Synergistic antibacterial effects of low-intensity ultrasound and peptide LCMHC against Staphylococcus aureus.

The increasing demand for ready-to-eat fresh foods requires the use of non-thermal sterilization, hence, the application of antimicrobial peptides (AMPs) combined with ultrasound could serve as a novel food preservation method to prevent foodborne diseases. In this study, in silico tools were used to predict and screen potential AMPs from the antimicrobial amino acid sequence of myosin heavy chain of Larimichthys crocea. A novel AMP, designated as LCMHC, had strong antibacterial activity against Staphylococcus aureus when combined with low-intensity ultrasound treatment. The minimal inhibitory concentration (MIC) of LCMHC was 125 µg/mL when used alone but 31.25 µg/mL when combined with 0.3 W/cm2 ultrasound treatment. Structural analysis using circular dichroism (CD) revealed that peptide LCMHC has α-helical structure, which had slightly untwisting effect with increasing ultrasonic intensity. Transmission electron microscopy and permeability analysis of bacteria cell membrane showed that low-intensity ultrasound combined with peptide LCMHC could greatly improve the cell membrane permeability of S. aureus. Moreover, low intensity-ultrasound could assist the entry of more peptide LCMHC into bacterial cells to bind DNA. The findings here provide new insight into the potential application of peptide LCMHC combined with low-intensity ultrasound in the food industry.

Low-intensity ultrasound enhances the antimicrobial activity of neutral peptide TGH2 against Escherichia coli.

In recent years, foodborne diseases caused by Escherichia coli are a major threat to the food industry and consumers. Antimicrobial peptides (AMPs) and ultrasound both have good inhibitory effects on E. coli. In this work, the mechanism of action and synergistic effect of an in silico predicted AMP, designated as TGH2 (AEFLREKLGDKCTDRHV), from the C-terminal sequence of Tegillarca granosa hemoglobin, combined with low-intensity ultrasound was explored. The minimal inhibitory concentration (MIC) of TGH2 on E. coli decreased by 4-fold to 31.25 µg/mL under 0.3 W/cm2 ultrasound treatment, while the time kill curve analysis showed that low-intensity ultrasound combined with peptide TGH2 had an enhanced synergistic bactericidal effect after 0.5 h. The permeability on E. coli cell membrane increased progressively during combined treatment with peptide TGH2 and low-intensity ultrasound, resulting in the leakage of intracellular solutes, as shown by transmission electron microscopy (TEM). Structural analysis using circular dichroism (CD) revealed that peptide TGH2 has an α-helical structure, showing a slight untwisting effect under 0.3 W/cm2 ultrasound treatment for 0.5 h. The findings here provide new insight into the potential application of ultrasound and AMPs combination in food preservation.

Antimicrobial mechanism of Larimichthys crocea whey acidic protein-derived peptide (LCWAP) against Staphylococcus aureus and its application in milk.

Antimicrobial peptides are being explored for use as food preservatives to prevent foodborne diseases. In this study, bioinformatics tools were used to screen potential antimicrobial amino acid sequences from the whey acidic protein (WAP) of large yellow croaker (Larimichthys crocea). A novel antimicrobial peptide, designated as LCWAP, was identified and its antimicrobial effect and mechanism of action on Staphylococcus aureus was explored. The minimal inhibitory concentration (MIC) of LCWAP on S. aureus was 15.6 µg/mL. Transmission electron microscopy and laser confocal microscopy revealed that LCWAP kills bacteria by aggregating on the cell surface, destroying the integrity of bacterial cell membrane and resulting in the leakage of intracellular solutes. Moreover, peptide LCWAP inhibit biofilm formation, at concentrations of 1-1/16 × MIC, with biofilm formation found to decrease by 94.3%-13.7% upon LCWAP treatment. The ability of peptide LCWAP to bind bacteria DNA was revealed using electrophoresis analysis and ultraviolet absorption spectroscopy, with peptide LCWAP/DNA weight ratios of 125/1, and 17.3% decrease in the absorption peak of LCWAP. Furthermore, LCWAP had no cytotoxic effects on normal human hepatocytes, although it had strong inhibitory effect on S. aureus growth in milk.

Deep Learning Convolutional Neural Network for the Retrieval of Land Surface Temperature from AMSR2 Data in China.

A convolutional neural network (CNN) algorithm was developed to retrieve the land surface temperature (LST) from Advanced Microwave Scanning Radiometer 2 (AMSR2) data in China. Reference data were selected using the Moderate Resolution Imaging Spectroradiometer (MODIS) LST product to overcome the problem related to the need for synchronous ground observation data. The AMSR2 brightness temperature (TB) data and MODIS surface temperature data were randomly divided into training and test datasets, and a CNN was constructed to simulate passive microwave radiation transmission to invert the surface temperature. The twelve V/H channel combinations (7.3, 10.65, 18.7, 23.8, 36.5, 89 GHz) resulted in the most stable and accurate CNN retrieval model. Vertical polarizations performed better than horizontal polarizations; however, because CNNs rely heavily on large amounts of data, the combination of vertical and horizontal polarizations performed better than a single polarization. The retrievals in different regions indicated that the CNN accuracy was highest over large bare land areas. A comparison of the retrieval results with ground measurement data from meteorological stations yielded R2 = 0.987, RMSE = 2.69 K, and an average relative error of 2.57 K, which indicated that the accuracy of the CNN LST retrieval algorithm was high and the retrieval results can be applied to long-term LST sequence analysis in China.