Xiao Kong

Biodegradation of Di-n-Butyl Phthalate by a Newly Isolated Halotolerant Sphingobium sp.

A Gram-negative strain (TJ) capable of growing aerobically on mixed phthalate esters (PAEs) as the sole carbon and energy source was isolated from the Haihe estuary, Tianjin, China. It was identified as belonging to the Sphingobium genus on the basis of morphological and physiological characteristics and 16S rRNA and gyrb gene sequencing. The batch tests for biodegradation of di-n-butyl phthalate (DBP) by the Sphingobium sp. TJ showed that the optimum conditions were 30 °C, pH 7.0, and the absence of NaCl. Stain TJ could tolerate up to 4% NaCl in minimal salt medium supplemented with DBP, although the DBP degradation rates slowed as NaCl concentration increased. In addition, substrate tests showed that strain TJ could utilize shorter side-chained PAEs, such as dimethyl phthalate and diethyl phthalate, but could not metabolize long-chained PAEs, such as di-n-octyl phthalate, diisooctyl phthalate, and di-(2-ethyl-hexyl) phthalate. To our knowledge, this is the first report on the biodegradation characteristics of DBP by a member of the Sphingobium genus.

Biodegradation of di-n-Butyl Phthalate by Achromobacter sp. Isolated from Rural Domestic Wastewater

A bacterial strain W-1, isolated from rural domestic wastewater, can utilize the environmental hormone di-n-butyl phthalate (DBP) as the sole carbon and energy source. The isolated bacterium species was confirmed to belong to the genus Achromobacter based on its 16S rRNA gene sequence. The results of substrate utilization tests showed that the strain W-1 could utilize other common phthalates and phenol. High-performance liquid chromatography analysis revealed that the optimal conditions for DBP degradation were pH 7.0, 35 °C, and an agitation rate of 175 rpm. Under these conditions, 500 mg/L of DBP was completely degraded within 30 h. The effects of heavy metals (50 mg/L Cu2+ and 500 mg/L Pb2+) and surfactants (100 mg/L SDS and 500 mg/L Tween 20) on DBP degradation were investigated. The results demonstrated that Cu2+ and SDS severely inhibited DBP degradation and Pb2+ weakly inhibited DBP degradation, while Tween 20 greatly enhanced DBP degradation. Furthermore, phthalate degradation genes were found to be located on a plasmid present in Achromobacter sp. W-1.

Characterization and Genomic Analysis of a Highly Efficient Dibutyl Phthalate-Degrading Bacterium Gordonia sp. Strain QH-12

A bacterial strain QH-12 isolated from activated sludge was identified as Gordonia sp. based on analysis of 16S rRNA gene sequence and was found to be capable of utilizing dibutyl phthalate (DBP) and other common phthalate esters (PAEs) as the sole carbon and energy source. The degradation kinetics of DBP under different concentrations by the strain QH-12 fit well with the modified Gompertz model (R2 > 0.98). However, strain QH-12 could not utilize the major intermediate product phthalate (phthalic acid; PA) as the sole carbon and energy source, and only a little amount of PA was detected. The QH-12 genome analysis revealed the presence of putative hydrolase/esterase genes involved in PAEs-degradation but no phthalic acid catabolic gene cluster was found, suggesting that a novel degradation pathway of PAEs was present in Gordonia sp. QH-12. This information will be valuable for obtaining a more holistic understanding on diverse genetic mechanisms of PAEs-degrading Gordonia sp. strains.

Pumpkin powdery mildew disease severity influences the fungal diversity of the phyllosphere

Phyllosphere microbiota play a crucial role in plant-environment interactions and their microbial community and function are influenced by biotic and abiotic factors. However, there is little research on how pathogens affect the microbial community of phyllosphere fungi. In this study, we collected 16 pumpkin (Cucurbita moschata) leaf samples which exhibited powdery mildew disease, with a severity ranging from L1 (least severe) to L4 (most severe). The fungal community structure and diversity was examined by Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of ribosomal RNA genes. The results showed that the fungal communities were dominated by members of the Basidiomycota and Ascomycota. The Podosphaera was the most dominant genus on these infected leaves, which was the key pathogen responsible for the pumpkin powdery mildew. The abundance of Ascomycota and Podosphaera increased as disease severity increased from L1 to L4, and was significantly higher at disease severity L4 (P < 0.05). The richness and diversity of the fungal community increased from L1 to L2, and then declined from L2 to L4, likely due to the biotic pressure (i.e., symbiotic and competitive stresses among microbial species) at disease severity L4. Our results could give new perspectives on the changes of the leaf microbiome at different pumpkin powdery mildew disease severity.

Chitinophaga caeni sp. nov., isolated from activated sludge

A novel Gram-stain-negative, non-motile, non-spore-forming, rod-shaped, strictly aerobic bacterium, designated strain 13T, was isolated from an activated sludge wastewater treatment plant in Beijing, China. 16S rRNA gene sequence analysis placed this organism within the genus Chitinophaga of the class Bacteroidetes, with Chitinophaga skermanii CC-SG1B (92.4 % gene sequence similarity) and Chitinophaga rupis CS5-B1 (91.2 %) as its closest relatives. This isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and the whole-cell hydrolysate was ribose. Phosphatidylethanolamine was the predominant polar lipid. The major cellular fatty acids were iso-C15 : 0, C16 : 1ω5c and iso-C17 : 0 3-OH. Menaquinone-7 was the only isoprenoid quinone present. The complete genome of the novel strain was sequenced; the size of the genome was 5.28 Mb and the genomic DNA G+C content was 42.5 mol%. The phenotypic, chemotaxonomic and phylogenetic data showed that strain 13T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga caeni sp. nov. is proposed. The type strain is 13T (=CICC 24262T=KCTC 62265T).

Gordonia phthalatica sp. nov., a di-n-butyl phthalate-degrading bacterium isolated from activated sludge

A phthalate esters-degrading bacterial strain, designated QH-11T, was isolated from an activated sludge wastewater treatment plant in Beijing, PR China. The cells were aerobic, Gram-stain-positive, non-motile, catalase-positive, oxidase-negative, short rods and formed white colonies on trypticase soy agar. This isolate contained meso-diaminopimelic acid as the diagnostic diamino acid and whole-cell hydrolysates contained arabinose and ribose. Diphosphatidylglycerol and phosphatidylethanolamine were the predominant polar lipids. According to the results of full-length of 16S rRNA gene sequence analysis, QH-11T represented a member of the genus Gordonia and showed the highest sequence similarity to Gordonia hydrophobica DSM 44015T (99.2 %), but was distinguishable by a low level of DNA-DNA relatedness (37.8 %). Genome-based comparisons indicated a clear distinction from the top ten most similar type strains (16S rRNA gene sequence) with pairwise average nucleotide identities (ANI) between 74.6 and 83.4 %. The predominant respiratory quinone was MK-9(H2), the mycolic acids present had 56 to 62 carbon atoms, and the major fatty acids were C16 : 0 (33.3 %), C17 : 1ω8c (23.4 %) and C18 : 1ω9c (17.9 %). The DNA G+C content was 68.0 mol%. On the basis of the results of DNA-DNA hybridization, ANI and physiological and biochemical tests, it is proposed that QH-11T represents a novel species of the genus Gordonia, for which the name Gordonia phthalatica sp. nov. is proposed. The type strain is QH-11T (CICC 24107T =KCTC 39933T).

Dibutyl phthalate contamination remolded the fungal community in agro-environmental system

Dibutyl phthalate (DBP) is a typical soil contaminant that is widely used as plasticizer in modern agricultural production. In this study, an experiment was conducted to evaluate fungal community succession in a soil-vegetable ecosystem under different DBP concentrations. By using high-throughput sequencing of the ribosomal internal transcribed spacer (ITS) region, it was shown that DBP contamination caused significant changes to the soil fungal community, in terms of both α and β diversities. The largest changes in fungal α and β diversities were detected under 50 mg/kg DBP concentration at the first day of addition. The bulk soils, rhizosphere soils and the phyllosphere harbored different fungal communities, while the abundance of saprotrophs and plant pathogens in the phyllosphere have been increased under DBP contamination. From correlation analysis and partial Mantel test, the change in fungal community α diversity was the result of multiple factors (DBP concentration, bacterial community and soil properties) while the β diversity of fungal community was mainly co-varied with the bacterial community after DBP contamination. Moreover, molecular ecological network analysis demonstrated that DBP contamination was detrimental to mutualistic relationships among fungal species and destabilized the network structure. Overall, the fungal communities in soils and around vegetables were largely remolded by DBP contamination that provides new insight into DBP contamination impacts on agricultural ecosystems.

Bacterial communities and potential waterborne pathogens within the typical urban surface waters

Waterborne pathogens have attracted a great deal of attention in the public health sector over the last several decades. However, little is known about the pathogenic microorganisms in urban water systems. In this study, the bacterial community structure of 16 typical surface waters in the city of Beijing were analyzed using Illumina MiSeq high-throughput sequencing based on 16S rRNA gene. The results showed that Bacteroidetes, Proteobacteria and Actinobacteria were the dominant groups in 16 surface water samples, and Betaproteobacteria, Alphaproteobacteria, Flavobacteriia, Sphingobacteriia and Actinobacteria were the most dominant classes. The dominant genus across all samples was Flavobacterium. In addition, fifteen genus level groups of potentialy pathogenic bacteria were detected within the 16 water samples, with Pseudomonas and Aeromonas the most frequently identified. Spearman correlation analysis demonstrated that richness estimators (OTUs and Chao1) were correlated with water temperature, nitrate and total nitrogen (p < 0.05), while ammonia-nitrogen and total nitrogen were significantly correlated with the percent of total potential pathogens (p ≤ 0.05). These results could provide insight into the ecological function and health risks of surface water bacterial communities during the process of urbanization.

Responses of bacterial community to dibutyl phthalate (DBP) pollution in a soil-vegetable ecosystem

Phthalate esters (PAEs) are a type of plasticizer that has aroused great concern due to their mutagenic, teratogenic, and carcinogenic effects, wherefore dibutyl phthalate (DBP) and other PAEs have been listed as priority pollutants. In this study, the impacts of DBP on a soil-vegetable ecosystem were investigated. The results showed that DBP could accumulate within vegetable tissues, and the accumulative effect was enhanced with higher levels of DBP contamination in soils. DBP accumulation also decreased vegetable quality in various ways, including decreased soluble protein content and increased nitrate content. The diversity of bacteria in soils gradually decreased with increasing DBP concentration, while no clear association with endophytic bacteria was observed. Also, the relative abundance, structure, and composition of soil bacterial communities underwent successional change during the DBP degradation period. The variation of bulk soil bacterial community was significantly associated with DBP concentration, while changes in the rhizosphere soil bacteria community were significantly associated with the properties of both soil and vegetables. The results indicated that DBP pollution could increase the health risk from vegetables and alter the biodiversity of indigenous bacteria in soil-vegetable ecosystems, which might further alter ecosystem functions in agricultural fields.

Patulibacter brassicae sp. nov., isolated from rhizosphere soil of Chinese cabbage (Brassica campestris).

A novel actinobacterial strain, designated SDT, was isolated from rhizosphere soil of Chinese cabbage in Shandong province, China. The cells were aerobic, Gram-staining-positive, oxidase- and catalase-positive, short rods and formed white colonies on trypticase soy agar. The cell-wall peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid and alanine, glutamic acid and leucine. Diphosphatidylglycerol was the predominant polar lipid. The predominant cellular fatty acid was C18 : 1ω9c; minor components were anteiso-C15 : 0 and anteiso-C17 : 0. The only isoprenoid quinone was demethylmenaquinone 7 (DMK-7), and the DNA G+C content was 72.7 mol%. Based on the full-length 16S rRNA gene sequence analysis, the closest phylogenetic neighbours of strain SDT were Patulibacter medicamentivorans DSM 25962T (96.9 %), Patulibacter minatonensis DSM 18081T (96.7 %), Patulibacter americanus DSM 16676T (96.2 %) and Patulibacter ginsengiterrae DSM 25990T (95.9 %). Considering combined phenotypic and genotypic characteristics, it is proposed that strain SDT represents a novel species of the genus Patulibacter, for which the name Patulibacter brassicae sp. nov. is proposed. The type strain is SDT (=CICC 24108T=KCTC 39817T).