ABSTRACT
Aeromonas dhakensis is reported as an emerging pathogenic species within the genus Aeromonas and is widely distributed in tropical coastal areas. This study provided a detailed description and characterization of a strain of A. dhakensis (202108B1) isolated from diseased Ancherythroculter nigrocauda in an inland region of China. Biochemical tests identified the isolate at the genus level, and the further molecular analysis of concatenated housekeeping gene sequences revealed that the strain belonged to the species A. dhakensis. The isolated A. dhakensis strain was resistant to five antibiotics, namely, penicillin, ampicillin, clindamycin, cephalexin and imipenem, while it was susceptible or showed intermediate resistance to most of the other fifteen tested antibiotics. The isolated strain of A. dhakensis caused acute haemorrhagic septicaemia and tissue damage in artificially infected A. nigrocauda, with a median lethal dose of 7.76×104 CFU/fish. The genome size of strain 202108B1 was 5043286 bp, including one chromosome and four plasmids. This is the first detailed report of the occurrence of infection caused by an A. dhakensis strain causing infection in an aquaculture system in inland China, providing important epidemiological data on this potential pathogenic species.
ABSTRACT
Cipangopaludina cathayensis (Gastropoda: Prosobranchia; Mesogastropoda; Viviparidae) is widely distributed in the freshwater habitats of China. It is an economically important snail with high edible and medicinal value. However, the genomic resources and the reference genome of this snail are lacking. In this study, we assembled the first chromosome-level genome of C. cathayensis. The preliminary assembly genome was 1.48 Gb in size, with a contig N50 size of 93.49 Mb. The assembled sequences were anchored to nine pseudochromosomes using Hi-C data. The final genome after Hi-C correction was 1.48 Gb, with a contig N50 of 98.49 Mb and scaffold N50 of 195.21 Mb. The anchored rate of the chromosome was 99.99%. A total of 22,702 protein-coding genes were predicted. Phylogenetic analyses indicated that C. cathayensis diverged with Bellamya purificata approximately 158.10 million years ago. There were 268 expanded and 505 contracted gene families in C. cathayensis when compared with its most recent common ancestor. Five putative genes under positive selection in C. cathayensis were identified (false discovery rate <0.05). These genome data provide a valuable resource for evolutionary studies of the family Viviparidae, and for the genetic improvement of C. cathayensis.
Subject(s)
Genome , Genomics , Animals , Phylogeny , Genome/genetics , Snails/genetics , Chromosomes/geneticsABSTRACT
The area around Poyang Lake is the main aquaculture area in Jiangxi Province, China, and an important base for the supply of freshwater aquatic products. Aquaculture in the Poyang Lake area is severely threatened by diseases caused by bacterial pathogens, and Aeromonas veronii has been the main pathogen in recent years. In this paper, ERIC-PCR genotyping, virulence gene and antimicrobial resistance gene detection, and drug susceptibility tests were carried out on 46 A. veronii isolates obtained from aquaculture systems in the Poyang Lake area from 2016 to 2020. The results showed that the A. veronii strains in the Poyang Lake area had high genetic diversity, and 46 strains produced 36 ERIC genotypes. There were no geographical and temporal differences in the cluster analysis results and no dominant clones. All 13 virulence genes tested were detected, and all isolates had harbored 2 or more virulence genes, with a maximum of 12 virulence genes detected. Among the 22 antimicrobial resistance genes selected, 15 were detected; 97.8% of the isolates contained 2 or more antimicrobial resistance genes, with a maximum of 9 antimicrobial resistance genes. Drug susceptibility tests showed that some strains were resistant to a variety of traditionally effective drugs for Aeromomas, such as enrofloxacin and florfenicol. This study provides a reference for exploring the impact of aquaculture in the Poyang Lake area on public health.
