Plant diseases significantly impact crop yields and quality, resulting in billions of dollars in losses annually in the United States. Diseases, which can reduce productivity, degrade quality, and contaminate food supplies, are caused by various living organisms, including fungi, bacteria, viruses, and nematodes. Soil-dwelling organisms and microbes, such as insects, bacteriophages, bacteria, mites, and fungal vectors, play critical roles in either exacerbating or mitigating plant diseases. To develop effective disease control strategies, it is essential to understand the biology and interactions of these soil organisms. Bacteriophages are key drivers of microbial community dynamics, influencing diversity, richness, abundance, evolution, and bacterial physiology within a given habitat. Over the past two decades, they have been extensively studied for their roles in antimicrobial resistance, food safety, food processing, agriculture, environmental sustainability, and medicine. However, despite their recognized importance, much remains unknown about how phages regulate bacterial populations in complex natural ecosystems, particularly in soil environments.

In their new study titled "Dolichocephalovirinae Phages Exist as Episomal Pseudolysogens Across Diverse Soil Bacteria", former graduate student Dr. Tannaz Mohammadi and her mentor Dr. Bert Ely characterized the giant bacteriophages found within diverse soil bacteria and 14 additional phages isolated directly from soil samples. They found that these phages are giant phages with genome sizes around 200 kb that exist in their host bacteria as episomes.