Bioaugmentation of Atrazine-Contaminated Soil With Paenarthrobacter sp. Strain AT-5 and Its Effect on the Soil Microbiome.

Atrazine, a triazine herbicide, is widely used around the world. The residue of atrazine due to its application in the fore-rotating crop maize has caused phytotoxicity to the following crop sweet potato in China. Bioaugmentation of atrazine-contaminated soil with atrazine-degrading strains is considered as the most potential method to remove atrazine from soil. Nevertheless, the feasibility of bioaugmentation and its effect on soil microbiome still need investigation. In this study, Paenarthrobacter sp. AT-5, an atrazine-degrading strain, was inoculated into agricultural soils contaminated with atrazine to investigate the bioaugmentation process and the reassembly of the soil microbiome. It was found that 95.9% of 5 mg kg-1 atrazine was removed from the soils when inoculated with strain AT-5 with 7 days, and the phytotoxicity of sweet potato caused by atrazine was significantly alleviated. qRT-PCR analysis revealed that the inoculated strain AT-5 survived well in the soils and maintained a relatively high abundance. The inoculation of strain AT-5 significantly affected the community structure of the soil microbiome, and the abundances of bacteria associated with atrazine degradation were improved.

Taishania pollutisoli gen. nov., sp. nov., Isolated from Tetrabromobisphenol A-Contaminated Soil.

Strain CZZ-1T was isolated from long-term TBBPA-contaminated soil Zaozhuang city, Shandong province, People's Republic of China. CZZ-1T was pink-pigmented, Gram-stain-negative, rod-shaped, non-motile and aerobic. The 16S rRNA gene analysis indicated that strain CZZ-1T shows high similarities to Fluviicola taffensis DSM 16823T (92.6%) and Fluviicola hefeinensis KACC 16597T (92.5%) and less than 91% sequence similarities to other genus or species in the family Crocinitomicaceae. It was able to grow at 10-37 °C, with 0-6% (w/v) NaCl. It could hydrolyze gelatin, but could not reduce nitrates to nitrites. The predominant fatty acids of strain CZZ-1T were iso-C15:0 (51.3%), C15:0 2-OH (11.0%), iso-C17:0 3-OH (8.0%), C14: 0 (7.0%), iso-C15:1 G (6.8%) and Summed Feature 3 (C16:1 ω7c and/or C16:1 ω6c, 4.4%). The polar lipid profile was composed of five unidentified lipids, two unidentified phospholipids, one phosphatidylethanolamine, one unidentified aminolipid and one unidentified glycolipid. The predominant respiratory quinone was MK-6. The genomic DNA G+C content of strain CZZ-1T was 41.5 mol%. Based on data from phenotypic, chemotaxonomic and genotypic analysis in this study, strain CZZ-1T represents a novel species in a new genus in the family Crocinitomicaceae, for which the name Taishania pollutisoli gen. nov., sp. nov. is proposed. The type strain is CZZ-1T (= KCTC 52343T = GDMCC 1.2270T).

A two-component monooxygenase for continuous denitration and dechlorination of chlorinated 4-nitrophenol in Ensifer sp. strain 22-1.

The environmental fates of chlorinated 4-nitrophenols, 2,6-dichloro-4-nitrophenol (2,6-DCNP) and 2-chloro-4-nitrophenol (2C4NP), mediated via microbial catabolism have attracted great attention due to their high toxicity and persistence in the environment. In this study, a strain of Ensifer sp. 22-1 that was capable of degrading both 2,6-DCNP and 2C4NP was isolated from a halogenated aromatic-contaminated soil sample. A gene cluster cnpBADCERM was predicted to be involved in the catabolism of 2,6-DCNP and 2C4NP based on genome sequence analysis. A two-component monooxygenase CnpAB, composed of an oxygenase component (CnpA) and a reductase component (CnpB), was confirmed to catalyze the continuous denitration and dechlorination of 2,6-DCNP and 2C4NP to 6-chlorohydroxyquinol (6-CHQ) and hydroxyquinol (HQ), respectively. Knockout of cnpA resulted in the complete loss of the capacity for strain 22-1 to degrade 2,6-DCNP and 2C4NP. Homologous modeling and docking showed that Val155~Ala159, Phe206~Pro209 and Phe446~Arg461 of CnpA participated in the formation of the FAD-binding pocket, and Arg101, Val155 and Asn447 formed hydrogen bonds with 2,6-DCNP/2C4NP in the substrate-binding pocket. This work characterized a new two-component monooxygenase for 2,6-DCNP and 2C4NP, and enriched our understanding of the degradation mechanism of chlorinated nitrophenols (CNPs) by microorganisms.