Time to death in the presence of E. coli: a mass-scale method for assaying pathogen resistance in Drosophila

Abstract

There is now increasing realization that tradeoffs between parasite or pathogen resistance and other life-history related traits could play an important role in shaping life-history evolution (Sheldon and Verhulst 1996; Zuk and Stoehr 2002), and a few experimental studies have examined such tradeoffs in Drosophila (Hoang 2001; Kraaijeveld et al. 2001; McKean and Nunney 2001) and other insects (Moret and Schmidt-Hempel 2000; Hosken 2001; Adamo et al. 2001; Cotter et al. 2004). D. melanogaster has a well-developed innate immune system that is well characterized genetically (Rutschmann et al. 2000; De Gregorio et al. 2001; Irving et al. 2001) and involves phagocytosis, melanization and production of antimicrobial peptides (Elrod-Erickson et al. 2000; Hoffmann 2003). Given that it is also one of the best studied model systems for life-history evolution (Prasad and Joshi 2003), D. melanogaster is an attractive choice for studies on life-history related tradeoffs involving the immune system (Sharmila Bharathi et al. 2004). A potential limitation in using D. melanogaster for rigorous evolutionary experimentation on immune function tradeoffs with life-history related traits is that neither the commonly used infection technique (pricking the fly with a contaminated needle: ElrodErickson et al. 2000; Rutschmann et al. 2000; De Gregorio et al. 2001; McKean and Nunney 2001), nor the typical assays for immune competence (e.g. rate of clearing of pathogen: McKean and Nunney 2001; level of antimicrobial peptides induced: Rutschmann et al. 2000; extent of phagocytosis: