The persistence of a microbial flora during postembryogenesis of Drosophila melanogaster
Abstract
The "infection" mechanism whereby bacteria on the surface of the egg of Drosophila melanogaster "infect" larvae has been indirectly determined to result from young larvae eating the chorion (or off the chorion) of the egg. There was no evidence that bacteria occur within the egg. A bacterial flora was shown to persist through larval and pupal development in two wild-type stocks of Drosophila having different gram-positive floras. Further studies with an Escherichia coli-infected stock have shown that E. coli persists during the development of the insect only when monoxenic; it is replaced within 1 week after exposure to normal flora. Bacteria may be excluded from the developing imago about the time of hypoderm formation, although adult flies removed from all contamination except that present in the pupal case did maintain a bacterial flora. The two wild-type stocks were monoxenically infected with a member of their own flora, or with a foreign bacterium, or were left axenic. The length of the larval period in the stocks of Drosophila used was significantly shorter when they were infected with a member of their own flora than it was when they were axenic. The length of the larval period when stocks were monoxenically infected with a foreign bacterium was significantly longer than when a member of the normal flora was present. Studies of eggs removed from females under sterile conditions indicate that contamination of the chorion surface occurs via the feces. The persistence of bacteria in all stages of development, the inability of E. coli to remain with these stocks, and the shortened developmental time in the presence of normal flora suggests that the microbial flora studied is mutualistically symbiotic, and may be genetically determined.
- Publication:
-
Journal of Invertebrate Pathology
- Pub Date:
- January 1969
- DOI:
- 10.1016/0022-2011(69)90163-3
- Bibcode:
- 1969JInvP..14..365B