Summary: The fitness cost of antibiotic resistance is a crucial factor to determine the evolutionary and transmission success of resistant bacteria. Exploring the fitness cost and compensation mechanism of antibiotic resistance genes (ARGs) in bacteria may effectively reduce the transmission of drug‐resistant genes in the environment. Engineered bacteria with the same genetic background that carry sulfonamide resistance gene were generated to explore the fitness cost of sulfonamide resistance gene in Escherichia coli . There were significant differences in the protein expression of the two‐component system pathway ( fliZ , fliA , fliC and lrhA ), folate biosynthesis pathway ( sul1 , sul2 and sul3 ), ABC transporter system ( ugpC , rbsA and gsiA ), and outer membrane pore protein OmpD through the comparative analysis of differential proteins compared to sensitive bacteria. Thus, we could speculate the possible fitness compensation mechanism. Finally, quantitative Real‐time PCR (qRT‐PCR) was used to verify the functions of some differential proteins at the transcriptional level. The fitness cost and compensatory evolution of antibiotic resistance are an essential part of bacterial evolution.

The safety of food additives has been widely concerned. Using single additives in the provisions of scope is safe, but the combination of additives, may induce additive, synergy, antagonism and other joint effects. This study investigated the cytotoxicity of aspartame (AT) together with potassium sorbate (PS). Thiazolyl Blue Tetrazolium Bromide (MTT) assay indicated that AT and PS had IC₅₀ values of 0.48 g/L and 1.25 g/L at 24 h, respectively. High content analysis (HCA) showed that both AT and PS had a negative effect on mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and DNA damage while the joint group behaved more obviously. The biochemical assays revealed typical cell morphological changes and the activation of cytochrome c and caspase-3 verified apoptosis induced by AT together with PS. With dissipation of MMP and increase of cell membrane permeability (CMP), it indicated AT together with PS-induced apoptosis was mediated by mitochondrial pathway. Meanwhile, p53 were involved in DNA damage, and the ratio of Bax/Bcl-2 was increased. Moreover, excessive ROS induced by AT together with PS is a key initiating factor for apoptosis. All these results proved that p53 was involved in apoptosis via mitochondria-mediated pathway and the process was regulated by ROS.

Phages can be used successfully to treat pathogenic bacteria including zoonotic pathogens that colonize the intestines of animals and humans. However, low pH and digestive enzyme activity under harsh gastric conditions affect phage viability, thereby reducing their effectiveness. In this study, alginate (ALG)/κ-carrageenan (CG) microcapsules were developed to encapsulate and release phage under simulated gastrointestinal conditions. The effects of ALG and CG concentrations on the encapsulation and loading efficiency of microcapsules, as well as the release behavior and antibacterial effects of microcapsules in simulating human intestinal pH and temperature, were investigated. Based on various indicators, when the concentration of ALG and CG were 2.0 and 0.3%, respectively, the obtained microcapsules have high encapsulation efficiency, strong protection, and high release efficiency in simulated intestinal fluid. This effect is attributed to the formation of a more tightly packed biopolymer network within the composite microcapsules based on the measurements of their microstructure properties. Bead-encapsulation is a promising, reliable, and cost-effective method for the functional delivery of phage targeting intestinal bacteria.