Various micro-organisms were studied for their thymidine kinase (adenosine 5'-triphosphate: thymidine 5'-phosphotransferase, EC 184.108.40.206) (TK) activity. The sonicated cell extract of Escherichia coli K12 had a TK activity of 35-66 pmol thymidine monophosphate formed min-1 (mg protein)-l. The cell extracts of Salmonella typhimurium and Klebsiella pneumoniae showed a markedly higher (5- to 11-fold) TK activity. Somewhat lower but significant TK activity was detected in the cell extracts of Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis and Proteus mzrabilis. In contrast, weak TK activity, if any, was detected in the cell extracts of Pseudomonas aeruginosa. This was also the case with respect to the cell extracts of various actinomycetes (such as Nocardia and Streptomyces) and related organisms (such as Corynebacterium, Mycobacteriurn and Rhodococcus).
A system is described for the rapid and accurate identification of Bacillus isolates using a matrix of results from tests in the API 20E and API 5OCHB strips and from supplementary tests. API System tests have been shown to be more reproducible than the classical tests. A taxonomy based upon API tests is in good agreement with those obtained by other methods. The results matrix can also be used in computer assisted identification.