Characteristics of organic pollutants and their effects on the microbial composition and activity in the industrial soils of Pearl River Delta, China.

To investigate the interaction between organic pollutants and soil microorganisms, industrial soils were collected from Pearl River Delta region of China for determining semi-volatile organic pollutants, the community structure and activity of microorganisms. The results showed that polycyclic aromatic hydrocarbons (PAHs) (63.3-4956 µg kg-1) and phthalate esters (PAEs) (272-65,837 µg kg-1) were main organic pollutants in the research area soils. Chemical manufacturing industry and plastics manufacturing industry contributed greatly to PAH pollution and PAE pollution, respectively. Organic pollutants changed the biomass of microorganisms. In most industrial soils, the biomass of actinomycetes was the highest in the industrial soils, followed by G- bacteria, G+ bacteria and fungi. The exception was that the biomass of fungi in the soil near chemical manufacturing industry was greater than that of G+ bacteria. The soil microbial biomass (including soil microbial biomass carbon, soil microbial biomass nitrogen, the biomass of actinomycetes, bacteria, and fungi) and soil enzyme activities (sucrase and urease) positively correlated with the organic pollutant residues, and the microbial species diversity and microbial species abundance decreased with organic pollutant residues increasing. Based on the correlation analysis, the urease activity, actinomycetes biomass, and fungi biomass were appropriate biological indicators for evaluating the stress of organic pollutants. Our research provides a new perspective for understanding the soil biological response in industrial soils.

Contribution of dicarboxylic acids to pyrene biodegradation and transcriptomic responses of Enterobacter sp. PRd5.

The colonization of degrading endophytic bacteria is an effective means to reduce the residues of polycyclic aromatic hydrocarbons (PAHs) in crops. Dicarboxylic acids, as the main active components in crops, can affect the physiological activities of endophytic bacteria and alter the biodegradation process of PAHs in crops. In this study, malonic acid and succinic acid were selected as the representatives to investigate the contribution of dicarboxylic acids to pyrene biodegradation by endophytic Enterobacter sp. PRd5 in vitro. The results showed that dicarboxylic acids improved the biodegradation of pyrene and altered the expression of the functional gene of strain PRd5. Malonic acid and succinic acid reduced the half-life of pyrene by 20.0% and 27.8%, respectively. The degrading enzyme activities were significantly stimulated by dicarboxylic acids. There were 386 genes up-regulated and 430 genes down-regulated in strain PRd5 with malonic acid, while 293 genes up-regulated and 340 genes down-regulated with succinic acid. Those up-regulated genes were distributed in the functional classification of signal transduction, membrane transport, energy metabolism, carbohydrate metabolism, and amino acid metabolism. Malonic acid mainly enhanced the central carbon metabolism, cell proliferation, and cell activity. Succinic acid mainly improved the expression of degrading gene. Overall, the findings of this study provide new insights into the regulation and control of PAH stress by crops. KEY POINTS: • Dicarboxylic acids improved the biodegradation of pyrene by Enterobacter sp. PRd5. • The degrading enzyme activities were stimulated by dicarboxylic acids. • There are different facilitation mechanisms between malonic acid and succinic acid.

[Colonization performance and pyrene degradation characteristics of Stenotrophomonas maltophilia PX1]. / å—œéº¦èŠ½å¯¡å »å•èƒžèŒPX1的降解芘特性及定殖效能.

We screened and identified an endophytic bacterium that could efficiently degrade PAHs, which would expand the library of polycyclic aromatic hydrocarbons (PAHs) degrading microorganisms and reduce the pollution risk of crops. Its degradation mechanism and colonization performance were preliminarily examined. The results showed that strain PX1 belonged to Stenotrophomonas maltophilia. The strain had broad spectrum ability to remove PAHs. In PAH mineral salt (MS) media, almost 100% naphthalene was degraded by strain PX1 after 7-d incubation. In a cultivation system solely containing phenanthrene of 50.0 mg·L-1, pyrene of 20.0 mg·L-1, fluoranthene of 20.0 mg·L-1 or benzo[a]pyrene of 10.0 mg·L-1, the degradation efficiency of phenanthrene, pyrene, fluoranthene and benzo[a]pyrene by strain PX1 reached 72.6%, 50.7%, 31.9%, and 12.9%, respectively. Pyrene was selected as PAHs model to study the degradation characteristics of strain PX1. Enzyme activity tests showed that the activities of phthalate dioxygenase, catechol-1,2-dioxygenase, and catechol-2,3-dioxygenase in strain PX1 were induced by pyrene. Some metabolic intermediates such as 4,5-epoxypyrene, 4,5-dihydroxypyrene, gentilic acid/protocatechuic acid, salicylic acid, cis-hexadienedioic acid/2-hydroxymyxofuroic acid semialdehyde, cis-2'-carboxyphenylpyruvic acid, 1-hydroxy-2-naphthoic acid, and salicylaldehyde were detected during the degradation of pyrene by strain PX1. Results of the seed soaking experiment showed that strain PX1 could efficiently colonize in Ipomoea aquatic and Triticum aestivum. After inoculated with strain PX1, the growth of I. aquatic and T. aestivum was significantly increased, and the pyrene concentration in I. aquatic, T. aestivum and MS media was reduced by 29.8%-50.7%, 52.4%-67.1% and 8.0%-15.3%, respectively. Our results suggested that strain PX1 degraded pyrene mainly through 'salicylate pathway' and 'phthalate pathway', and could be colonized into plants and promote plant growth.

Effects of amino-modified biofilm carriers on biogas production in the anaerobic digestion of corn straw.

This paper studied the property of three different biofilm carriers added into the anaerobic digestion systems, a granular activated carbon, a polyacrylonitrile, and a polyacrylonitrile modified with diethylenetriamine (PAN-NH2). The PAN-NH2 system kept the maximum biogas and methane production, which were 42.69% and 37.29% higher than the control system, respectively. The value of pH and chemical oxygen demand, the content of total solid and volatile solid, volatile fatty acids concentration, coenzyme F420 concentration, and microbial community analysis were investigated during the anaerobic digestion process. The PAN-NH2 system had the highest removal efficiency of the pollutants and regulated the pH of the system better than other systems. The result of high-throughput sequencing analysis showed that the addition of biofilm carriers and mediation with amino-groups adjusted system pH and improved biogas and CH4 production by reducing the relative abundance of bacteria in the hydrolysis/acidogenesis stages. Methanosarcina gradually replaced other methanogens during the experimental runs and was the dominant methanogen at the end of the anaerobic digestion process.

Anaerobic biodegradation of pyrene by Klebsiella sp. LZ6 and its proposed metabolic pathway.

Pyrene is one of the polycyclic aromatic hydrocarbons, which are a potential threat to ecosystems due to their mutagenicity, carcinogenicity, and teratogenicity. In this study, several bacteria were isolated from oil contaminated sludge and their capacity to biodegrade pyrene was investigated. Of these bacteria, the monoculture strain LZ6 showed the highest pyrene anaerobic biodegradation rate of 33% after 30 days when the initial concentration was 50 mg/L, and was identified as Klebsiella sp. LZ6 by morphological observation, the GENIII technology of Biolog, and 16S rDNA gene sequence analysis. The influence of various culture parameters on the biodegradation of pyrene were evaluated, and Klebsiella sp. LZ6 all showed the high degradation rate at an inoculum of 10-20% (v/v), pH 6.0-8.4, temperature 30-38°C, and initial pyrene concentration of 50-150 mg/L. The intermediate metabolites of the anaerobic biodegradation were analyzed by GC-MS. Several metabolites were identified, such as pyrene, 4,5-dihydro-, phenanthrene, dibenzo-p-dioxin, and 4-hydroxycinnamate acid. The anaerobic metabolic pathway for the degradation of pyrene was inferred by the products. It seems that pyrene was first reduced to pyrene,4,5-dihydro- by the adding of two hydrogen atoms, and then the carbon-carbon bond cleavage at saturated carbon atoms generated phenanthrene.