To investigate the impact of florfenicol on soil microbial community structure and diversity, an indoor florfenicol exposure model was established. Soil samples were collected at different concentrations of florfenicol (0, 0.05, 0.5, 5, and 50 mg/kg) on days 0, 7, 30, and 60. High-throughput sequencing was employed to examine the changes in soil microbial community structure, diversity, and abundance. The analysis revealed a total of 31874 operational taxonomic units ( OTUs ) in the soil samples, averaging 9524 OTUs per sample. The number of soil microbial community OTUs declined with increasing florfenicol concentration. The microbial species richness and diversity showed a decreasing trend at day 7, while the treatment group with 50 mg/kg florfenicol at 60 days exhibited the lowest richness index. Examination of the soil microbial community structure identified 50 phyla and 1303 genera. At the phylum level, the abundance of Actinobacteria and Bacteroides decreased with increasing florfenicol concentration. Similarly, at the genus level, some of the dominant genera displayed a decline in abundance with the rise of florfenicol concentration. Cluster analysis demonstrated significant temporal and concentration variability. The results indicate differences in the composition, diversity, dominance, abundance, and evenness of soil bacterial communities among different groups. Florfenicol has a significant negative impact on the structure and diversity of soil microbial communities. The findings of this study provide a scientific basis for the rational use of florfenicol in livestock farming to maintain a healthy and stable soil microecological environment.

Introduction: The antibacterial protein PAG14 was extracted from a metabolite of Bacillus G14 isolated from mangrove plants.Methods: In this study, Pseudomonas aeruginosa, Pasteurell multocide, Enterobacter aerogenes, and Enterococcus faecalis were used as indicator bacteria to screen endophytes that exhibited antibacterial activity. The endophyte culture conditions were optimized to enhance productivity. Subsequently, the culture supernatant was salted using ammonium sulfate, followed by purification using dextran gel chromatography and ion exchange column techniques. Finally, the structures of antibacterial proteins were identified using mass spectrometry.Results and Discussion: The optimal culture conditions for Bacillus G14 were 2% mannitol, 0.5% fish peptone, 0.05% KH2PO4 + 0.05% K2HPO4 + 0.025% MnSO4·H2O. The antibacterial substances exhibited stability within the temperature range of 30–40°C and pH range of 5.0–7.0, while displaying sensitivity toward enzymes. The antibacterial activity decreased as the duration of UV irradiation increased. The antibacterial protein PAG14, isolated from the culture broth of Bacillus G14 through purification using dextran gel and ion-exchange columns, was identified as a class III bacteriocin using LC-MS/MS, similar to Lysozyme C. These findings serve as a theoretical foundation for the investigation and application of bacteriocins in food products.

To further study saline-alkali soil cultivation, the terminal-restriction fragment length polymorphism (T-RFLP) was used to analyze the effects of different salt concentrations on the denitrification functional genes nirS and nosZ after collecting different soil samples and extracting total soil DNA. The results showed that the variation range of nirS gene abundance was concentrated in 14 segments, the nosZ gene abundance was concentrated in 9 segments. The abundance of nirS gene in paddy soil of different concentrations was higher than nosZ, and the activity of the nirS gene was higher. Diversity index analysis showed that sample I was significantly different from III and V in the Shannon index of the nirS. Sample I and IV were significantly different from III in Simpson index. Except for the significant difference between III and I, II, IV, and V, there was no difference between the other four samples significant in Pielou index. The difference between sampl I and V was extremely significant in Brillouin index. The Shannon index, Simpson index and Pielou index of nosZ gene were not significantly different, sample II and III, IV, V were significantly different in Brillouin index. The diversity of nirS gene was more affected by the salt concentration, and the nirS gene was more widely distributed than nosZ in soil with different salt concentrations. It indicated that nirS-mediated nitrite reductase played an important role in salinity affected soil environment.

为了评价常用抗菌药物对大肠杆菌的体外抑菌效果,采用微量肉汤二倍稀释法测定了红霉素、新霉素、阿莫西林、氟苯尼考、多西环素、替米考星6种抗菌药物对大肠杆菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC)及其联合使用时的抑菌效果.结果表明:大肠杆菌对新霉素、多西环素和阿莫西林3种抗菌药物敏感,对氟苯尼考、红霉素和替米考星均表现为耐受;红霉素与多西环素、替米考星与多西环素、替米考星与新霉素、多西环素与新霉素的联合应用均表现为协同作用;红霉素与氟苯尼考、红霉素与新霉素、替米考星与氟苯尼考、氟苯尼考与新霉素、氟苯尼考与多西环素的联合应用均表现为累加作用;替米考星与红霉素、新霉素与阿莫西林的联合应用均表现为无关作用;阿莫西林与多西环素、阿莫西林与氟苯尼考、阿莫西林与替米考星、阿莫西林与红霉素的联合应用均表现为颉颃作用;红霉素、氟苯尼考、新霉素联合,氟苯尼考、替米考星、新霉素联合均表现为协同作用,其余3种药物组合的抑菌效果则均表现为无关作用.说明不同药物联合应用的抑菌效果不同,还需要不断探索.

By using fumigation extraction and phospholipid fatty acid (PLFA) methods, the change of characteristics of soil microbial community structure caused by residue of colistin sulfate (CS) was studied. The results showed that the CS (w(cs) > or = 5 mg x kg(-1)) had a significant effect on the microbial biomass carbon (MBC) and it was dose-dependent where MBC decreased with the increase of CS concentration in soil. The MBC in soil decreased by 52. 1% when the CS concentration reached 50 mg x kg(-1). The total PLFA of soil in each CS treatment was significantly decreased during the sampling period compared with the control group and showed a dose-dependent relationship. The soil microbial community structure and diversity in the low CS group (w(cs) = 0.5 mg x kg(-1)) were not significantly different from the control group on 7th and 49th day. However, they were significantly different on 21st and 35th day especially in the high CS group (w(cs) = 50 mg x kg(-1)). It was concluded that CS could change the structure of soil microorganisms and varied with time which might be caused by the chemical conversion and degradation of CS in soil.

To evaluate the antibacterial effects of 30 kinds of Chinese herbs and compounds, the minimal inhibitory concentration(MIC) and minimum bactericidal concentration(MBC) of 30 kinds of Chinese herbs against Escherichia coli in vitro, such as Fructus Mume, Galla Chinensis, Fructus Corni, Scutellaria baicalensis Georgi, etc., were measured with test tube double dilution method. Herbal extracts with strong antibacterial effect were screened out and made up Chinese compound to determine their inhibitory effect against E.coli in vitro. The results showed that Galla Chinensis, Fructus Mume, Flos Lonicerae,Folium Isatidis, Scutellaria baicalensis Georgi, Mentha haplocalyx Briq, Fructus Schisandra, Herba Artemisiae Annuae and Ash Bark had significant inhibitory effects against E.coli, especially Galla Chinensis present highest inhibitory effects against E.coli(MIC=6.25 mg/mL), and Fructus Schisandra and Fructus Mume present highest bactericidal effect against E.coli(MBC=50mg/mL). Moreover, the inhibitory effects were improved mostly when the Chinese herbs were combined.