Fig. 3.

Spirochete round bodies (RBs). (A) BacLight preparations vital stain. RBs formed from healthy spirochetes after 5 wk suspension in dH₂O in 0.05 μg/mL TG. The red stain indicates that the material is dead. Whereas a few green cores and spirochetes in the RBs seen at TG concentrations of 0.05 μg/mL or less indicate some viability after 5 wk, those few RBs with green cores are entirely reversible. (Scale bar: 4 μm.) (B) Five-day-old RBs after suspension of healthy spirochetes in dH₂O-acridine orange stain at pH 6.4, flame-fixed. The red-orange stain color indicates the RNA of healthy spirochetes. They do not yet show core structures; the outer membrane is not visible. Core structures develop only in viable, nondegenerating living organisms >1 wk old. (Scale bar: 8 μm.) (C) Five-week-old RBs after suspension of healthy spirochetes in dH₂O at pH 6.4 acridine orange flame fixed as in B. The red-orange stained RBs show the RNA of these viable propagules that are fully capable of reversion to helical spiral swimmers. Cell division of the core structures inside the RBs leads to proliferation of spirochetes that are not in the motile, helical form. (Scale bar: 10 μm.) (D) RBs originally incubated in lethal quantities of TG for 5 wk. Shown is BacLight vital stain. The red stain indicates that the material is dead. Neither spirochetes nor green color (here) was visible in any cultures treated with TG at concentrations >0.05 μg/mL. (Scale bar: 5 μm.) (E) Two RBs in electron micrographic preparation reveal spirochetes and flagella (F) beneath the outer membrane, healthy cell walls and the gradual formation of core structures (CS). When replaced into growth media under favorable environmental conditions, helical, motile spirochetes leave the RBs and swim away. (Left) Young RB reveal numerous spirochetes and flagella inside healthy cell walls and a beginning formation of a core structure. (Right) Old RBs with several core structures, healthy cell wall, and numerous flagella. (Scale bar: 450 nm.)