Characterization and genome analysis of six novel Vibrio parahaemolyticus phages associated with acute hepatopancreatic necrosis disease (AHPND).

Vibrio parahaemolyticus causes acute hepatopancreatic necrosis disease (AHPND) in farmed shrimp. Due to its damage potential, which could be as high as a 100% mortality rate, bacteriophages have emerged as a promising natural control intervention other than antibiotics, yet multiple roadblocks need to be overcome. In this study, six bacteriophages isolated from seafood samples, seawater, and estuary water in Sinaloa, Mexico, demonstrated a narrow host range among Mexican AHPND-causing V. parahaemolyticus. All bacteriophages are composed of a double-stranded DNA genome with lengths ranging between 43,268 and 57,805 bp. All six phages exhibited latency periods of 10-30 min and burst sizes of 34-168 viral particles per infected cell. The optimal MOI for bacteriophage propagation was 0.01-1. No transfer RNA (tRNA), virulence, or resistance genes were found in either genome, and the life cycle of these phages was classified as virulent by the PhageAI platform. Phylogenetic and comparative genomics analyzes assigned phages M3, C2, M9, and M83 as new species not yet reported within the genus Maculvirus, Autographiviridae family. ALK and CHI phages were assigned as new members of a new genus not yet classified within the subfamily Queuovirinae. The findings highlight the potential of CHI, ALK, M3, C2, M9, and M83 as promising alternatives against AHPND-causing V. parahaemolyticus from Mexico.

Genomic Characterization of Twelve Lytic Bacteriophages Infecting Midgut Bacteria of Aedes aegypti.

Mosquito-borne diseases such as malaria and dengue are global severe public health threats. Due to the lack of efficient control methods, alternative approaches to decreasing arboviral transmitted diseases are prioritized to reduce morbidity and mortality in every endemic region. Mosquito midgut bacteria play an essential role in physiological development, fitness, and the arthropods´ vectorial capacity. Bacteriophages are viruses that infect bacteria and are considered a promising biocontrol method by eliminating midgut microbiota that plays an essential role in mosquitoes´ health. Here, we isolate and identify 22 bacteria from mosquito´s midgut belonging to the genera Mesobacillus, Enterobacter, Klebsiella, Microbacterium, Micrococcus, Pantoea, Serratia, and Staphylococcus, mainly. Twelve phages with lytic activity against Enterobacter, Klebsiella, and Pantoea were also isolated. All 12 phages showed a double-stranded DNA genome, ranging from 36,790 to 149,913 bp, and were taxonomically classified as members of the Drexlerviridae family, Molineuxvirinae, Studiervirinae, and Vequintavirinae subfamilies. Open reading frames associated with phage structure, packing, host lysis, DNA metabolism, and additional functions were predicted in all 12 phage genomes, while tRNAs were predicted in five phage genomes. In addition, the life cycle was predicted as virulent for the 12 phages, and no antibiotic resistance, virulence, allergenic, or lysogenic genes were found in either genome. These findings suggest that the 12 phages have biocontrol potentials; however, it is necessary to elucidate specific bacterial host's roles and then the phages' ability to serve as effective vector control.

Genomic and biological characterization of the novel phages vB_VpaP_AL-1 and vB_VpaS_AL-2 infecting Vibrio parahaemolyticus associated with acute hepatopancreatic necrosis disease (AHPND).

Acute hepatopancreatic necrosis disease (AHPND) is a life-threatening disease to recently stocked shrimp. This disease is mainly caused by Vibrio parahaemolyticus and, to date, it has not been effectively controlled. Bacteriophages are a promising method to control bacterial diseases in aquaculture and multiple phages that infect Asian strains of V. parahaemolyticus have been described. However, few studies have characterized the bacteriophages that infect Latin American strains. Here, two lytic Vibrio phages (vB_VpaP_AL-1 and vB_VpaS_AL-2) were isolated from estuary water in Sinaloa, Mexico. The host ranges were tested using ten AHPND-causing strains isolated from Mexico and phage AL-1 was able to infect two strains while AL-2 infected four. One-step growth curve showed that AL-1 produced 85 PFU/cell and AL-2 produced 68 PFU/cell in 30 and 40 min, respectively. Both phages were able to tolerate temperatures ranging from 20 to 50 °C and pH values ranging from 4 to 10. Phages AL-1 and AL-2 have double-stranded DNA genomes of 42,854 bp and 58,457 bp, respectively. In total, 53 putative ORFs associated with the phage structure, packing, host lysis, DNA metabolism, and additional functions were predicted in the AL-1 genome, while 92 ORFs associated with the same functions as the AL-1 and 1 tRNA were predicted in the AL-2 genome. The lifecycle was classified as virulent for both phages. Morphology, phylogeny, and comparative genomic analyses assigned phage AL-1 as a new member of the genus Maculvirus in the Autographiviridae family, and phage AL-2 as a new member of the Siphoviridae family. These findings suggest that vB_VpaP_AL-1 and vB_VpaS_AL-2 are potential biocontrol agents against AHPND-causing V. parahaemolyticus from Mexico.

Metabolic plasticity of Salmonella enterica as adaptation strategy in river water.

The survival of Salmonella in subtropical river water depends on genetic and metabolic reorganization for the expression of alternative metabolic pathways in response to starvation, which allows Salmonella to use environmental carbon sources (C-sources). However, knowledge regarding the metabolic plasticity of Salmonella serotypes for C-source utilization when exposed to these conditions remains unclear. The aim of this study was to evaluate the metabolic response and level of environmental C-source consumption by environmental Salmonella (Oranienburg and Saintpaul) and clinical Salmonella (Typhi) serotypes by comparing laboratory growth against exposure to river water conditions. Metabolic characterization was performed using a Biolog® EcoPlateTM containing 31 C-sources. The results obtained under laboratory growth conditions showed that environmental serotypes used 74.1% of the C-sources, whereas the clinical serotype used 45.1%. In contrast, in river water, all strains used up to 96.7% of the C-sources. Salmonella exposure to river water increases its capacity to use environmental C-sources.