Modeling Growth Kinetics of Escherichia coli and Background Microflora in Hydroponically Grown Lettuce.

Hydroponic cultivation of lettuce is an increasingly popular sustainable agricultural technique. However, Escherichia coli, a prevalent bacterium, poses significant concerns for the quality and safety of hydroponically grown lettuce. This study aimed to develop a growth model for E. coli and background microflora in hydroponically grown lettuce. The experiment involved inoculating hydroponically grown lettuce with E. coli and incubated at 4, 10, 15, 25, 30, 36 °C. Growth models for E. coli and background microflora were then developed using Origin 2022 (9.9) and IPMP 2013 software and validated at 5 °C and 20 °C by calculating root mean square errors (RMSEs). The result showed that E. coli was unable to grow at 4 °C and the SGompertz model was determined as the most appropriate primary model. From this primary model, the Ratkowsky square root model and polynomial model were derived as secondary models for E. coli-R168 and background microflora, respectively. These secondary models determined that the minimum temperature (Tmin) required for the growth of E. coli and background microflora in hydroponically grown lettuce was 6.1 °C and 8.7 °C, respectively. Moreover, the RMSE values ranged from 0.11 to 0.24 CFU/g, indicating that the models and their associated kinetic parameters accurately represented the proliferation of E. coli and background microflora in hydroponically grown lettuce.

Population Genetic Analyses and Trichothecene Genotype Profiling of Fusarium pseudograminearum Causing Wheat Crown Rot in Henan, China.

In China, Fusarium pseudograminearum has emerged as a major pathogen causing Fusarium crown rot (FCR) and caused significant losses. Studies on the pathogen's properties, especially its mating type and trichothecene chemotypes, are critical with respect to disease epidemiology and food/feed safety. There are currently few available reports on these issues. This study investigated the species composition, mating type idiomorphs, and trichothecene genotypes of Fusarium spp. causing FCR in Henan, China. A significant shift in F. pseudograminearum-induced FCR was found in the present study. Of the 144 purified strains, 143 were F. pseudograminearum, whereas only 1 Fusarium graminearum was identified. Moreover, a significant trichothecene-producing capability of F. pseudograminearum strains from Henan was observed in this work. Among the 143 F. pseudograminearum strains identified, F. pseudograminearum with a 15ADON genotype was found to be predominant (133 isolates), accounting for 92.36% of all strains, followed by F. pseudograminearum with a 3ADON genotype, whereas only one NIV genotype strain was detected. Overall, a relatively well-balanced 1:1 ratio of the F. pseudograminearum population was found in Henan. To the best of our knowledge, this is the first study that has examined the Fusarium populations responsible for FCR across the Henan wheat-growing region.

Chickpea-Derived Modified Antimicrobial Peptides KTA and KTR Inactivate Staphylococcus aureus via Disrupting Cell Membrane and Interfering with Peptidoglycan Synthesis.

The widespread bacterial contamination caused by foodborne pathogens has continuously driven the development of advanced and potent food antimicrobial agents. In this study, two novel antimicrobial peptides (AMPs) named KTA and KTR were obtained by modifying a natural AMP, Leg2, from chickpea storage protein legumin hydrolysates. They were further predicted to be stable hydrophobic cationic AMPs of α-helical structure with no hemolytic toxicity by several online servers. Moreover, the AMPs exerted superior antibacterial activity against two representative Staphylococcus aureus strains thanks to the increased hydrophobicity and positive charge, with minimum inhibition concentration value (4.74-7.41 µM) significantly lower than that of Leg2 (>1158.70 µM). Further, this study sought to elucidate the specific antimicrobial mechanism against Gram-positive bacteria. It was found that the electrostatic interactions of the AMPs with peptidoglycan were vital for peptide activity in combating Gram-positive bacteria. Subsequently, the cell membrane of S. aureus cells was irreversibly disrupted by increasing permeability and impairing membrane components, which led to the massive release of intracellular substances and eventual cell death. Overall, this work demonstrated that KTA and KTR were active against Gram-positive bacteria via peptidoglycan targeting and membrane-disruptive mechanisms and paved the way for expanding their application potential to alleviate food contamination.