A Quantitative Assay of Group E Colicins
Smarda, J., Damborsky, J.
SCRIPTA MEDICA 64: 111-118 (1991)
Two basic methods of quantitative assay of the inhibitive activity of colicins towards bacteria are commonly used in a variety of modifications: the critical dilution spot test and survival count. The former gives the colicin activity in arbitrary units (A.U.), the latter in lethal units (L.U.). In a series of experiments, the two titration methods were compared for all colicins of Group E, namely E1-E9, using Escherichia coli K12-Row indicator bacteria. For all colicins, the L.U. to A.U. ratio equals 2×10^8:1. 1A.U. comprises 2×10^8 L.U. Both advantages and disadvantages, especially the possible error sources, of either colicin titration procedure are briefly discussed. It is emphasized that any colicin titre value match the assay system used.