Development of the fly crop vessel bioassay for fly/microbial studies

The dipteran crop has been implicated in many fly/microbe associations. In most cases, reports merely identify that the microbe(s) in question is(are) found inside the crop, but very few studies have focused on their long-term presence within the crop. Possibly, one of the main reasons for this is that flies usually regurgitate their crop contents, which makes it difficult to do long-term studies. Because of this, an in situ crop vessel bioassay was developed using adult Musca domestica as the crop donor and Escherichia coli are the microbe of choice. Procedures for crop filling, removal, sanitization and crop microbial contents over a 48 h incubation period were evaluated. Even though biofilm formation was suggested based on the microscopy, an increase in numbers was not observed, which possibly indicates there was no biofilm formed. This assay can be amended to fit any fly/microbe association in which one wants to study the microbe within the crop without its contents being regurgitated.