Partial Characterization of Three Bacteriophages Isolated from Aquaculture Hatchery Water and Their Potential in the Biocontrol of Vibrio spp.

Bacteriophages are currently considered one of the most promising alternatives to antibiotics under the 'One Health' approach due to their ability to effectively combat bacterial infections. This study aimed to characterize Vibrio species in hatchery water samples collected from an aquaculture farm and investigate the biocontrol potential of their bacteriophages. Vibrio spp. (n = 32) isolates confirmed by LNA probe-based qPCR were used as hosts. Three Vibrio phages were isolated. IKEM_vK exhibited a broad host range, infecting V. harveyi (n = 8), V. alginolyticus (n = 2), V. azureus (n = 1), and V. ordalii (n = 1). IKEM_v5 showed lytic activity against V. anguillarum (n = 4) and V. ordalii (n = 1), while IKEM_v14 was specific to V. scophtalmi (n = 4). The morphological appearance of phages and their lytic effects on the host were visualized using scanning electron microscopy (SEM). All three phages remained relatively stable within the pH range of 6-11 and up to 60 °C. The lytic activities and biofilm inhibition capabilities of these phages against planktonic Vibrio cells support their potential applications in controlling vibriosis in aquaculture systems.

Genomic Insights into the Symbiotic and Plant Growth-Promoting Traits of "Candidatus Phyllobacterium onerii" sp. nov. Isolated from Endemic Astragalus flavescens.

A novel strain of Gram-negative, rod-shaped aerobic bacteria, identified as IY22, was isolated from the root nodules of Astragalus flavescens. The analysis of the 16S rDNA and recA (recombinase A) gene sequences indicated that the strain belongs to the genus Phyllobacterium. During the phylogenetic analysis, it was found that strain IY22 is closely related to P. trifolii strain PETP02T and P. bourgognense strain STM 201T. The genome of IY22 was determined to be 6,010,116 base pairs long with a DNA G+C ratio of 56.37 mol%. The average nucleotide identity (ANI) values showed a range from 91.7% to 93.6% when compared to its close relatives. Moreover, IY22 and related strains had digital DNA-DNA hybridization (dDDH) values ranging from 16.9% to 54.70%. Multiple genes (including nodACDSNZ, nifH/frxC, nifUS, fixABCJ, and sufABCDES) associated with symbiotic nitrogen fixation have been detected in strain IY22. Furthermore, this strain features genes that contribute to improving plant growth in various demanding environments. This study reports the first evidence of an association between A. flavescens and a rhizobial species. Native high-altitude legumes are a potential source of new rhizobia, and we believe that they act as a form of insurance for biodiversity against the threats of desertification and drought.

Selection and Molecular Response of AHL-lactonase (aiiA) Producing Bacillus sp. Under Penicillin G-induced Conditions.

Quorum sensing (QS) is the process by which microorganisms employ chemicals called autoinducers (AIs) to communicate with their population. The QS mechanism generally controls the expression of the virulence related genes in bacteria. N-acyl homoserine lactones (AHLs) are the most widespread QS molecules. Due to their diverse AHL-lactonase activities, Bacillus species make particularly suitable candidates for procedures such as demolition of pathogenic bacterial QS signals and bioremediation of ß-lactam antibiotics from contaminated environments. In this study, seven Bacillus strains with Quorum quenching (QQ) activity were isolated using an enrichment medium supplemented with Penicillin G (PenG). The AHL-lactonase encoding gene (aiiA) was amplified by PCR and sequenced. Amino acid sequences underwent multiple sequence alignment. Docking studies were carried out with both C6HSL and PenG ligand using AutoDock tools. The aiiA amino acid sequences of the isolates were found to be well conserved. Furthermore, amino acid sequence alignment revealed that 74.9% of amino acid sequences were conserved in the genus Bacillus. Docking of the C6HSL to wild type (3DHA) and H97D variant reduced the docking score by only 0.1 kcal/mol for the mutated protein. When PenG docked with a higher (1.5 kcal/mol) score as a ligand to wild-type and mutant receptors, the docking score for the mutated protein likewise decreased by 0.1 kcal/mol. This research contributed to the diversification of organisms with QQ activity and beta-lactam antibiotic resistance. It also clarified the binding score of the PenG ligand to the Bacillus AHL lactonase molecule for the first time.