The taxonomic status of a moderately halophilic bacterium, strain N4T, isolated from soil of a chicken farm in China was determined. It was Gram-negative, non-spore-forming, motile, and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequence indicated that this strain belonged to the genus Salinicola, as it showed the highest sequence similarities to Salinicola salaries M27T (98.3 %), Salinicola socius SMB35T (98.1 %), and Salinicola halophilus CG4.1T (98.1 %). The major cellular fatty acids were C16:0 (25.6 %), C18:1ω7c (35.0 %), and C19:0 cyclo ω8c (11.9 %), which are properties shared by members of the genus Salinicola. The DNA G+C content of strain N4T was 69.1 mol %. The level of DNA–DNA relatedness between strain N4T and the other three type strains of the genus of Salinicola salaries M27T, Salinicola socius SMB35T, and Salinicola halophilus CG4.1T were 34.3, 28.7, and 26.9 %, respectively. Based on the results of phenotypic, chemotaxonomic, DNA–DNA relatedness, and phylogenetic analysis, strain N4T should be classified as a novel species of the genus Salinicola, for which the name Salinicola zeshunii sp. nov. is proposed, with strain N4T (=KACC 16602T = CCTCC AB 2012912T) as the type strain.

Rhodococcus sp. strain B1 could degrade 100 mg/L butachlor within 5 days. Butachlor was first hydrolyzed by strain B1 through N-dealkylation, which resulted in the production of butoxymethanol and 2-chloro-N-(2,6-dimethylphenyl)acetamide. Butoxymethanol could be further degraded and utilized as the carbon source for the growth of strain B1, whereas 2-chloro-N-(2,6-dimethylphenyl)acetamide could not be degraded further. The hydrolase designated ChlH, responsible for the N-dealkylation of the side chain of butachlor, was purified 185.1-fold to homogeneity with 16.1% recovery. The optimal pH and temperature of ChlH were observed to be 7.0–7.5 and 30 °C, respectively. This enzyme was also able to catalyze the N-dealkylation of other chloroacetamide herbicides; the catalytic efficiency followed the order alachlor > acetochlor >butachlor > pretilachlor, which indicated that the alkyl chain length influenced the N-dealkylation of the chloroacetamide herbicides. This is the first report on the biodegradation of chloroacetamide herbicides at the enzyme level.

A bacterial strain P2 capable of degrading 3,5,6-trichloro-2-pyridinol (TCP) was isolated and characterized. Phylogenetic analysis based on 16S rRNA gene sequence indicated that it belonged to the genus of Cupriavidus, because it showed the highest sequence similarity to Cupriavidus pauculus LMG 3413T (99.7 %) and DNA–DNA relatedness value between strain P2 and C. pauculus LMG 3413T was 76.8 %. In combination with morphological, physiological and biochemical characters, strain P2 was identified as C. pauculus. It could use TCP as the sole carbon source and energy source for its growth. It showed a high average degradation rate of 10 mg/L h in mineral salt medium amended with TCP (50–800 mg/L). During TCP degradation, chloridion was released into the medium in two obvious discontinuous stages. Along with this, two colorful metabolites were produced. Finally, the molarity of the total released chloridion was three times that of the initial TCP in the medium. This is the first report of TCP-degrading strain from the genus of Cupriavidus and the detection of two colorful metabolites during TCP degradation. Strain P2 might be a promising candidate for its application in the bioremediation of TCP-polluted environments.

•Strain SD-4 was the first MBC-degrading strain isolated from the genus of Mycobacterium.•The codon of mheI was optimized to realize its soluble expression in E.coil.•Key amino acid sites of MheI were identified.A novel carbendazim (methyl-1H-benzimidazol-2-ylcarbamate, or MBC) degrading strain SD-4 was isolated and identified preliminarily as Mycobacterium sp. according to its phenotypic features and phylogenetic analysis. This strain could utilize MBC as the sole carbon and nitrogen sources for growth and degrade 50 mg L−1 MBC at the average degradation rate of 0.63 mg L−1 h−1. Strain SD-4 degraded MBC through the typical pathway, in which MBC was first hydrolyzed by MheI to 2-aminobenzimidazole (2-AB) and then converted to 2-hydroxybenzimidazole (2-HB). The MBC hydrolase encoding gene mheI was cloned from strain SD-4 and successfully expressed in Escherichia coli by codon optimization. The sulfhydryl-blocking assay revealed that the activity of MheI was closely related to cysteine, and the site-directed mutation experiment showed that Cys16 and Cys222 played important roles during the hydrolysis of MBC by MheI. Therefore they affected its activity directly and were defined as the key amino acid sites.