Homology of the gene coding for outer membrane lipoprotein within various Gram-negative bacteria

The mRNA for a major outer membrane lipoprotein from Escherichia coli was found to hybridize specifically with one of the EcoRI and one of the HindIII restriction endonuclease-generated fragments of total DNA from nine bacteria in the family Enterobacteriaceae: E. coli, Shigella dysenteriae, Salmonella typhimurium, Citrobacter freundii, Klebsiella aerogenes, Enterobacter aerogenes, Edwardsiella tarda, Serratia marcescens, and Erwinia amylovora. However, among the Enterobacteriaceae, DNA from two species of Proteus (P. mirabilis and P. morganii) did not contain any restriction endonuclease fragments that hybridized with the E. coli lipoprotein mRNA. Furthermore, no hybrid bands were detected in four other gram-negative bacteria outside the family Enterobacteriaceae: Pseudomonas aeruginosa, Acinetobacter sp. HO1-N, Caulobacter crescentus, and Myxococcus xanthus. Envelope fractions from all bacteria in the family Enterobacteriaceae tested above cross-reacted with antiserum against the purified E. coli free-form lipoprotein in the Ouchterlony immunodiffusion test. Both species of Proteus, however, gave considerably weaker precipitation lines, in comparison with the intense lines produced by the other members of the family. All of the above four bacteria outside the family Enterobacteriaceae did not cross-react with anti-E. coli lipoprotein serum. From these results, the rate of evolutionary changes in the lipoprotein gene seems to be closely related to that observed for various soluble enzymes of the Enterobacteriaceae.