Characterization and Genomic Analysis of BUCT549, a Novel Bacteriophage Infecting Vibrio alginolyticus With Flagella as Receptor.

Jing Li,Qiang Pan,Yigang Tong,Wei Lin,Fengjuan Tian,Yujie Liu,Huiying Ren,Yunjia Hu,Feiyang Zhao,Taoxing Shi

doi:10.3389/fmicb.2021.668319

Abstract

Vibrio alginolyticus is one of the most important of pathogens that can infect humans and a variety of aquatic animals, and it can cause food poisoning and septicemia in humans. Widely used antibiotics are gradually losing their usefulness, and phages are gaining more attention as new antibacterial strategies. To have more potential strategies for controlling pathogenic bacteria, we isolated a novel V. alginolyticus phage BUCT549 from seafood market sewage. It was classified as a new member of the family Siphoviridae by transmission electron microscopy and a phylogenetic tree. We propose creating a new genus for BUCT549 based on the intergenomic similarities (maximum is 56%) obtained from VIRIDIC calculations. Phage BUCT549 could be used for phage therapy due to its stability in a wide pH (3.0–11.0) range and high-temperature (up to 60°C) environment. It had a latent period of 30–40 min and a burst size of 141 PFU/infected bacterium. In the phylogenetic tree based on a terminase large subunit, BUCT549 was closely related to eight Vibrio phages with different species of host. Meanwhile, our experiments proved that BUCT549 has the ability to infect a strain of Vibrio parahaemolyticus. A coevolution experiment determined that three strains of tolerant V. alginolyticus evaded phage infestation by mutating the MSHA-related membrane protein expression genes, which caused the loss of flagellum. This research on novel phage identification and the mechanism of infestation will help phages to become an integral part of the strategy for biological control agents.

Highlights

V. alginolyticus is a pathogenic bacterium common in oceans and lakes, and it is prone to causing outbreaks of Vibrio diseases in fish, shrimp, shellfish, and other farmed animals in the aquaculture industry
V. alginolyticus carries resistance genes for doxycycline [tet (35)], tetracycline [tet (34)] and tet [(35)], ampicillin, amoxicillin, and piperacillin, which may be the main reason for the failure to completely kill the bacteria during the culture process, causing diseases among shrimp
BUCT549 grew over a wide pH (3.0– 11.0) and temperature range, which showed it can be used as a potential antibacterial agent in aquatic products or the medical industry

Summary

Introduction

V. alginolyticus is a pathogenic bacterium common in oceans and lakes, and it is prone to causing outbreaks of Vibrio diseases in fish, shrimp, shellfish, and other farmed animals in the aquaculture industry. Ingested V. alginolyticus can cause septicemia and other extra-intestinal infections in humans (Altekruse et al, 2000; Horseman and Surani, 2011; Mohamad et al, 2019). V. alginolyticus has been the third most common Vibrio species in human disease reports for many years (Jacobs Slifka et al, 2017). There has been an upward trend in the incidence of water pollution and food poisoning caused by V. alginolyticus. It worth paying more attention to V. alginolyticus, and it is urgent to develop alternative approaches of antibiotics to control these pathogens (Newton et al, 2012; Osunla and Okoh, 2017)

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