Mutants ofMethylobacterium organophilum unable to synthesize PQQ

The phenotype of mutants unable to synthesize PQQ is analyzed for different categories of methylotrophic bacteria. The advantages offered by strains dissimilating methylamine through methylated amino-acids are discussed. InM.organophilum, 40% of the mutants unable to grow in methanol medium but with normal methylamine utilization, were affected in PQQ metabolism. The genetic properties ofM.organophilum useful to study PQQ mutants are discussed, mainly the use of pSUP106 to create insertion mutations in the bacterial chromosome and to replace wild-type genes by modified genes. An example is given of the possibility to create R plasmids containing large fragments ofM.organophilum DNA. Some physiological properties of a PQQ mutant are described, regarding growth kinetics, PQQ uptake and accumulation.