Acinetobacter Strain KUO11TH, a Unique Organism Related to Acinetobacter pittii and Isolated from the Skin Mucus of Healthy Bighead Catfish and Its Efficacy Against Several Fish Pathogens

Abstract

The bacterial strain KU011TH was isolated from the skin mucus of healthy bighead catfish. The strain is a Gram-negative coccobacillus that is nonmotile, aerobic, catalase positive, oxidase negative, and nonhemolytic. Sequence analyses of the housekeeping genes 16S rRNA, gyrB and rpoB indicate that this strain is a new member of the Acb complex of the genus Acinetobacter and is closely related to Acinetobacter pittii and Acinetobacter lactucae. In addition, the genome relatedness-associated ANIb (<95–96%) and in silico DDH (<70%) values clearly supported the new member of the genus Acinetobacter and the Acb complex. The genome of the strain KU011TH was approximately 3.79 Mbp in size, comprising 3619 predicted genes, and the DNA G+C content was 38.56 mol%. The major cellular fatty acids were C18:1ω9c, C16:0, C16:1, C20:2, C18:2ω6c and C18:1ω9t. The whole-genome sequences and phenotypic, phylogenetic, and chemotaxonomic data clearly support the classification of the strain KU011TH as a new member in the genus Acinetobacter which is closest to A. pittii. Additionally, the new bacterial strain exhibited strong activity against a broad range of freshwater fish pathogens in vitro.

Probiotic Effects of a Novel Strain, Acinetobacter KU011TH, on the Growth Performance, Immune Responses, and Resistance against Aeromonas hydrophila of Bighead Catfish (Clarias macrocephalus Günther, 1864)

“…Acinetobacter KU011TH is a novel probiotic bacterial species in the genus Acinetobacter that was originally isolated from the skin mucus of bighead catfish. From previous research, this strain exhibited high efficacy against several pathogenic bacteria of freshwater fish in vitro, such as A. hydrophila, F. columnare, F. roseus, S. agalactiae, S. warneri and E. tarda [12]. To date, Acinetobacter KU011TH has appreciably enhanced catfish health performance, increasing growth parameters, innate humoral and cellular responses, immune-related gene expression, skin physical defense and disease resistance.…”

“…The Acinetobacter KU011TH bacterium was obtained from the Laboratory of Aquatic Animal Health Management, Department of Aquaculture, Faculty of Fisheries, Kasetsart University, Thailand. This bacterium was entirely described in terms of both genomic and phenotypic information in [12]. The bacterium was routinely grown on plate count agar (PCA, HiMedia Laboratories) at pH 7.3 and incubated at 32 • C for 18-24 h. After incubation, a purified single colony was selected, cultured in a sterilized 50-mL tube in nutrient broth (NB) medium containing 0.5% tryptone, 0.3% yeast extract and 1.0% dextrose/glucose at pH 7.3 and incubated at 32 • C for 18-24 h. Bacterial pellets were obtained by centrifugation at 2500 rpm for 10 min.…”

“…All bacteria-containing tubes were then refrigerated at 4 • C for ten weeks of trials. The shelf life and viable efficacies of the probiotics were measured weekly using bacterial colony counting on PCA plates at 24 h [12]. Additionally, the efficacy of the probiotic against the pathogen A. hydrophila was assessed using an agar dot-spot assay.…”

“…Additionally, the efficacy of the probiotic against the pathogen A. hydrophila was assessed using an agar dot-spot assay. The diameters of clear zones around the probiotic bacteria were measured in centimeters [12]. All tests were performed weekly, with three replications.…”

The Alteration of Intestinal Microbiota Profile and Immune Response in Epinephelus coioides during Pathogen Infection

“…In contrast, the infection group had an increased abundance of pathogenic bacteria. For example, Staphylococcus warneri was generally recognized as a fish pathogen [ 90 ] and is the major cause of infectious diseases in spotted rose snapper [ 91 ] and rainbow trout [ 92 , 93 ]. In MetagenomeSeq analysis, we found Mongoliitalea spp.…”