Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2003
Publication Date: 3/20/2003
Citation: Lu, Z., Breidt, F., Fleming, H.P., Altermann, E., Klaenhammer, T.R. 2003. Isolation and characterization of a Lactobacillus plantarum bacteriophage, JL-1, from a cucumber fermentation. International Journal of Food Microbiology. 84:225-235.
Interpretive Summary: This report describes the characterization of a virus (bacteriophage) that infects a bacterium used in vegetable fermentations. This bacterium, Lactobacillus plantarum BI7, has been used as a starter culture in low salt cucumber fermentations and has also been investigated for use as a biocontrol or competitive exclusion agent to ensure the safety of nonfermented fruit and vegetable products. The genome sequence for the virus, which was found to only infect L. plantarum BI7 and a mutant of this culture, MU45, has been determined. The replication kinetics, protein composition, and a variety of other characteristics of the virus have been determined. This is the first report in the scientific literature of a bacterial virus isolated from a cucumber fermentation. Understanding how bacterial viruses affect the growth of the BI7 culture may be important for successful use of this culture in both controlled fermentations and food safety applications.
Technical Abstract: A virulent Lactobacillus plantarum bacteriophage, named PhiJL-1, was isolated from a commercial cucumber fermentation. The phage was specific for two related strains of L. plantarum, BI7 and the derivative mutant MU45, which have been evaluated as starter cultures for controlled cucumber fermentation and as biocontrol microorganisms for minimally processed vegetable products. We report here genome sequencing data for PhiJL-1; the genome size was estimated to be 36.5 kbp. SDS-PAGE profiles indicated that PhiJL-1 contains six structural proteins (28, 34, 45, 50, 61, and 76 kDa). Electron microscopy revealed that the phage has an isometric head (59 nm in diameter), a long non-contractile tail (182 nm in length and 11 nm in width), and a complex base plate. The phage belongs to the Bradley group B or Siphoviridae family. One-step growth kinetics of the phage showed that the latent period was 35 min, the rise period was 40 min, and the average burst size was 22 phage particles per cell. An adsorption experiment (in MRS medium) showed that 90% of phage particles were adsorbed to the host cells 20 min after infection. It was observed that calcium supplementation (up to 30 mM CaCl2) in MRS media did not affect the first cycle of phage adsorption, but greatly promoted rapid phage propagation and cell lysis in the infection cycle subsequent to adsorption. The D values of PhiJL-1 at pH 6.48 were estimated to be 2.7 min at 70C and 0.2 min at 80C by a thermal inactivation experiment. Knowledge of the properties of L. plantarum bacteriophage JL-1 may be important for the development of controlled vegetable fermentations.