[Bacteria-cortical symbionts of Thichonympha turkestanica, a protozoan from the gut tract of the termite Hodotermes margabicus].

Intracellular symbiotic bacteria of the flagellate Trichonympha turkestanica located in the surface cortical part of the animal cell are described. The cell structure of the symbionts is typical of gramnegative bacteria, but contains also an additional outer membrane. The membrane is an element of the electron-dense structures which have contacts, at many points, with the kinetosomes or membranes surrounding flagella. A possible functional significance of symbiotic bacteria for the operation of flagella is discussed.