Xueping Jiang,Hao Li,Jia Kong,Yuqi li,Xiangdong Xin,Jielin Zhou,Ran Zhang,Kwang Sik Lee,Byung Rae Jin,Zhongzheng Gui
Microbial degradation of chloramphenicol (CAP) has become important for reducing the adverse impact of environmental pollution with antibiotics. Although several pathways for CAP degradation have been identified in various bacteria, multiple metabolic pathways and their respective intermediate metabolites within a single strain are rarely reported. Here, Raoultella ornithinolytica CT3 was first isolated from silkworm excrement using CAP as the sole carbon source, and 100 mg/L CAP was almost completely degraded within 48 h. The biodegradation type of CAP followed first-order kinetics. Twenty-two CAP biotransformation products were identified using high-performance liquid chromatography and ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry. The CAP biotransformation pathways were predicted mainly in the acetylation and auxiliary pathways of propionylation and butyrylation. The toxicity of CAP biotransformation products was evaluated using the ecological structure-activity relationship (ECOSAR) model and biological indicators. The results showed that the toxicity of the intermediate metabolites changed slightly, but the final metabolite was harmless to the environment. Genomic analysis predicted that genes encoding acetyltransferase, amido-linkage hydrolase, nitroreductase, haloacetate dehalogenase, and protocatechuate 3,4-dioxygenase were associated with CAP biodegradation. This study provides new insights into the microbial degradation pathway of CAP and constitutes an ecological safety assessment for CAP-contaminated environments.
Bacterial wilt caused by Ralstonia solanacearum severely impacts agricultural production, urgently requiring effective control measures. Herein, we designed a strategy via boron nitride nanosheets with enhanced adhesion ability as nanocarriers to improve the antibacterial efficacy of active ingredients. To achieve this, we utilized three sulfur-containing amino acids (SAAs), including methionine (MET), cysteine (CYS), and cystine (CYST) for the simultaneously exfoliation and functionalization of boron nitride nanosheets (BNNS) through mechanochemical method, and compared their structure–activity relationship. The obtained BNNS-SAAs exhibited size around 160–250 nm and thickness near 1.5–2.0 nm. The presence of disulfide bond (S-S) within BNNS-CYS and BNNS-CYST promoted them with the responsiveness by redox stimuli. BNNS-CYST acquired highest functionalization degree of 63.44 % among three BNNS-SAAs. And tea tree essential oil (TTO) loading capacity within BNNS-SAAs was around 36.40–37.11 %. The existence of SAAs within BNNS significantly inhibited the volatilization of TTO via nanoconfinement effect fitting to Logistic model, specially, BNNS-CYST held with slowest release rate among the BN-based carriers, due to the stronger attachment or affinity. Furthermore, BNNS-CYST-TTO exhibited the most excellent synergistic antibacterial effect with the increased inhibition zone diameter by 26.89 % against Ralstonia solanacearum in comparison with pure TTO, with the minimum inhibition concentration reduced from 1.8 mg·mL −1 to 0.6 mg·mL −1 . The enhanced antibacterial mechanism was proposed based on physical disruption via strong adhesion. BNNS-SAAs also presented superior adhesion and wettability on seed and foliar surfaces, and also promoted seed germination by providing more S nutrients, and exhibited no significant cytotoxicity. Our system provides a green and effective platform response to redox stimuli to load and release essential oils for application in bacterial wilt control.
危险品化学品经营许可证（带存储）