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Infection and Immunity, December 2001, p. 7866-7872, Vol. 69, No. 12
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.12.7866-7872.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

How Giardia Swim and Divide

Sudip Ghosh,¹ Marta Frisardi,¹ Rick Rogers,² and John Samuelson^1,*

Department of Immunology and Infectious Diseases¹ and the BioMedical Imaging Institute,² Harvard School of Public Health, Boston, Massachusetts 02115

Received 14 November 2000/Returned for modification 20 December 2000/Accepted 25 August 2001

To determine how binuclear giardia swim, we used video microscopy to observe trophozoites of Giardia intestinalis, which were labeled with an amino-specific Alexa Fluor dye that highlighted the flagella and adherence disc. Giardia swam forward by means of the synchronous beating of anterior, posterolateral, and ventral flagella in the plane of the ventral disc, while caudal 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 three-dimensional confocal microscopy, the same surface label, nuclear stains, and antitubulin antibodies. Giardia divided with mirror-image symmetry in the plane of the adherence disc, so that the right nucleus of the mother became the left nucleus of the daughter. Pairs of nuclei were tethered together 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 rotation when viewed from the ventral surface. These dynamic observations of the parasite begin to reveal how giardia swim and divide.

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^* Corresponding author. Mailing address: Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115. Phone: (617) 432-4670. Fax: (617) 738-4914. E-mail: jsamuels{at}hsph.harvard.edu.

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Infection and Immunity, December 2001, p. 7866-7872, Vol. 69, No. 12
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.12.7866-7872.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

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