Description

Genetic mapping is a valuable tool for determining the location of an allele on a chromosome that is responsible for a given phenotype. This tool provides helps identify a specific mutant gene in a population that may provide a benefit or burden to an organism. We discovered that a natural bacterial pathogen, Bordetella atropi, of the nematode Oscheius tipulae can infect the animal’s intestine and use filamentation (long threads) to spread between host cells. Here, we have found through infection of a panel of wild isolates of O. tipulae that there is a range of natural resistance and susceptibility to B. atropi infection. The wild strain of O. tipulae that had the most resistance against the intracellular bacteria was designated JU457, which showed a less than 2% infection rate, compared to a greater than 70% infection rate seen in wild-type O. tipulae. These divergent infection phenotypes will allow us to use genetic mapping to identify the resistance gene in this JU457 strain. Overall, researching this resistance against bacterial infection in nematodes could reveal conserved paradigms regarding how humans combat and resist bacterial infections. In order to map JU457 resistance to B. atropi, we performed a mating experiment to verify it can mate with a susceptible strain. We found that males of JU457 were capable of mating with hermaphrodites of CEW1, which will allow us to mate the strains and challenge their F2 progeny on the pathogen. In order for the mapping to work, we needed to verify that JU457 survives better than CEW1 when infected with B. atropi. We indeed discovered that JU457 worms survived the infection. By contrast, all of the CEW1 worms were susceptible to the infection and died off. This confirmed that JU457 not only shows less infection than wild-type animals but in fact survived B. atropi infection better. Based on these observations, we strongly believe that the JU457 strain is more resistant to this bacterial infection, allowing us to use genetic mapping to identify a resistance gene to intracellular bacterial infection.