Characterization of a Lytic Bacteriophage against Pseudomonas syringae pv. actinidiae and Its Endolysin.

Peien Ni,Lei Wang,Bohan Deng,Songtao Jiu,Shiping Wang,Adelaide Almeida,Dapeng Wang,Chao Ma,Caixi Zhang,Wenping Xu

doi:10.3390/v13040631

Abstract

Pseudomonas syringae pv. actinidiae (Psa) is a phytopathogen that causes canker in kiwifruit. Few conventional control methods are effective against this bacterium. Therefore, alternative approaches, such as phage therapy are warranted. In this study, a lytic bacteriophage (PN09) of Psa was isolated from surface water collected from a river in Hangzhou, China in 2019. Morphologically, PN09 was classified into the Myoviridae family, and could lyse all 29 Psa biovar 3 strains. The optimal temperature and pH ranges for PN09 activity were determined as 25 to 35 °C and 6.0 to 9.0, respectively. The complete genome of PN09 was found to be composed of a linear 99,229 bp double-stranded DNA genome with a GC content of 48.16%. The PN09 endolysin (LysPN09) was expressed in vitro and characterized. LysPN09 was predicted to belong to the Muraidase superfamily domain and showed lytic activity against the outer-membrane-permeabilized Psa strains. The lytic activity of LysPN09 was optimal over temperature and pH ranges of 25 to 40 °C and 6.0 to 8.0, respectively. When recombinant endolysin LysPN09 was combined with EDTA, Psa strains were effectively damaged. All these characteristics demonstrate that the phage PN09 and its endolysin, LysPN09, are potential candidates for biocontrol of Psa in the kiwifruit industry.

Highlights

Pseudomonas syringae pv. actinidiae (Psa) is a gram-negative phytopathogen that causes bacterial bleeding canker in kiwifruit [1]
The Psa strains were incubated in a nutrient broth (NB) medium (HuanKai Microbial, Guangdong, China) at 27 ◦ C for 24 h with shaking at 150 rpm, whereas other strains were grown in Luria-Bertani (LB) medium (HuanKai Microbial) at 37 ◦ C with shaking at 150 rpm overnight
The morphological features of PN09 observed using Transmission Electron Microscopy (TEM) indicated that PN09 belongs to the order Caudovirales

Summary

Introduction

Pseudomonas syringae pv. actinidiae (Psa) is a gram-negative phytopathogen that causes bacterial bleeding canker in kiwifruit [1]. Actinidiae (Psa) is a gram-negative phytopathogen that causes bacterial bleeding canker in kiwifruit [1]. The disease is lethal to the kiwifruit plants and causes heavy economic losses [2]. The Psa was first determined from kiwifruit plants in [3]. During the last two decades, the disease has broken out worldwide, including in Korea [4], Italy [5], Portugal [6], France [7], New Zealand [8], and China [9]. Psa has been classified into six biovars (biovars 1–6), according to the secretion of different virulence factors [10]. In recent years, Psa biovar 3 has been the most virulent of the biovars that cause kiwifruit canker [11]

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Discussion

Conclusion