Effects of decontamination treatment combined with natural chemicals and/or ultra-high pressure on the quality and safety of ready-to-eat wine-pickled mud snails(Bullacta exarata)

Ready-to-eat wine-pickled mud snails(Bullacta exarata)typically host a large number of microorganisms and are frequently contaminated with pathogenic bacteria during processing,resulting in a higher risk for foodborne illness with consumption.In this study,the decontamination effects of different treatment methods,including the use of ultrasonic cleaning(USC),natural chemicals,and ultra-high pressure(UHP),on the quality and safety of pickled mud snails were investigated by assessing the total viable count(TVC),total volatile base nitrogen(TVB-N)content,thiobarbituric acid-reactive substance(TBARS),and pH value of the products after 12 months of storage at-20℃.Treatment with 200 W USC for 5 min was the most effective approach for reducing TVC in raw mud snails,with a minimal change in food quality.Natural chemical treatment or UHP treatment significantly inhibited the increase inTVC,pH,and TBARS and TVB-N accumulation compared with the control group;however,their combined treatment had no synergistic effect.In contrast,the combined chemical treatment was more effective in inhibiting changes in the above indices in pickled mud snails than UHP treatment alone or combined chemicals+UHP treatment.In addition,the bacterial diversity of pickled mud snails before and after 12 months of storage at-20℃was determined using lllumina MiSeq sequencing.Our results indicated that USC combined with natural chemicals can be utilized commercially to maintain the quality and safety of pickled mud snails during storage at-20℃.

Mechanism of actions of Oncocin, a proline- rich antimicrobial peptide, in early elongation revealed by single-molecule FRET

Dear Editor Proline-rich antimicrobial peptides （PrAMPs） are a class of antimicrobial peptides containing a high content of proline residues. PrAMPs selectively target Gram-negative bacteria through special transporters such as SmbA to enter cyto- plasm （Mattiuzzo et al., 2007）. On the other hand, PrAMPs present a low toxicity to mammalian cells, because they cannot effectively penetrate the mammalian cellular mem- brane （Hansen et al., 2012） or they are internalized through an endocytotic process to minimize interaction with cytosolic ribosomes （Tomasinsig et al., 2006）. Therefore, PrAMPs are promising candidates to treat infections and to deliver drugs （Schmidt et al., 2016）.

Single-molecule FRET studies on interactions between elongation factor 4 (LepA) and ribosomes

Elongation factor 4（EF4） is one of the highly conserved translational GTPases, whose functions are largely unknown. Structures of EF4 bound ribosomal PRE-translocation and POST-translocation complexes have both been visualized. On top of cellular, structural, and biochemical studies, several controversial models have been raised to rationalize functions of EF4. However, how EF4 modulates elongation through its interactions with ribosomes has not been revealed. Here, using single-molecule fluorescence resonance energy transfer assays, we directly captured short-lived EF4·GTP bound ribosomal PRE and POST translocation complexes, which may adopt slightly different conformations from structures prepared using GDP, GDPNP, or GDPCP. Furthermore, we revealed that EF4·GTP severely impairs delivery of aminoacyl-tRNA into the A-site of the ribosome and moderately accelerates translocation. We proposed that functions of EF4 are to slow overall elongation and to stall majority of ribosomes in POST states under stress conditions.

Transcriptomics and metabolomics reveal the possible mechanism by which 1-methylcyclopropene regulates the postharvest senescence of Zizania latifolia

To understand the mechanism governing the postharvest senescence of Zizania latifolia(Z.latifolia),and the regulatory mechanism induced by 1-methylcyclopropene(1-MCP)during storage at 25℃,physiobiochemical and conjoint analyses of the transcriptome and metabolome were performed.The results indicated that 1-MCP treatment engendered changes in the expression of genes and metabolites during the postharvest storage of Z.latifolia.The 1-MCP treatment maintained a good visual appearance,preserved the cell structure and membrane integrity of Z.latifolia by keeping the expression of membrane-related lipolytic enzymes(and related genes)low and the amount of phosphatidylethanolamine high.Compared to the control group,1-MCP treatment enhanced the activities of antioxidant enzymes,resulting in a decrease of reactive oxygen species and malondialdehyde contents,and thus inhibition of oxidative damage and loss of membrane integrity.In addition,1-MCP treatment retarded the senescence of Z.latifolia by downregulating the expression of ethylene biosynthesis-related genes and promoting upregulation of brassinosteroid insensitive 1 kinase inhibitor 1,calmodulin,glutathione reductase,jasmonate amino acid synthase,and mitogen-activated protein kinase-related genes.Moreover,1-MCP retarded Z.latifolia senescence by inducing the activity of adenosine triphosphate(ATP)biosynthesis-related genes and metabolites.Our findings should facilitate future research on the postharvest storage of Z.latifolia,and could help delay senescence and prolong the storage time for commercial applications.