How Giardia swim and divide

To determine how binuclear giardia swim, we used video microscopy to observ e trophozoites of Giardia intestinalis, which were labeled with an amino-sp ecific Alexa Fluor dye that highlighted the flagella and adherence disc. Gi ardia swam forward by means of the synchronous beating of anterior, postero lateral, and ventral flagella in the plane of the ventral disc, while cauda l flagella swam in a plane perpendicular to the disc. Giardia turned in the plane of the disc by means of a rudder-like motion of its tail, which was constant rather than beating. To determine how giardia divide, we used thre e-dimensional confocal microscopy, the same surface label, nuclear stains, and antitubulin antibodies. Giardia divided with mirror-image symmetry in t he plane of the adherence disc, so that the right nucleus of the mother bec ame the left nucleus of the daughter. Pairs of nuclei were tethered togethe r by microtubules which surrounded nuclei and prevented mother or daughter giardia from receiving two copies of the same nucleus. New, adherence discs formed upon a spiral backbone of microtubules, which had a clockwise rotat ion when viewed from the ventral surface. These dynamic observations of the parasite begin to reveal how giardia swim and divide.