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Applied and Environmental Microbiology, August 2005, p. 4628-4637, Vol. 71, No. 8
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.8.4628-4637.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Mobility of Protozoa through Narrow Channels

Wei Wang,¹ Leslie M. Shor,¹ Eugene J. LeBoeuf,¹ John P. Wikswo,² and David S. Kosson^1*

Department of Civil and Environmental Engineering,¹ Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University, Nashville, Tennessee²

Received 29 September 2004/ Accepted 14 February 2005

Microbes in the environment are profoundly affected by chemical and physical heterogeneities occurring on a spatial scale of millimeters to micrometers. Physical refuges are critical for maintaining stable bacterial populations in the presence of high predation pressure by protozoa. The effects of microscale heterogeneity, however, are difficult to replicate and observe using conventional experimental techniques. The objective of this research was to investigate the effect of spatial constraints on the mobility of six species of marine protozoa. Microfluidic devices were created with small channels similar in size to pore spaces in soil or sediment systems. Individuals from each species of protozoa tested were able to rapidly discover and move within these channels. The time required for locating the channel entrance from the source well increased with protozoan size and decreased with channel height. Protozoa of every species were able to pass constrictions with dimensions equal to or smaller than the individual's unconstrained cross-sectional area. Channel geometry was also an important factor affecting protozoan mobility. Linear rates of motion for various species of protozoa varied by channel size. In relatively wide channels, typical rates of motion were 300 to 500 µm s^–1 (or about 1 m per hour). As the channel dimensions decreased, however, motilities slowed more than an order of magnitude to 20 µm s^–1. Protozoa were consistently observed to exhibit several strategies for successfully traversing channel reductions. The empirical results and qualitative observations resulting from this research help define the physical limitations on protozoan grazing, a critical process affecting microbes in the environment.

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* Corresponding author. Mailing address: Department of Civil and Environmental Engineering, Vanderbilt University, Box 1831 Station B, Nashville, TN 37235. Phone: (615) 322-1064. Fax: (615) 322-3365. E-mail: david.kosson{at}vanderbilt.edu.

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Applied and Environmental Microbiology, August 2005, p. 4628-4637, Vol. 71, No. 8
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.8.4628-4637.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Wang, W., Shor, L. M., LeBoeuf, E. J., Wikswo, J. P., Taghon, G. L., Kosson, D. S. (2008). Protozoan Migration in Bent Microfluidic Channels. Appl. Environ. Microbiol. 74: 1945-1949 [Abstract] [Full Text]