Ultrastructural effects of macrotetrolides of Streptomyces griseus LKS-1 in tissues of Culex pipiens larvae.

The isolate of macrotetrolides produced by Streptomyces griseus strain LKS-1 was tested in its effect on the ultrastructure of larvae of Culex pipiens autogenicus. Changes were mainly in mitochondria where the cristae were destroyed and the outer membrane inflated. The endoplasmic reticulum was vacuolized and subsequently the nuclear membranes were seriously affected. Microvilli of the midgut epithelial cells and the surface membrane of these cells were unaltered and there were no changes in the arrangement of cells in the tissues. The effect of macrotetrolides on insect tissues is analogous to the effect of secondary metabolites of fungi such as beauvericin, destruxin E, cyclosporin or tolypin, and differs from the effects of bacterial endotoxins of Bacillus thuringiensis or B. sphaericus.