Actually a white blood cell chasing bacteria. Entertaining video.
http://www.thinkgene.com/white-blood-cell-chasing-bacteria/
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Richard Kennaway, jrk@cmp.uea.ac.uk, http://www.cmp.uea.ac.uk/~jrk/
School of Computing Sciences,
University of East Anglia, Norwich NR4 7TJ, U.K.