In the second of this Video Gallery series we show two video clips taken by Edward Cowen, UK. The video clips show the intriguing movements of Spirochaetes which are bacteria (phylum Spirochaetae) characterised by their corkscrew shape.

Obtaining video sequences of bacteria is quite a challenge as many bacteria are only a few micrometres long and demand the highest power objectives. The sequences shown are aquatic bacteria and use Edward's home adapted phase contrast outfit at high magnification (100x, NA1.3 oil immersion objective).

As an aside not all bacteria are very small i.e a few microns, there are some species that are fractions of a millimetre in diameter. The largest found to date, a bacterium 0.75mm across, was recently reported in the press and is thus just visible to the naked eye. The full illustrated paper on this bacterium is in the April 16th 1999 edition of the magazine 'Science' (use Search routine with 'bacteria' and 'Schulz' together as keywords, a small fee is charged for non-subscribers).

Original video clip six seconds at 5 frames/second, continuous loop.  This version has a limited 256 colour palette. This first video clip shows an intriguing dance between two Spirochaete bacteria taken using darkfield illumination.

Original video clip four seconds at 5 frames/second, continuous loop.  This version has a limited 256 colour palette. This second video clip using phase contrast lighting gives an indication of the teeming mass of bacteria that can occur in many habitats. Although some bacteria are harmful to man, many aren't and we could not live without their vital role eg. in breaking down organic matter and cycling various elements essential to man such as nitrogen.

Comments to Edward Cowen welcomed.

Further information

A well illustrated book showing the various types of bacteria is 'Five Kingdoms' by L. Margulis and K. V. Schwartz, publisher W H Freeman (third edition 1998). Multimedia encyclopaedias should also give a good overview. There are also many web sites describing and illustrating bacteria, a web search engine with appropriate keywords should list them.