Degradation of Atrazine by an Anaerobic Microbial Consortium Enriched from Soil of an Herbicide-Manufacturing Plant.

Atrazine is an important herbicide that has been widely used for weed control in recent decades. However, with the extensive use of atrazine, its residue seriously pollutes the environment. Therefore, the microbial degradation and detoxification of atrazine have received extensive attention. To date, the aerobic degradation pathway of atrazine has been well studied; however, little is known about its anaerobic degradation in the environment. In this study, an anaerobic microbial consortium capable of efficiently degrading atrazine was enriched from soil collected from an herbicide-manufacturing plant. Six metabolites including hydroxyatrazine, deethylatrazine, N-isopropylammelide, deisopropylatrazine, cyanuric acid, and the novel metabolite 4-ethylamino-6-isopropylamino-1,3,5-triazine (EIPAT) were identified, and two putative anaerobic degradation pathways of atrazine were proposed: a hydrolytic dechlorination pathway is similar to that seen in aerobic degradation, and a novel pathway initiated by reductive dechlorination. During enrichment, Denitratisoma, Thiobacillus, Rhodocyclaceae_unclassified, Azospirillum, and Anaerolinea abundances significantly increased, dominating the enriched consortium, indicating that they may be involved in atrazine degradation. These findings provide valuable evidence for elucidating the anaerobic catabolism of atrazine and facilitating anaerobic remediation of residual atrazine pollution.

Crystal structures of herbicide-detoxifying esterase reveal a lid loop affecting substrate binding and activity.

SulE, an esterase, which detoxifies a variety of sulfonylurea herbicides through de-esterification, provides an attractive approach to remove environmental sulfonylurea herbicides and develop herbicide-tolerant crops. Here, we determined the crystal structures of SulE and an activity improved mutant P44R. Structural analysis revealed that SulE is a dimer with spacious binding pocket accommodating the large sulfonylureas substrate. Particularly, SulE contains a protruding ß hairpin with a lid loop covering the active site of the other subunit of the dimer. The lid loop participates in substrate recognition and binding. P44R mutation altered the lid loop flexibility, resulting in the sulfonylurea heterocyclic ring repositioning to a relative stable conformation thus leading to dramatically increased activity. Our work provides important insights into the molecular mechanism of SulE, and establish a solid foundation for further improving the enzyme activity to various sulfonylurea herbicides through rational design.

Anaerobic biodegradation and detoxification of chloroacetamide herbicides by a novel Proteiniclasticum sediminis BAD-10T.

Chloroacetamide herbicides (CAAHs) are important herbicides that were widely used to control agricultural weeds. However, their mass applications have seriously contaminated environment, and they are toxic to living beings. CAAHs are easy to enter anoxic environments such as subsoil, wetland sediment, and groundwater, where CAAHs are mainly degraded by anaerobic organisms. To date, there are no research on the anaerobic degradation of CAAHs by pure isolate and toxicity of anaerobic metabolites of CAAHs. In this study, the anaerobic degradation kinetics and metabolites of CAAHs by an anaerobic isolate BAD-10T and the toxicity of anaerobic metabolites were studied. Isolate BAD-10T could degrade alachlor, acetochlor, propisochlor, butachlor, pretilachlor and metolachlor with the degradation kinetics fitting the pseudo-first-order kinetics equation. The degradation rates of CAAHs were significantly affected by the length of N-alkoxyalkyl groups, the shorter the N-alkoxyalkyl groups, the higher the degradation rates. Four metabolites 2-ethyl-6-methyl-N-(ethoxymethyl)-acetanilide (EMEMA), N-(2-methyl-6-ethylphenyl)-acetamide (MEPA), N-2-ethylphenyl acetamide and 2-ethyl-N-carboxyl aniline were identified during acetochlor degradation, and an anaerobic catabolic pathway of acetochlor was proposed. The toxicity of EMEMA and EMPA for zebrafish, Arabidopsis and Chlorella ellipsoidea were obviously lower than that of acetochlor, indicating that the anaerobic degradation of acetochlor by isolate BAD-10T is a detoxification process. The work reveals the anaerobic degradation kinetics and catabolic pathway of CAAHs and highlights a potential application of Proteiniclasticum sediminis BAD-10T for bioremediation of CAAHs residue-contaminated environment.

Sinanaerobacter chloroacetimidivorans gen. nov., sp. nov., an obligate anaerobic bacterium isolated from anaerobic sludge.

An obligate anaerobic bacterial strain (BAD-6T) capable of degrading acetochlor and butachlor was isolated from an anaerobic acetochlor-degrading reactor. Cells were Gram-stain positive, straight to gently curved rods with flagella. The major fermentation products in peptone-yeast broth were acetate and butyrate. The optimum temperature and pH for growth was 30 °C and 7.2-7.5, respectively. The major cellular fatty acids (> 10%) were C14:0 FAME, C16:0 FAME and cyc-9,10-C19:0 DMA. Genome sequencing revealed a genome size of 4.80 Mb, a G + C content of 43.6 mol% and 4741 protein-coding genes. The most closely related described species on the basis of 16S rRNA gene sequences was Anaerovorax odorimutans NorPutT in the order Clostridiales of the class Clostridia with sequence similarity of 94.9%. The nucleotide identity (ANI) value and digital DNA-DNA hybridization (dDDH) between the genomes of strain BAD-6T and Ana. odorimutans NorPutT were 70.9% and 15.9%, respectively. Based on the distinct differences in phylogenetic and phenotypic characteristics between strain BAD-6T and related species, Sinanaerobacter chloroacetimidivorans gen. nov., sp. nov. is proposed to accommodate the strain. Strain BAD-6T is the type strain (= CCTCC AB 2021092T = KCTC 25290T).

Rhodobacter kunshanensis sp. nov., a Novel Bacterium Isolated from Activated Sludge.

Strain HX-7-19T was isolated from the activated sludge collected from an abandoned herbicide manufacturing plant in Kunshan, China. Cells were Gram-reaction-negative, rod-shaped, and non-motile. The phylogenetic analysis based on 16S rRNA gene indicated that strain HX-7-19T formed a clade with Rhodobacter blasticus CGMCC 1.3365T (96.3% sequence similarity). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain HX-7-19T and R. blasticus CGMCC 1.3365T were 76.2% and 20.3%, respectively. The genomic DNA G + C content of strain HX-7-19T was 65.9%. The major fatty acids (> 10% of the total fatty acids) were C18:1 ω7c and C18:1 ω7c 11-methyl. The major respiratory quinone was quinone Q-10. The major polar lipid profile consists of phosphatidylglycerol (PG), diphosphatidyl-glycerol (DPG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC). Photosynthesis pigments bacteriochlorophyll a and carotenoids were formed and photosynthesis genes pufL and pufM were detected. On the basis of phenotypic and phylogenetic evidences, strain HX-7-19T is considered as a novel species in the genus Rhodobacter, for which the name Rhodobacter kunshanensis sp. nov. is proposed. The type strain is HX-7-19T (= KCTC 72471T = CCTCC AB 2020148T).

Proteiniclasticum sediminis sp. nov., an obligate anaerobic bacterium isolated from anaerobic sludge.

An obligate anaerobic bacterial BAD-10 T was isolated from anaerobic acetochlor-degrading sludge. The strain was Gram-stain negative, curved rod-shaped, non-motile and non-spore-forming. Growth was observed in PYT medium at pH 6.0-9.0 (optimum, pH 7.5), at 25-47 °C (37 °C) and with 0-1.0% NaCl (w/v, 0%). Strain BAD-10 T could degrade acetochlor. The major fermentation products from peptone-yeast (PY) medium were acetate and butyrate. The predominant cellular fatty acids were iso-C15:0 FAME, anteiso-C15:0 FAME and C16:0 FAME. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain BAD-10 T showed closest affiliation to Proteiniclasticum ruminis D3RC-2 T, with a sequence similarity of 97.6%. Genome sequencing revealed a genome size of 2,983,986 bp, a G + C content of 51.4 mol% and protein-coding genes of 3,102. The average nucleotide identity and in silico DNA-DNA hybridization values between strain BAD-10 T and Proteiniclasticum ruminis D3RC-2 T were 71.0% and 20.4%, respectively, which were below the standard thresholds for species differentiation. On the basis of phenotypic, physiological and phylogenetic evidence, strain BAD-10 T represents a novel species in the genus Proteiniclasticum, for which the name Proteiniclasticum sediminis sp. nov. is proposed. Strain BAD-10 T (= CCTCC AB 2021091 T = KCTC 25288 T) is the type strain of the proposed novel species.

Kitamycin C, a new antimycin-type antibiotic from Streptomyces antibioticus strain 200-09.

An actinomycete strain 200-09, isolated from a soil sample collected from the coast of Hawaii, USA, was identified as Streptomyces antibioticus on the basis of its morphological, physiological and biochemical characteristics as well as 16S rDNA analysis. A new antimycin-type antibiotic, kitamycin C (1), together with kitamycin A (2), kitamycin B (3), urauchmycin B (4), deisovaleryblastomycin (5) was isolated from a cultured broth of strain 200-09. The structure of the new compound was determined by spectroscopic data, including HR-ESI-MS and NMR. All the compounds exhibited antifungal activities against Candida albicans with MIC of about 25.0 µg mL-1.

Secondary metabolites from marine-derived Streptomyces antibioticus strain H74-21.

A new secondary metabolite, (2S,3R)-l-threonine, N-[3-(formylamino)-2-hydroxybenzoyl]-ethyl ester (streptomyceamide C, 1), together with four known compounds 1, 4-dimethyl-3-isopropyl-2,5-piperidinedione (2), cyclo-((S)-Pro-8- hydroxy-(R)-Ile (3), cyclo-((S)-Pro-(R)-Leu (4), and seco-((S)-Pro-(R)-Val) (5), were isolated from the EtOH extract of the fermented mycelium of the marine-derived streptomycete strain H74-21, which was isolated from sea sediment in a mangrove site. The structure of the new compound was established on the basis of its spectroscopic data, including 1D and 2D NMR, HR-TOF-MS. Their antifungal activities against Candida albicans and cytotoxicities against human breast adenocarcinoma cell line MCF-7, human glioblastoma cell line SF-268 and human lung cancer cell line NCI-H460 were tested. Compounds 1 only displayed cytotoxicity against human breast adenocarcinoma cell line MCF-7 with the IC50 value of 27.0 µg/mL. However, compounds 1-5 do not show antifungal activities at the test concentration of 1 mg/mL, and 2-5 have no cytotoxicities at the test concentration of 50 µg/mL.