Agromyces chromiiresistens sp. nov., Novosphingobium album sp. nov., Sphingobium arseniciresistens sp. nov., Sphingomonas pollutisoli sp. nov., and Salinibacterium metalliresistens sp. nov.: five new members of Microbacteriaceae and Sphingomonadaceae from polluted soil.

There are many unidentified microbes in polluted soil needing to be explored and nominated to benefit the study of microbial ecology. In this study, a taxonomic research was carried out on five bacterial strains which were isolated and cultivated from polycyclic aromatic hydrocarbons, and heavy metals polluted soil of an abandoned coking plant. Phylogenetical analysis showed that they belonged to the phyla Proteobacteria and Actinobacteria, and their 16S rRNA gene sequence identities were lower than 98.5% to any known and validly nominated bacterial species, suggesting that they were potentially representing new species. Using polyphasic taxonomic approaches, the five strains were classified as new species of the families Microbacteriaceae and Sphingomonadaceae. Genome sizes of the five strains ranged from 3.07 to 6.60 Mb, with overall DNA G+C contents of 63.57-71.22 mol%. The five strains had average nucleotide identity of 72.38-87.38% and digital DNA-DNA hybridization of 14.0-34.2% comparing with their closely related type strains, which were all below the thresholds for species delineation, supporting these five strains as novel species. Based on the phylogenetic, phylogenomic, and phenotypic characterizations, the five novel species are proposed as Agromyces chromiiresistens (type strain H3Y2-19aT = CGMCC 1.61332T), Salinibacterium metalliresistens (type strain H3M29-4T = CGMCC 1.61335T), Novosphingobium album (type strain H3SJ31-1T = CGMCC 1.61329T), Sphingomonas pollutisoli (type strain H39-1-10T = CGMCC 1.61325T), and Sphingobium arseniciresistens (type strain H39-3-25T = CGMCC 1.61326T). Comparative genome analysis revealed that the species of the family Sphingomonadaceae represented by H39-1-10T, H39-3-25T, and H3SJ31-1T possessed more functional protein-coding genes for the degradation of aromatic pollutants than the species of the family Microbacteriaceae represented by H3Y2-19aT and H3M29-4T. Furthermore, their capacities of resisting heavy metals and metabolizing aromatic compounds were investigated. The results indicated that strains H3Y2-19aT and H39-3-25T were robustly resistant to chromate (VI) and/or arsenite (III). Strains H39-1-10T and H39-3-25T grew on aromatic compounds, including naphthalene, as carbon sources even in the presence of chromate (VI) and arsenite (III). These features reflected their adaptation to the polluted soil environment.

Soil microbiomes divergently respond to heavy metals and polycyclic aromatic hydrocarbons in contaminated industrial sites.

Contaminated sites from electronic waste (e-waste) dismantling and coking plants feature high concentrations of heavy metals (HMs) and/or polycyclic aromatic hydrocarbons (PAHs) in soil. Mixed contamination (HMs + PAHs) hinders land reclamation and affects the microbial diversity and function of soil microbiomes. In this study, we analyzed HM and PAH contamination from an e-waste dismantling plant and a coking plant and evaluated the influences of HM and PAH contamination on soil microbiomes. It was noticed that HMs and PAHs were found in all sites, although the major contaminants of the e-waste dismantling plant site were HMs (such as Cu at 5,947.58 ± 433.44 mg kg-1, Zn at 4,961.38 ± 436.51 mg kg-1, and Mn at 2,379.07 ± 227.46 mg kg-1), and the major contaminants of the coking plant site were PAHs (such as fluorene at 11,740.06 ± 620.1 mg kg-1, acenaphthylene at 211.69 ± 7.04 mg kg-1, and pyrene at 183.14 ± 18.89 mg kg-1). The microbiomes (diversity and abundance) of all sites were determined via high-throughput sequencing of 16S rRNA genes, and redundancy analysis was conducted to investigate the relations between soil microbiomes and contaminants. The results showed that the microbiomes of the contaminated sites divergently responded to HMs and PAHs. The abundances of the bacterial genera Sulfuritalea, Pseudomonas, and Sphingobium were positively related to PAHs, while the abundances of the bacterial genera Bryobacter, Nitrospira, and Steroidobacter were positively related to HMs. This study promotes an understanding of how soil microbiomes respond to single and mixed contamination with HMs and PAHs.

Structural insights into the substrate specificity of 5-chloro-2-hydroxymuconate tautomerase CnbG.

The catechol meta-cleavage pathway is widely involved in the degradation of aromatic compounds, including those halogenated aromatic hydrocarbons and their derivatives. CnbG is a kind of 4-oxalocrotonate tautomerase (4-OT) located in the catechol meta-cleavage pathway, catalyzes the ketonization of cis,cis-5-chloro-2-hydroxymuconate and cis,cis-2-hydroxymuconate to yield 5-chloro-2-oxo-3-hexene-1,6-dioate and 2-oxo-3-hexene-1,6-dioate, and contributes to the degradation of 4-chloronitrobenzene and chlorobenzene in Comamonas testosteroni CNB-1. Yet, the reason why CnbG and those 4-OTs could recognize various substrates is not well explained. Here, we determined the crystal structure of CnbG at resolution of 2.0 Å and identified that the potential substrate pocket involved in four conserved residues, residues Pro1, Arg11, Arg39 and Trp50, but not five conserved residues as those reported in other 4-OTs. We also found the four conserved residues assemble different sequence patterns in different 4-OTs, indicating their potential roles in catalysis and substrate binding. Via molecular docking, we found the 5-chloro group was clamped by two residues and extended to the solvent, indicating a substrate binding mode that could bear the substitution of different groups in the 5-position. Our work extends the knowledge of the substrate specificity of enzymes in the catechol meta-cleavage pathway.

The Mediating Role of Psychological Capital on the Association between Occupational Stress and Job Satisfaction among Township Cadres in a Specific Province of China: A Cross-Sectional Study.

Background: Township cadres, considered as basic executors of state policy, play an important role in Chinese society. Their job satisfaction is a vital issue for township management, but there are few studies on this topic in China. The goal of this study is to analyze the relationship between occupational stress and job satisfaction, and to further examine whether psychological capital (PsyCap) can serve as a mediator between stress and job satisfaction in Chinese township cadres. Methods: A cross-sectional survey was carried out during the period of from October 2015 to January 2016 in Liaoning Province of China. The questionnaires, which consisted of an effort-reward imbalance scale, Minnesota Satisfaction Questionnaire (MSQ) for job satisfaction, and the psychological capital questionnaire (PCQ-24), as well as questions about demographic characteristics, were distributed to 1800 township cadres and complete responses were received from 1525 participants. Structural equation modeling was used to examine the role that psychological capital played in mediating between occupational stress and job satisfaction. Results: In the present study, effort-reward ratio (ERR= 11 × effort/6 × reward) was negatively associated with job satisfaction (r = -0.372, p < 0.001), whereas psychological capital was positively associated with job satisfaction in township cadres (r = 0.587, p < 0.001) from a specific province in China. Psychological capital is a mediator between the association of job stress and job satisfaction. Conclusions: Psychological capital partially mediated the relationship between job stress and job satisfaction among Chinese township cadres. Interventions to improve Chinese township cadres' job satisfaction should be developed in the future, especially the enhancement of PsyCap. Interventions need to be verified in further cohort studies. At present, we are only proposing a theoretical model. Intervention effects need to be validated in further cohort studies.