“Mycobacterium” rhodochrous の分類学的研究

“Mycobacterium” rhodochrous の新しいgenus Gordona へのくみいれ

抄録

“Mycobacterium” rhodochrous is being regarded as an intermediate organism between Mycobacterium and Nocardia, but its taxonomic position is not yet established. The present study has been designed to elucidate the taxonomy of this mysterious organism. Previously, the present author isolated flinty strains of “Mycobacterium” rhodochrous-like organisms from sputa of patients and soils. The organisms showed intermediate characters between Mycobacterium and Nocardia and were considered to be a new genus, Gordona. The Gordona was considered to belong to family Mycobacteriaceae, as the organisms showed slight acid-fastness and lacked mycelium. At that time, it was pointed out that the organisms have common features with “M.” rhodochrous ATCC 13808 in respect to distinguishing characters which differentiate Mycobacterium (rapid-growing mycobacteria) from Nocardia. This finding suggested that the organisms and “M.” rhodochrous belong to the same genus. In the present study, characters of 6 strains of “M.” rhodochrous were compared with those of Gordona, Mycobacterium, Nocardia and Mycococcus. The methods used for testing were described previously
1. Characters of 6 strains of “M.” rhodochrous are shown in Tables 1 to 5 together with those of 3 representative strains of Gordona and 1 strain of Mycococcus. Strain BKM B-963 of Mycococcus luteus is only strain of genus Mycococcus being maintained in the All Union Collection of Microorganisms, Moscow.
2. As seen in Tables 1 to 5 and in Tables 6 and 7, the characters of Mycococcus luteus are significantly different from those of strains of Gordona and “M.” rhodochrous. As seen in S-values shown in Table 6, the characters of the strains of “M.” rhodochrous differed from strain to strain, and difference between the strains was often greater than difference (S-value less than 85%) between the species of Mycobacterium and of Nocardia. Among strains of Gordona, strain NCTC 10669 of G. rubra and strain NCTC 10669 of G. terrae show a S-value of 93% in Table 6. Even these two species showing such S-value could be differentiated by numerical method showing a statistically significant difference. Thus, the result shown in Table 6 seems to suggest that the “M.” rhodochrous strains have heterogenous characters ascomparable as different species.