisand form blooms in eutrophic lakes, indicating the necessity to monitor these species for drinking water safety

Variation of Microcystis and microcystins coupling nitrogen and phosphorus nutrients in Lake Erhai, a drinking-water source in Southwest Plateau, China

Lake Erhai is the second largest lake of Southwest China and an important drinking water source. The lake is currently defined as the preliminary stage of eutrophic states, but facing a serious threat with transfer into intensive eutrophication. The present study examined the dynamics of Microcystis blooms and toxic Microcystis in Lake Erhai during 2010, based on quantitative real-time PCR method using 16S rRNA gene specific for Microcystis and microcystin systhesis gene (mcy), and chemical analysis on microcystin (MC) concentrations. Total Microcystis cell abundance at 16 sampling sites were shown as an average of 1.7 x 10(7) cells l(-1) (1.3 x 10(2)-3.8 x 10(9) cells l(-1)). Microcystin LR (MC-LR) and microcystin RR (MC-RR) were the main variants. The strong southwesterly winds, anticlockwise circular flows and geographical characteristics of lake and phytoplankton community succession impacted the distribution patterns of Chl a and MC in the lake. The concentration of Chl a and MC and abundances of total Microsytis and MC-producing Microsystis (MCM) were shown to be positively correlated with pH, DO and TP, negatively correlated with SD, NO3-N, TN/Chl a and TN/TP, and not correlated with NH4-N, TN, dissolved total nitrogen (DTN) and water temperatures. When TN/TP decrease, Microcystis tended to dominate and MC concentrations tended to increase, suggesting that the "TN/TP rule" can be partially applied to explain the correlation between the cyanobacterial blooms and nutrients N and P only within a certain nutrient level. It is speculated that N and P nutrients and the associated genes (e.g., mcy) may jointly drive MC concentration and toxigenicity of Microcystis in Lake Erhai