作者: Chen, Li ; Shi, Ruili ; Zhang, Hongjun ; Wang, Yanan ; Li, Jian ; Wu, Tonglei ; Zhang, Zhiqiang ; Jia, Qinghui ; Zhao, Bowei ; Wang, Fengjie ; Shi, Qiumei

ABSTRACT:

Escherichia coli K99 is a primary causative agent of diarrhea in young animals, leading to significant health and economic losses. With growing concerns over antibiotic resistance, probiotics—particularly Bacillus species—are gaining attention as effective alternatives for disease prevention and health promotion in livestock. In this study, 39 Bacillus strains were isolated from fresh cattle feces. Preliminary screening focused on biofilm formation, hemolytic activity, and antibacterial effects against E. coli K99. Promising candidates were further evaluated for in vitro probiotic characteristics and safety, including tolerance to acidic and bile salt conditions, heat resistance, hydrophobicity, enzymatic activity, and the presence of virulence and antibiotic resistance genes. In vivo assessments involved acute and subchronic toxicity tests and protective efficacy evaluations in a mouse model challenged with E. coli K99. Four strains—T36, B102, B116, and B150—demonstrated strong biofilm-forming ability, non-hemolytic properties, and notable antimicrobial activity. Among them, B102 and B116 showed excellent probiotic traits and safety profiles in vitro , lacking gelatinase and lecithinase activity, and were free of detectable virulence or resistance genes. In vivo , oral administration of B102 and B116 at high doses caused no acute or subchronic toxicity in mice. Notably, these strains improved the survival rate of E. coli K99-infected mice to 50% and 30%, respectively, compared to 0% in the untreated group. In conclusion, strains B102 and B116 exhibit strong probiotic potential and safety, offering promising alternatives to antibiotics for the prevention and control of E. coli K99 infections in animals. Their application may contribute to sustainable livestock health management.

IMPORTANCE:

Escherichia coli K99-induced diarrhea causes severe economic losses in livestock farming, with limited safe control options due to antibiotic resistance. This study identifies two Bacillus velezensis strains (B102 and B116) that effectively inhibit E. coli K99, enhance survival rates in infected mice, and exhibit strong safety profiles. Their tolerance to gastrointestinal stress and lack of virulence or resistance genes make them ideal antibiotic alternatives. These strains could promote sustainable livestock health by reducing antibiotic use, mitigating resistance risks, and improving disease control, benefiting both agricultural productivity and public health.

Frontiers in plant science

Physiological analysis reveals the mechanism of accelerated growth recovery for rice seedlings by nitrogen application after low temperature stress

Article

作者: Huang, Shiying ; Zhong, Lei ; Fu, Xiaoquan ; Zhao, Desheng ; Chen, Xiaorong ; Wang, Hui ; He, Haohua

Low temperature and overcast rain are harmful to directly seeding early rice, it can hinder rice growth and lower rice biomass during the seedling stage, which in turn lowers rice yield. Farmers usually use N to help rice recuperate after stress and minimize losses. However, the effect of N application on the growth recovery for rice seedlings after such low temperature stress and its associated physiological changes remain unclearly. Two temperature settings and four post-stress N application levels were used in a bucket experiment to compare B116 (strong growth recovery after stress) with B144 (weak growth recovery). The results showed that the stress (average daily temperature at 12°C for 4 days) inhibited the growth of rice seedlings. Compared to the zero N group, the N application group’s seedling height, fresh weight and dry weight significantly increased after 12 days. In particular, the increases in all three growth indicators were relatively higher than that of N application at normal temperature, indicating the importance of N application to rice seedlings after low temperature stress. The antioxidant enzyme activity of rice seedlings increased significantly after N application, which reduced the damaging effect of ROS (reactive oxygen species) to rice seedlings. At the same time, the soluble protein content of seedlings showed a slow decrease, while the H2O2 and MDA (malondialdehyde) content decreased significantly. Nitrogen could also promote nitrogen uptake and utilization by increasing the expression of genes related to NH4+ and NO3− uptake and transport, as well as improving the activity of NR (nitrate reductase) and GS (glutamine synthetase) in rice. N could affect GA3 (gibberellin A3) and ABA (abscisic acid) levels by regulating the anabolism of GA3 and ABA. The N application group maintained high ABA levels as well as low GA3 levels from day 0 to day 6, and high GA3 levels as well as low ABA levels from day 6 to day 12. The two rice varieties showed obvious characteristics of accelerated growth recovery and positive physiological changes by nitrogen application after stress, while B116 generally showed more obvious growth recovery and stronger growth-related physiological reaction than that of B144. The N application of 40 kg hm-2 was more conducive to the rapid recovery of rice growth after stress. The above results indicated that appropriate N application promoted rice seedling growth recovery after low temperature stress mainly by increasing the activities of antioxidant enzymes and nitrogen metabolizing enzymes as well as regulating the levels of GA3 and ABA. The results of this study will provide a reference for the regulation of N on the recovery of rice seedling growth after low temperature and weak light stress.

100 项与 B-116 相关的药物交易

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