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Producing food efficiently is a global issue. Ultimately, lack of food at a global level, results in millions going hungry every year. One reason for this, is that a large proportion of crops and produce is lost due to plant diseases. A significant proportion of these diseases are caused by bacteria, which can both destroy crops and rot produce after harvesting. While this has always been the case, we are still struggling to keep down diseases, often requiring us to fall back to simple solutions such as cultural practices in order to remove infected material or hinder the spread of disease, while chemical solutions which are more effective for large scale agriculture, such as antibiotics or heavy metals are unwanted due to their negative effects on human health and the environment. This lack of good treatments for bacterial diseases has brought back focus on a century-old technology, which in recent years has garnered the attention of researches in the fight against antibiotic resistance (paper 9), bacteriophages. Bacteriophages (or phages) are viruses, which are obligate parasites of bacteria, infecting them in order to replicate their DNA and produce new viral particles. While phages are immensely ubiquitous, we have still not isolated many phages targeting important bacterial plant pathogens, and if we have, we often do not have a lot of information about their interactions. For this reason, phages were isolated, sequenced and characterized for some of the most prominent bacterial plant pathogens, such as bacteria belonging to the Pectobacteriaceae, Pseudomonas syringae and Erwinia amylovora (papers 1-5). The isolated phages were assessed both through bioinformatic characterization in order to classify them and understand their properties, as well as biological assays such as interactions with biofilm and effective host ranges or their ability to reduce disease. As phages might be important in a broader agricultural context, viral-bacterial interactions were also

Lactobacillus plantarum is a bacterium with probiotic properties and promising applications in the food industry and agriculture. So far, bacteriophages of this bacterium have been moderately addressed. We examined the diversity of five new L. plantarum phages via whole genome shotgun sequencing and in silico protein predictions. Moreover, we looked into their phylogeny and their potential genomic similarities to other complete phage genome records through extensive nucleotide and protein comparisons. These analyses revealed a high degree of similarity among the five phages, which extended to the vast majority of predicted virion-associated proteins. Based on these, we selected one of the phages as a representative and performed transmission electron microscopy and structural protein sequencing tests. Overall, the results suggested that the five phages belong to the family Myoviridae, they have a long genome of 137,973-141,344 bp, a G/C content of 36.3-36.6% that is quite distinct from their host's, and surprisingly, 7 to 15 tRNAs. Only an average 41/174 of their predicted genes were assigned a function. The comparative analyses unraveled considerable genetic diversity for the five L. plantarum phages in this study. Hence, the new genus "Semelevirus" was proposed, comprising exclusively of the five phages. This novel lineage of Lactobacillus phages provides further insight into the genetic heterogeneity of phages infecting Lactobacillus sp. The five new Lactobacillus phages have potential value for the development of more robust starters through, for example, the selection of mutants insensitive to phage infections. The five phages could also form part of phage cocktails, which producers would apply in different stages of L. plantarum fermentations in order to create a range of organoleptic outputs.

Pectobacterium atrosepticum is a species of plant pathogenic bacteria responsible for significant losses in potato production worldwide. Pectobacterium atrosepticum can cause blackleg disease on potato stems as well as the tuber disease termed potato soft rot. Methods for the effective control of these diseases are limited and are primarily based on good agricultural practices. Bacteriophages, viruses of bacteria, could be used as an alternative, environmentally friendly, control measure. Here, we describe the isolation and characterization of 29 phages virulent to P. atrosepticum. The phages belong to 12 different species based on a 95% sequence identity cut-off. Furthermore, based on sequence diversity and propagation results, we selected six of these phages to form a phage cocktail. The phages in the cocktail was tested on a number of P. atrosepticum strains in order to determine their host range. The phages was found to lyse 93% of the tested strains. The cocktail was subsequently tested for its effectiveness in combatting potato soft rot under simulated storage conditions. Use of the phage cocktail reduced both disease incidence and disease severity by 61% and 64%, respectively, strongly indicating that phage biocontrol has the potential to reduce the economic impact of soft rot in potato production.