Spirochetes

The Spirochetes stain Gram-negative but form a different phylum from Escherichia coli and close relatives. They are highly helical and motile in shape with an unusual form of motility using endoflagella. The most well-known example of this phylum is Treponema pallidum that causes syphilis; however, the majority is free-living or obligately symbiotic nonpathogenic organisms. T. pallidum cannot be grown as a free- living organism in the laboratory but must be grown with animal cell culture. The other notable pathogen from this phylum is Borrelia burgdorferi which causes the tick-borne Lyme disease.