Three main genera make up the bacterial population of ke r: lactobacilli, lac- tococci, and leuconostoc. A fourth genus, acetobacter, is also often mentioned, but its presence is not reported by all research teams studying ke r. Some teams even pose the questions as to whether acetobacter could be a contaminant.12 Studies in our laboratory did demonstrate the presence of acetobacter in ke r, but the relatively low numbers could explain why other teams could have missed them.13 A suitable selec- tive medium for this genus is essential for its isolation.