To survive a bacterial

Fly blood does not normally contain substances that kill bacteria, but flies inoculated with bacteria rapidly accumulate antibacterial proteins (ABs) in their blood. Wild type Drosophila have at least three different antibacterial proteins based on isoelectric points. Genetic variants identify structural genes for these antibacterial proteins. A DNA sequence that can encode a conserved portion of moth and fleshfly antibacterial proteins has been used to synthesize a complementary oligonucleotide probe. This probe recognizes a messenger RNA that appears in the fat body of Drosophila and Medflies only after they have been inoculated with bacteria. Bacteria-sensitive lethal mutations were induced to identify genes necessary for flies to survive a bacterial infection. 

This communication reports studies on the humoral antibacterial response in Drosophila and Ceratitis capitata, the Mediterranean fruit fly. The goal of our work is to understand the molecular mechanisms that protect flies from bacterial infection. Here we examine three questions 1) What genes encode antibacterial proteins 2) Does the antibacterial response involve the accumulation of new messenger RNAs And 3), what genes are necessary to survive a bacterial attack Answers to these questions will help us to determine the potential of blocking the immune system to control populations of insect pests. 

From our bacteria sensitive lethal mutations we can make the surprising conclusion that the presence of ABs detected after overlaying an isoelectric focusing gel with bacteria is insufficient for a fly to survive a bacterial attack. Therefore, at least some of our bsl mutations identify genes required for surviving a bacterial infection that are independent of the ABs. We hypothesize that the necessary function identified by the bsl mutants is a cellular immune function, perhaps phagocytosis of bacteria. 

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