Spirochaete-mediated abnormal sex-ratio (SR) condition in Drosophila: A second virus associated with spirochaetes and its use in the study of the SR condition

Abstract

SUMMARYA class of abnormal sex-ratio (SR) condition in Drosophila characterized by the elimination of male zygotes is caused by infection with maternally transmitted SR-spirochaetes. A given spirochaete strain, WSR, was shown to have an associated DNA virus, spv-2, in a latent condition. This virus is induced to multiply when another DNA virus, previously designated spv-1, infects WSR spirochaetes; spv-1 is normally associated with another strain of SR-spirochaetes, NSR, and is in a manifest state. Spv-2 infects and lyses NSR, thus eliminating spirochaetes from fly hosts which, in these experiments, were D. melanogaster.The elimination of WSR through lysis by spv-1 results in the ‘curing’ of the SR-condition in the host flies. However, the elimination of NSR by spv-2 does not lead to the immediate elimination of the SR-condition in the host. A hypothesis is presented in favour of the view that a substance, androcidin, is produced by SR-spirochaetes and that this substance is actually responsible for the death of male zygotes. NSR may produce a more potent androcidin than WSR.