Pathogenesis of Aeromonas caviae in Clariasmagur

Two novel β-galactosidases from Aeromonas caviae with potential industrial applications in milk and catalytic mechanism analysis using molecular docking

Lactose intolerance has been a significant global health concern, as it is caused by the absence of lactase, leading to the inability of the human body to absorb lactose. This study investigated two genes encoding maltose O-acetyltransferase with β-galactosidase activity from Aeromonas caviae to evaluate their potential application value for lactose degradation in bovine and human milk. The two novel β-galactosidases (AcGal25: 22.0 kDa and AcGal31: 21.3 kDa) were heterologously expressed and biochemically characterized. The optimal pH of both enzymes was 8.0, and the optimal temperature of AcGal25 and AcGal31 were 45 and 42 °C, respectively. Fe2+ and Mn2+ significantly promoted the activity of both enzymes. The two enzymes kept over 75 % activity after incubation for 30 days at 45 °C. HPLC results showed that lactose in bovine milk was completely hydrolyzed by AcGal31 when reacted for 6 h, and about 5 % lactose in human milk was left. The docking results showed that AcGal31 has a more vital lactose-binding ability than AcGal25. LYS129 and ARG165 are highly likely catalytic sites of AcGal31. AcGal31 demonstrated excellent commercial value in making lactose-free milk.

Seasonal and Regional Dynamics of the Intestinal Microbiota in Schizothorax nukiangensis from the Nujiang River

The dynamic alterations in intestinal microbiota can provide insights into the adaptive relationships between these microorganisms and their hosts in response to environmental changes. Schizothorax nukiangensis is widely distributed throughout the Nujiang River and exhibits numerous unique adaptations. In this study, we collected samples of S. nukiangensis across different seasons and regions within the Nujiang River to comprehensively elucidate the diversity and composition of its intestinal microbiota using metagenomic technology. The results indicated that Firmicutes and Proteobacteria predominated at the phylum level, while Priestia, Bacillus, and Aeromonas were the most abundant genera identified. Notably, the relative abundance of these microorganisms varied significantly across different seasons and regions. From autumn through spring and into summer, the predominant microorganisms shifted from Firmicutes to Proteobacteria. Biomarker analysis revealed that Firmicutes (including the class bacilli and the genera Priestia and Bacillus) exhibited a higher relative abundance within the upstream group, where categories related to amino acid metabolism and carbohydrate metabolism were significantly enriched. Conversely, Proteobacteria (including several potential pathogens, such as Saezia, Pantoea, Lelliotia, and Aeromonas genera) showed an increased relative abundance within downstream groups, where disease-related categories exhibited significant enrichment. Our findings significantly enhance our understanding of how S. nukiangensis adapts to its environment, providing valuable data support for the conservation of S. nukiangensis and for ecological security assessment of the Nujiang River.

Characterization of Aeromonas Isolates from Ornamental Fish: Species, Virulence Genes, and Antimicrobial Susceptibility

This study aimed to characterize 300 Aeromonas spp. strains isolated from 123 ornamental fish of 32 different species presenting with septicemia, skin lesions, and/or eye lesions. Within the 300 strains, 53.0% were identified as A. veronii, 41.3% as A. hydrophila, and 5.7% as A. caviae. Among the six virulence genes investigated, the most frequent were act (90.3%) and aer (79.3%). More than 50% of A. hydrophila strains were positive for all the studied genes. A total of 30 virulence profiles were identified, with the five main profiles identified comprising 75% of strains. Only five strains were negative for all genes and were identified as A. caviae and A. veronii. The antimicrobial susceptibility profile was performed for 234 strains, with sulfonamides presenting more than 50% of the resistance rates. Susceptibility was observed mainly for cephalosporins, aminoglycosides, chloramphenicol and piperacillin-tazobactam. Multidrug resistance was detected in 82.5% of the studied strains, including A. caviae with 100% multidrug resistance, and A. hydrophila with 90.9% multidrug resistance. The SE-AFLP analysis resulted in 66 genotypes of A. hydrophila, 118 genotypes of A. veronii, and 14 genotypes of A. caviae, demonstrating the greater heterogeneity of A. veronii and A. caviae. However, no direct correlation was observed between the genotypes and the strains' origins or virulence and resistance profiles.