By mapping the entire genome of a bacterium that infects a close relative of the fruit fly, scientists at Uppsala University have found that gene exchange is widespread among this sex-manipulating bacteria.
The finding paves the way for using sex-manipulating bacteria as environmentally friendly pesticides against harmful insects.
Bacteria belonging to the Wolbachia group are adapted to invertebrate animals like insects, spiders, scorpions, and worms. They have learned to manipulate the proportion of females and males in insect populations.
The bacteria spread via the female's eggs from one generation to the next, and manipulate the sex quotas among the infected animals, so that more females are produced in the population.
This means that the bacteria convert genetic males into females or kill male embryos that are then eaten by their sisters or make females lay unfertilised eggs that all become females.
However, very often males cannot reproduce with non-infected females, which gives an edge to the infected females and the infection spreads rapidly among the population.
By studying the whole genome, the researchers have shown that these bacteria carry genes that are common among higher organisms, but rare among other bacteria.
According to the scientists, the bacteria have stolen these genes from the genome in the host cell, and that they now use them to manipulate the sex quotas among the insects.
"With the help of viruses, these bacteria exchange genes with each other, which leads to a rapid dissemination of genes that are thought to be important for sex manipulation," said Lisa Klasson, one of the researchers behind the study.
The researchers have shown that the genomes of these bacteria are evolutionary mosaics consisting of DNA pieces from many closely-related bacteria.
This causes each gene to have its own evolutionary history, and thus the potential for variation is infinite.
"It's fascinating that bacteria, with only 1,000 genes, can control complicated developmental processes and behaviors in insects," said Siv Andersson.
By mapping how the genes in the bacteria change over time, and figuring out the mechanisms behind sex manipulation, the scientists may be able to lay a foundation for finding new pesticides for insects, based on nature's own principles.
The study has been published in PNAS.