Biocontrol of pseudomonas biofilms in dairy farming environments using bacteriophages

Introduction

Pseudomonads are a genus of ubiquitous Gram-negative bacteria that encompasses species with major impact on food spoilage, especially in the dairy industry. Several physiological properties enable them to persist in production plants and increase the risk of food spoilage: Pseudomonas bacteria are psychrophile and outgrow other bacteria in cool conditions that are often present during storage of fresh produce. Moreover, they form biofilms, allowing them to persist in food plants and efficiently resist sanitation measures. Lastly, a major problem especially in the dairy industry is the ability of some Pseudomonas species to produce heat-stable proteases, which can withstand procedures like ultra-high-temperature treatment of raw milk, causing the decay of milk proteins even after sterilization, and thus leading to premature spoilage of the milk. In order to eliminate Pseudomonas species relevant for milk spoilage, we explore the application of bacteriophages (viruses that infect bacteria) to eradicate persistent biofilms and limit the contamination of milk with heat-stable proteases.

Goals

The goal of this study is to identify potent phages that are active against a broad spectrum of relevant spoilage species like P. proteolytica, P. lactis and P. protegens. The combined use of those phages in a cocktail will be utilized to eradicate Pseudomonas biofilms, which are grown under practically relevant conditions.

Results

A total of 29 phages were isolated. The majority (25) belonged to the Caudoviricetes class, which was expected as it is most prevalent in nature. Within that class, the majority of the isolated phages has not been described in literature. The host range varied significantly and some phages infected as much as 19 host strains, making them interesting candidates for biofilm inhibition. Their efficiency in the eradication of biofilms will be evaluated in coming experiments.

Summary

The use of phages as biocontrol agents against Pseudomonas biofilms is explored in this study and includes the identification of phages infecting relevant bacterial strains and the evaluation of their efficiency to degrade their host"s biofilms.