Genome dynamics of protective bacterial symbionts in insects

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Insects, bacteria and viruses outnumber most organisms on earth in both diversity and abundance by several orders of magnitude. This study will examine the evolution and maintenance of a symbiosis that occurs between aphids, the bacterium Hamiltonella defensa, and a bacterial virus (phage). Parasitoid wasps are commonly used as a biological control to mediate agricultural damage caused by aphids. However, aphids infected with H. defensa and the phage are resistant to parasitoid wasps. Preliminary data revealed that the bacteria and the phage have genes encoding many virulence factors, including toxins that have been found in human pathogens. Analyses of bacteria and phage genome sequences and of gene expression will elucidate which virulence factors are conserved and are involved in protecting aphids.This study has implications for the control of insect pests. An understanding of H. defensa biology will also help in refining the ability to predict efficacy of biological control using parasitoid enemies. More generally, bacterial and phage-borne insecticidal toxins may have broader use or interest as means of biological control of crop pests. In addition, this work will continue to provide mentorship and training in molecular biology and bioinformatics for female and minority undergraduate students.