Control of Pseudomonas fluorescens in milk by a novel bacteriophage YZU_PF006

Pseudomonas fluorescens is a psychrophilic bacterium that can cause dairy spoilage through the production of heat-stable enzymes. Bacteriophages are proved as one of the alternatives to control spoilage bacteria in the dairy industry. In this work, a lytic bacteriophage YZU_PF006 against P. fluorescens was isolated from sewage samples in China. Morphology and one-step growth results indicated that this short-tailed phage (a tail length of 5 nm and a head diameter of 58 nm) had a high burst size (180 PFU/infected cells) but a relatively short latent period (60 min). This phage can be inactive after pasteurisation and Clean-In-Place (CIP) procedures. The genomic sequence showed that phage YZU_PF006 had 47 open reading frames (ORFs) but did not have genes for virulence, lysogeny and antibiotic resistance. Phage YZU_PF006 effectively controlled P. fluorescens growth at 7 degrees C and 28 degrees C in milk, which indicates potential for the control P. fluorescens in the dairy industry.