Characterization of SixLeuconostoc fallaxBacteriophages Isolated from an Industrial Sauerkraut Fermentation

Abstract

Six bacteriophages active against Leuconostoc fallax strains were isolated from industrial sauerkraut fermentation brines. These phages were characterized as to host range, morphology, structural proteins, and genome fingerprint. They were exclusively lytic against the species L. fallax and had different host ranges among the strains of this species tested. Morphologically, three of the phages were assigned to the family Siphoviridae, and the three others were assigned to the family Myoviridae. Major capsid proteins detected by electrophoresis were distinct for each of the two morphotypes. Restriction fragment length polymorphism analysis and randomly amplified polymorphic DNA fingerprinting showed that all six phages were genetically distinct. These results revealed for the first time the existence of bacteriophages that are active against L. fallax and confirmed the presence and diversity of bacteriophages in a sauerkraut fermentation. Since a variety of L. fallax strains have been shown to be present in sauerkraut fermentation, bacteriophages active against L. fallax are likely to contribute to the microbial ecology of sauerkraut fermentation and could be responsible for some of the variability observed in this type of fermentation.Industrial sauerkraut fermentation relies on indigenous bacterial populations initially present on raw cabbage (42). Several members of the lactic acid bacterium family are known to contribute to the complex sauerkraut fermentation, including Leuconostoc mesenteroides, Lactobacillus brevis, Pediococcus pentosaceus, and Lactobacillus plantarum (42). Leuconostoc species, including L. mesenteroides and L. fallax, are known to be present and to be predominant in the early heterofermentative stage of this fermentation (7,24,25,36,42).Bacteriophage contamination is an important problem that is common in food fermentations, especially in the dairy industry. Among the bacteriophages that infect lactic acid bacteria, those specific for Streptococcus and Lactococcus species have been investigated most extensively (1). In contrast, little information is available on bacteriophages of Leuconostoc species. It was shown recently that phages active against lactic acid bacteria, including L. mesenteroides, L. plantarum, and P. pentosaceus, are present in pickle and sauerkraut fermentations (6, 57). Leuconostoc phages have also been identified as factors responsible for the failure of fermentations of several foods, including wine, coffee, and dairy products (4,9,18,19,27,28,39,48,49,50).Bacteriophages have the potential to control population levels and microbial diversity in natural bacterial communities (12). The interactions between bacterial and phage populations have been studied in dairy cultures (21), soil environments (17, 41), aquatic environments (8,11,12,29,54), and the phytosphere (5). To understand microbial succession and diversity in the complex sauerkraut fermentation, we must consider the roles and impact of bacteriophages.The primary objective of this work was to investigate the p...

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