Characterization of a novel melamine-degrading bacterium isolated from a melamine-manufacturing factory in China

Biodegradation of Cyromazine by Mycobacterium sp. M15: Performance, Degradation Pathways, and Key Enzymes

Cyromazine, a triazine insecticide, raises food safety concerns due to residues in vegetables like cowpeas. Microbial metabolism is key for pesticide elimination, but bacteria efficient in cyromazine degradation are limited, with uncharacterized enzymes. This study isolated a highly efficient cyromazine-degrading bacterium, Mycobacterium sp. M15, from a cowpea field. M15 utilized cyromazine as the sole carbon source for its growth and completely degraded 0.5 mM cyromazine within 24 h. The degradation pathway involved hydrolyzing cyromazine to N-cyclopropylammeline and further to N-cyclopropylammelide, with amino groups removed sequentially. The cyclopropylamine group in N-cyclopropionamide continued to hydrolyze to cyanuric acid. A protein, CriA, identified as an aminohydrolase in M15, degraded cyromazine to N-cyclopropylammeline. Using CriA reduced cyromazine residues on cowpea surfaces and completely degraded them in immersion solutions. These findings offer insights into cyromazine's microbial degradation mechanism and highlight the potential of cyromazine-degrading enzymes in enhancing food safety.

Isolation and characterization of cyromazine degrading Acinetobacter sp. ZX01 from a Chinese ginger cultivated soil

Cyromazine, a symmetrical triazine insecticide, is used to control dipteran larvae in chicken manure by feeding to the poultry, flies on animals, and leafminers in vegetables. Its extensive use has resulted in the widespread contamination in the environment. In the current study, a cyromazine degrading bacterium (designated strain ZX01) was isolated and characterized from a Chinese ginger cultivated soil by selective enrichment culture method. On the basis of morphological, biochemical characteristics, and 16S rRNA gene sequence, this bacterium showed strong similarity to the Pseudomonadales members and was closely related to the Acinetobacter baumannii group. Spectrophotometric and HPLC analyses revealed that strain ZX01 degraded cyromazine and utilized it as the sole carbon source for its growth. This process hydrolyzes cyromazine to melamine. Strain ZX01 degraded most of the cyromazine in 60 h. Besides, its substrate specificity against four symmetrical triazine herbicides, one triazinone herbicide, as well as 10 insecticides and its antibiotic sensitivity towards eight commercial antibiotics were also tested. At the concentration of 100 µg/mL for 60 h, it could effectively degrade a variety of different pesticides, including atrazine, prometon, simazine, prometryn, enitrothion, diazinon, cypermethrin, and acetamiprid, and the degradation was in the range of 71-87%. In particular, melamine, the main degradation product of cyromazine, was degraded by 47.3%. This microorganism was sensitive to chloramphenicol and tetracycline and intermediate to amoxicillin and trimethoprim. These results highlight that strain ZX01 can be used as a potential biological agent for the remediation of soil, water, or crop contaminated with cyromazine and other symmetrical triazine insecticides.

Toxicomicrobiomics: The Human Microbiome vs. Pharmaceutical, Dietary, and Environmental Xenobiotics

The harmful impact of xenobiotics on the environment and human health is being more widely recognized; yet, inter- and intraindividual genetic variations among humans modulate the extent of harm, mostly through modulating the outcome of xenobiotic metabolism and detoxification. As the Human Genome Project revealed that host genetic, epigenetic, and regulatory variations could not sufficiently explain the complexity of interindividual variability in xenobiotics metabolism, its sequel, the Human Microbiome Project, is investigating how this variability may be influenced by human-associated microbial communities. Xenobiotic-microbiome relationships are mutual and dynamic. Not only does the human microbiome have a direct metabolizing potential on xenobiotics, but it can also influence the expression of the host metabolizing genes and the activity of host enzymes. On the other hand, xenobiotics may alter the microbiome composition, leading to a state of dysbiosis, which is linked to multiple diseases and adverse health outcomes, including increased toxicity of some xenobiotics. Toxicomicrobiomics studies these mutual influences between the ever-changing microbiome cloud and xenobiotics of various origins, with emphasis on their fate and toxicity, as well the various classes of microbial xenobiotic-modifying enzymes. This review article discusses classic and recent findings in toxicomicrobiomics, with examples of interactions between gut, skin, urogenital, and oral microbiomes with pharmaceutical, food-derived, and environmental xenobiotics. The current state and future prospects of toxicomicrobiomic research are discussed, and the tools and strategies for performing such studies are thoroughly and critically compared.

Chemical transformation of xenobiotics by the human gut microbiota

The human gut microbiota makes key contributions to the metabolism of ingested compounds (xenobiotics), transforming hundreds of dietary components, industrial chemicals, and pharmaceuticals into metabolites with altered activities, toxicities, and lifetimes within the body. The chemistry of gut microbial xenobiotic metabolism is often distinct from that of host enzymes. Despite their important consequences for human biology, the gut microbes, genes, and enzymes involved in xenobiotic metabolism are poorly understood. Linking these microbial transformations to enzymes and elucidating their biological effects is undoubtedly challenging. However, recent studies demonstrate that integrating traditional and emerging technologies can enable progress toward this goal. Ultimately, a molecular understanding of gut microbial xenobiotic metabolism will guide personalized medicine and nutrition, inform toxicology risk assessment, and improve drug discovery and development.

Bacterial biodegradation of melamine-contaminated aged soil: influence of different pre-culture media or addition of activation material

This study aimed to investigate the biodegrading potential of Arthrobacter sp. MCO, Arthrobacter sp. CSP, and Nocardioides sp. ATD6 in melamine-contaminated upland soil (melamine: approx. 10.5 mg/kg dry weight) after 30 days of incubation. The soil sample used in this study had undergone annual treatment of lime nitrogen, which included melamine; it was aged for more than 10 years in field. When R2A broth was used as the pre-culture medium, Arthrobacter sp. MCO could degrade 55 % of melamine after 30 days of incubation, but the other strains could hardly degrade melamine (approximately 25 %). The addition of trimethylglycine (betaine) in soil as an activation material enhanced the degradation rate of melamine by each strain; more than 50 % of melamine was degraded by all strains after 30 days of incubation. In particular, strain MCO could degrade 72 % of melamine. When the strains were pre-cultured in R2A broth containing melamine, the degradation rate of melamine in soil increased remarkably. The highest (72 %) melamine degradation rate was noted when strain MCO was used with betaine addition.

Biodegradation of cyromazine by melamine-degrading bacteria

Biodegradation of cyromazine was investigated in liquid cultures using three melamine-degrading bacteria Arthrobacter sp. MCO, Arthrobacter sp. CSP and Nocardioides sp. ATD6. Experiments were performed aerobically in a mineral medium with glucose as a carbon source and cyromazine as the sole nitrogen source. All three strains of bacteria degraded cyromazine. Cyromazine at 23 mg/L completely disappeared by Arthrobacter sp. MCO within 7 days. The bacterial density of all three strains increased with degradation of the cyromazine. The cyromazine metabolite N-cyclopropylammeline was detected and identified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). This is the first report on the use of Arthrobacter sp. and Nocardioides sp. for cyromazine degradation and the occurrence of bacterial growth with cyromazine degradation.

Degradation of triclocarban by a triclosan-degrading Sphingomonas sp. strain YL-JM2C

Bacterial degradation plays a vital role in determining the environmental fate of micropollutants like triclocarban. The mechanism of triclocarban degradation by pure bacterium is not yet explored. The purpose of this study was to identify metabolic pathway that might be involved in bacterial degradation of triclocarban. Triclosan-degrading Sphingomonas sp. strain YL-JM2C was first found to degrade up to 35% of triclocarban (4 mg L(-1)) within 5 d. Gas chromatography-mass spectrometry detected 3,4-dichloroaniline, 4-chloroaniline and 4-chlorocatechol as the major metabolites of the triclocarban degradation. Furthermore, total organic carbon results confirmed that the intermediates, 3,4-dichloroaniline (4 mg L(-1)) and 4-chloroaniline (4 mg L(-1)) could be degraded up to 77% and 80% by strain YL-JM2C within 5 d.