Project description:Antibiotic resistance (AMR) in aquatic bacteria affecting aquaculture has been a growing concern given the potential for mixing of bacterial populations in the aquatic environment and exposure to different pharmaceuticals from drugs used in aquaculture, as well as wastewater effluent and agricultural run-off. To better understand the mechanism for AMR in a common aquatic fish pathogen exposed to low dose antibiotics we monitored the genetic changes, as well as gene expression, in Aeromonas hydrophila as the bacteria was exposed to incremental doses of oxytetracycline (OTC), a commonly used drug in aquaculture. We were able to render all three isolates of our original A. hydrophila resistant to therapeutic levels of OTC (i.e. ≥100ppm). The relatively quick phenotypic adaptation (often less than 3 days) to different OTC concentrations was very similar across our replicates. Our whole genome sequencing data and transcriptome results suggested several genes underwent point mutations across all replicates. Further differential gene expression was observed and likely impacted several pathways which may explain the progressive resistance to OTC associated with incremental exposure to the drug. The specific mutations consistently identified in isolates exposed to OTC were on AHA_ 2785 (associated with an outer membrane protein), AHA_2910 (involved in the efflux pump mechanism), and AHA_0308 (associated with the small ribosomal subunit protein S10). The pathways involved in the differential gene expression included efflux- pump mechanisms, outer membrane proteins, and ribosomal protein OTC target. Our findings support the notion that AMR can occur via genetic regulation of several intrinsic mechanisms within a bacterial population. This finding could have implications in aquaculture where bacteria such as A. hydrophila can be exposed to varying levels of antibiotics during in-feed treatments.
Project description:Aeromonas hydrophila is one of the most important pathogenic bacteria for aquaculture animals, such as fish and crustaceans. In this study, we isolated a pathogenic bacterial strain, named Y-SC01, from dark sleeper (Odontobutis potamophila) with rotten gills; the strain was identified as A. hydrophila by physiological and biochemical tests. Furthermore, we sequenced its genome and assembled a chromosome of 4.72 Mb with a GC content of 58.55%, and we report major findings based on the genomic analysis.
Project description:The mucosal surfaces of fish serve as the first-line of defense against the myriad of aquatic pathogens present in the aquatic environment. The immune repertoire functioning at these interfaces is still poorly understood. The skin, in particular, must process signals from several fronts, sensing and integrating environmental, nutritional, social, and health cues. Pathogen invasion can disrupt this delicate homeostasis with profound impacts on signaling throughout the organism. Here, we investigated the transcriptional effects of virulent A. hydrophila infection in channel catfish skin, Ictalurus punctatus. We utilized an 8X60K Agilent microarray to examine gene expression profiles at critical early timepoints following challenge—2 h, 8 h, and 12 h. Expression of a total of 2,168 unique genes was significantly perturbed during at least one timepoint. We observed dysregulation of a number of genes involved in antioxidant, cytoskeletal, immune, junctional, and nervous system pathways. In particular, A. hydrophila infection rapidly altered a number potentially critical lectins, chemokines, interleukins, and other mucosal factors in a manner predicted to enhance its ability to adhere and invade the catfish host.
Project description:The bacterium Aeromonas veronii is a co-pathogenic species that can negatively impact the health of both humans and aquatic animals. In this study, we used single-cell transcriptome analysis (scRNA-seq) to investigate the effects of infection with A. veronii on head kidney cells and the regulation of gene expression in the dark sleeper (Odontobutis potamophila). scRNA-seq was used to assess the effects of infection with A. veronii in O. potamophila B cells, endothelial cells, macrophages, and granulocytes, and differential enrichment analysis of gene expression in B cells and granulocytes was performed. The analyses revealed a significant increase in neutrophils and decrease in eosinophils in granulocytes infected with A. veronii. Activation of neutrophils enhanced ribosome biogenesis by up-regulating the expression of rps12 and rpl12 to fight against invading pathogens. Crucial pro-inflammatory mediators il1b, ighv1-4, and the major histocompatibility class II genes mhc2a and mhc2dab, which are involved in virulence processes, were up-regulated, suggesting that A. veronii activates an immune response that presents antigens and activates immunoglobulin receptors in B cells. These cellular immune responses triggered by infection with A. veronii enriched the available scRNA-seq data for teleosts, and these results are important for understanding the evolution of cellular immune defense and functional differentiation of head kidney cells.
Project description:Fish skin is a critical regulatory organ, serving not only as a physical barrier to pathogen entry, but also as a sophisticated integrator of aquatic environmental, social and nutritional cues through roles in immunity, osmoregulation, and endocrine signaling. Integral to the complexity of teleost skin is the mucus layer secreted by epidermal goblet cells. Pathogen invasion can disrupt this delicate homeostasis with profound impacts on signaling throughout the organism. Here, we investigated the transcriptional effects of virulent A. hydrophila infection in blue catfish skin, Ictalurus furcatus. We utilized an 8X60K Agilent microarray to examine gene expression profiles at critical early timepoints following challenge—2 h, 12 h, and 24 h. Expression of a total of 1,155 unique genes was significantly perturbed during at least one timepoint. We observed dysregulation of a number of genes involved in including antioxidant/apoptosis, cytoskeletal rearrangement, immune response, junctional/adhesion, and proteases. In particular, A. hydrophila infection rapidly altered a number potentially critical lectins, chemokines, interleukins, and other mucosal factors in a manner predicted to enhance its ability to adhere and invade the catfish host.
Project description:We report the first complete mitochondrial genome of Odontobutis obscurus, which consists of 17,038 bp harboring 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a control region (D-loop). The overall base composition of the complete genome is A (30.63%), C (28.72%), T (25.70%), G (14.95%). The complete mitogenome of Odontobutis obscurus, most closely related to congeners in the Bayesian inference and maximum likelihood tree, provides a better understanding of the phylogeny of the genus Odontobutis.
Project description:Fish skin is a critical regulatory organ, serving not only as a physical barrier to pathogen entry, but also as a sophisticated integrator of aquatic environmental, social and nutritional cues through roles in immunity, osmoregulation, and endocrine signaling. Integral to the complexity of teleost skin is the mucus layer secreted by epidermal goblet cells. Pathogen invasion can disrupt this delicate homeostasis with profound impacts on signaling throughout the organism. Here, we investigated the transcriptional effects of virulent A. hydrophila infection in blue catfish skin, Ictalurus furcatus. We utilized an 8X60K Agilent microarray to examine gene expression profiles at critical early timepoints following challenge—2 h, 12 h, and 24 h. Expression of a total of 1,155 unique genes was significantly perturbed during at least one timepoint. We observed dysregulation of a number of genes involved in including antioxidant/apoptosis, cytoskeletal rearrangement, immune response, junctional/adhesion, and proteases. In particular, A. hydrophila infection rapidly altered a number potentially critical lectins, chemokines, interleukins, and other mucosal factors in a manner predicted to enhance its ability to adhere and invade the catfish host. Two-condition experiment, control vs. infected skin. Biological replicates: 3 control replicates, 3 infected replicates.3 timepoints