The full text of the article Crystal River cited is here:

http://hic.sagepub.com/content/4/3/2324709616662671.full.pdf

However, it does not identify the spirochetes in question. This is apparently because colonic spirochetes have in the past generally been found to be Brachyspira species, most often Brachyspira pilosicoli (also called Serpulina pilosicoli). These are thought to usually be commensal (i.e. benign), and surprisingly can be found in 2% to 7% of the general population in Western countries. Despite this, quite frequently when these are found, metronidazole is prescribed to the patient, if there is thought to be any chance that adverse symptoms are due to the spirochete. Metronidazole can have nasty side effects in some people.

I get the impression that usually when colonic spirochetes are found, they are not actually further identified, but just assumed to be Brachyspira. In this age of increasing Borrelia (Lyme) incidence, this may be naive.

I got most of this information from another article, but it is not a free journal so I can only post a link to the abstract:

http://www.ncbi.nlm.nih.gov/pubmed/15095857