Characterization of a new methylotrophic strain,Methylomonas clara

Summary The organism examined was identified as an obligate methylotroph and as an organism of type I, because it has some characteristics of this group: methanol is utilized via the hexulose phosphate pathway, the enzymes glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, malate dehydrogenase, and isocitrate dehydrogenase (both NAD- and NADP-specific) could be detected, whereas the citric acid cycle is incomplete (in particular -ketoglutarate dehydrogenase could not be found). Furthermore, the organism is able to fix nitrogen. In contrast, there are some different characteristics: carbon dioxide can be fixed in connection with methanol. There is no formate dehydrogenase, and formaldehyde dehydrogenase can be induced by different culture conditions. Moreover, the GC content (49.2%) is distinctly lower than normal, and the hexulose phosphate synthase shows a higher activity with NAD as cosubstrate than with NADP. Carbon is not metabolized via the Embden-Meyerhoff-Parnaß pathway, but via the Entner-Doudoroff pathway. In the disk test, the organism is resistant to some antibiotics: chloramphenicol, fusidic acid, methicillin and lincomycin. A partial resistance can be observed with penicillin, neomycin, novobiocin, and cloxacillin.