The taxonomic position of Obesumbacterium proteus, a common brewery contaminant.

Abstract

SUMMARY: The mole fraction of guanine plus cytosine in the DNA from Obesumbacterium proteus was 48%, similar to that of Hafnia alvei, Salmonella gallinarun and the RM bacterium. DNA:DNA competition studies indicated that O. proteus strains fall into two groups, both of which could reasonably be included in the family Enterobacteriaceae. The same two groups were apparent from a numerical taxouomic investigation of 19 O. proteus strains which included 16 brewery isolates. The simple matching coefficients (%S) were calculated from results of 50 biochemical and taxonomic tests, and a dendrogram was constructed. Every O. proteus isolate had the characteristics of the family Enterobacteriaceae. The two subgroups united at 86% S, and formed a cluster with Hafnia and Salmonella strains at 72.5%. S. The difference between Hafnia alvei and O. proteus was almost entirely due to their different vigour rating. Furthermore, in a simulated brewery fermentation, two strains of H. alvei grew in a mixed culture with yeast. This was originally the defining characteristic of the genus Obesumbacterium. We propose that reference to the genus Obesumbacterium should be discontinued, and that O. proteus should be placed in the genus Hafnia as Hafnia protea comb. nov.