Rise and metabolic roles of Vibrio during the fermentation of crab paste.

Microbial community may systematically promote the development of fermentation process of foods. Traditional fermentation is a spontaneous natural process that determines a unique nutritional characteristic of crab paste of Portunus trituberculatus, However, rare information is available regarding the development pattern and metabolic role of bacterial community during the fermentation of crab paste. Here, using a 16S rRNA gene amplicon sequencing technology, we investigated dynamics of bacterial community and its relationship with metabolites during the fermentation of crab paste. The results showed that bacterial community changed dynamically with the fermentation of crab paste which highlighted by consistently decreased α-diversity and overwhelming dominance of Vibrio at the later days of fermentation. Vibrio had a positive correlation with trimethylamine, hypoxanthine, formate, and alanine while a negative correlation with inosine and adenosine diphosphate. In contrast, most of other bacterial indicators had a reverse correlation with these metabolites. Moreover, Vibrio presented an improved function potential in the formation of the significantly increased metabolites. These findings demonstrate that the inexorable rise of Vibrio not only drives the indicator OTUs turnover in the bacterial community but also has incriminated the quality of crab paste from fresh to perished.

The Functions of Pt-DIC and Pt-Lamin B in Spermatogenesis of Portunus trituberculatus.

Cytoplasmic Dynein is a multiple-subunit macromolecular motor protein involved in the transport process of cells. The Dynein intermediate chain (DIC) is one of the subunits of Dynein-1. In our previous studies, we showed that Pt-DIC may play an important role in the nuclear deformation of spermiogenesis in Portunus trituberculatus. Lamin B is essential for maintaining nuclear structure and functions. Surprisingly, Pt-Lamin B was expressed not only in the perinucleus but also in the pro-acrosome during spermiogenesis in P. trituberculatus. Studies have also shown that Dynein-1 can mediate the transport of Lamin B in mammals. Thus, to study the relationship of Pt-DIC and Pt-Lamin B in the spermatogenesis of P. trituberculatus, we knocked down the Pt-DIC gene in P. trituberculatus by RNAi. The results showed that the distribution of Pt-DIC and Pt-Lamin B in spermiogenesis was abnormal, and the colocalization was weakened. Moreover, we verified the interaction of Pt-DIC and Pt-Lamin B via coimmunoprecipitation. Therefore, our results suggested that both Pt-DIC and Pt-Lamin B were involved in the spermatogenesis of P. trituberculatus, and one of the functions of Dynein-1 is to mediate the transport of Lamin B in the spermiogenesis of P. trituberculatus.

ATP catabolism and bacterial succession in postmortem tissues of mud crab (Scylla paramamosain) and their roles in freshness.

The seafood microbiome is highly diverse and plays an essential role in the spoilage of seafood. Nevertheless, how such a diverse microbiome influences freshness of mud crab (Scylla paramamosain) remains unclear. Here we investigated the postmortem ATP catabolism and succession of the bacterial community in the hepatopancreas and muscle of S. paramamosain using a high-performance liquid chromatography method and 16S rRNA gene amplicon sequencing. Our results showed a tissue-dependent change in ATP catabolism determinized the differences in the changes of nucleotide freshness indices of hepatopancreas and muscle over postmortem time of mud crab. The muscle K value could be used as an optimal nucleotide freshness indicator for the freshness of mud crab, with a proposed threshold of 20%. From a microbiota perspective, a more significant bacterial community change was observed in the muscle than in the hepatopancreas. These changes could result in a close relationship between ATP and its catabolites and microbial taxa in the muscle. Moreover, Photobacterium, Peptostreptococcaceae, average path distance, OTU richness, and Shannon index of muscle bacterial community markedly contributed to K value. These findings suggest that the mud crab of 4 h postmortem at room temperature is still edible. Notably, the importance of microbial community composition and interaction for the spoilage of mud crab should be carefully considered.