FIG. 4.

In situ detection and morphology of endosymbiotic bacteria in P. grassii. The specific probe CfPt-729 (A and D) labeled with 6-FAM and the eubacterial consensus probe labeled with Texas Red (B) were used simultaneously. (C) Phase-contrast micrograph of the same sample. The protist species are labeled P (Pseudotrichonympha grassii), S (Spirotrichonympha leidyi), and H (Holomastigotes mirabile). Panel D is a magnified view of endosymbiotic bacteria in P. grassii detected with probe CfPt-729. The green fluorescence derived from the probe labeled by 6-FAM enabled us to distinguish the positive signals from amorphous yellow backgrounds of autofluorescence or wood particles in the gut. (E) Transmission electron micrograph of the endosymbionts (indicated by arrowheads) in a P. grassii cell. Probable hydrogenosomes of the host protist are labeled H. The scale bars in panels C, D, and E are 100 μm, 10 μm, and 1 μm, respectively.