Metagenomics of bacteria and bacteriophages in ants and their nests

Humans face continual threats from disease-causing microorganisms, complicated by the rising threat of antibiotic resistance. Ant and human societies share features including large populations, close living quarters, self-medication, hygiene practices, and antibiotic use for infection control. The eusocial lifestyle of ants increases the risk of disease transmission. However, unlike humans grappling with antimicrobial resistance, ants seemingly thrive without succumbing to bacterial pathogens in their natural habitats. Within their 150 million years of evolution, ants have likely developed effective mechanisms to cope with diseases, and their cultivated microorganisms may be important. Viruses infecting bacteria – bacteriophages - are emerging as key players in bacterial population dynamics and evolution, and are potential therapeutic agents. However, the study of phages in the natural environment remains in its infancy, particularly in the context of the approx. 13,000 ant species and their nests. This thesis explores the intricate relationships between ants, bacteria, and bacteriophages. The findings reveal insights into the microbiome of the red wood ant (Formica rufa), indicating that geographical location and habitat significantly influence the diversity and composition of associated microbial communities. Predominant bacterial taxa in worker abdomens, potentially constituting a core microbiome, include Wolbachia, Streptomyces, Acetobacteracae, and Lactobacillus. Of particular interest, Streptomyces, a valuable source ofnew antibiotics, were abundant in nest material and could play a role in disease resistance. The thesis presents whole-genome sequences of 12 bacteria isolated from Formica rufa and their nests, highlighting prophages and biosynthetic gene clusters. Inhibitory effects of major chemical components from red wood ant venom are identified. Additionally, an unexplored bacteriophage community in 17 species of Cephalotes turtle ants is reported, unveiling many novel phage sequences, including complete genomes. These results enhance understanding of microbial community diversity associated with social insects, opening avenues to explore microbe-host interactions and adaptations within the context of social evolution.