ABSTRACT
Food fermentations depend on the successful growth and development of starter and secondary lactic acid bacteria (LAB). Bacterial viruses, called bacterio (phages), may infect these bacteria and cause slow or failed fermentations. The ecological balance of LAB in natural fermentations may also be affected by the presence of phages that infect specic component cultures. In this chapter, we will examine current knowledge of phage ecology in a variety of food fermentations, the coevolution of phages, and their LAB. Recent advances in genomics have permitted an increased understanding of the variety and evolution of phages infecting LAB and consequently their interactions. Knowledge on
5.1 Introduction .................................................................................................................................... 73 5.2 Food Fermentations and LAB ........................................................................................................ 74 5.3 Phage Ecology and Diversity in Fermented Foods ........................................................................ 74
5.3.1 Fermented Vegetables........................................................................................................ 74 5.3.2 Fermented Meat ................................................................................................................. 75 5.3.3 Fermented Dairy Products ................................................................................................ 75
5.4 Phage Detection Methods and Technological Advances ............................................................... 76 5.5 Phage-Host Interactions ................................................................................................................ 77
5.5.1 Phage-Host Interactions of LAB and Their Phages ......................................................... 77 5.5.2 Prototype Tail-Tip Receptor-Binding Protein of the Siphoviridae ................................... 78 5.5.3 Baseplate-Type Models ...................................................................................................... 78 5.5.4 Overall Baseplate Structure............................................................................................... 79 5.5.5 Identication of the Host Receptor .................................................................................... 80
5.6 Development of Antiphage Strategies ............................................................................................ 81 5.7 Positive Effects of Bacteriophages on Fermented Foods ............................................................... 82
5.7.1 Bacteriophage-Assisted Lysis of the Starter Culture in Flavor Development................... 82 5.7.2 Preservation/Decontamination of Fermented Foods ........................................................ 83 5.7.3 Gram-Positive Spoilage Organisms/Pathogens ................................................................. 83
5.7.3.1 Listeria monocytogenes ..................................................................................... 83 5.7.3.2 Clostridium spp. ................................................................................................. 84 5.7.3.3 Staphylococcus aureus ...................................................................................... 84 5.7.3.4 Bacillus cereus ................................................................................................... 85
5.7.4 Phages as Biocontrol Agents of Gram-Negative Spoilage Organisms/Pathogens ............ 85 5.8 Research toward the Application of Endolysins as Biocontrol Agents.......................................... 85 5.9 Conclusions .................................................................................................................................... 86 Acknowledgments .................................................................................................................................... 86 References ................................................................................................................................................ 86
the interactions of these phages will invariably lead to the development of antiphage strategies that may prevent or reduce the dissemination and development of phages. Additionally, we will discuss the role of structural biology, genetics, proteomics, and glycobiology in dening the receptors for these phages. Numerous host/phage-encoded and engineered phage-resistance systems have been described over the past decades as well as the development of phage-resistant derivatives of starter bacteria. Here, we will discuss the prevalence and potential for application of such resistance systems in LAB in food fermentations. While many food fermentations employ LAB, the presence of LAB may be undesirable in other fermentations, such as those used for beer and wine production. In such situations, the presence of phages that may infect problematic LAB may be benecial to the fermentation. Furthermore, it has been suggested that autolysis and phage-mediated lysis of cultures may be associated with desirable avor production in fermented dairy products, and as such, phages may be benecial to the fermentation and the quality of the end product. The application of phage-encoded lysins in the eradication of pathogenic bacteria in food products has been reported in recent years, supporting the positive role of phages and phage-encoded products in certain food fermentations by improving the safety and preserving the integrity of certain food products.
