A total of 342 strains belonging to the genus were examined for cytochrome oxidase activity by using a quantitative colorimetric -tetramethyl--phenylenediamine (TMPD) oxidase assay. The following three oxidase reaction groups were identified: (i) a highly oxidase-positive group, whose members oxidized TMPD with specific activities of more than 0.400 μmol/h per mg (dry weight); (ii) an oxidase-negative group, whose members were incapable of oxidizing TMPD (like ); and (iii) an intermediate group of strains designated the oxidase-indeterminate group, whose members oxidized TMPD at rates just slightly higher than the autooxidation rate. Of 293 mesophilic strains analyzed 23% were oxidase positive, 47% were oxidase indeterminate, and 30% were oxidase negative. Of 37 thermophilic strains, 68% were highly oxidase positive. All of the psychrophiles tested (13 strains) gave oxidase-indeterminate reactions. Spectral analyses of the membranes of 58 strains revealed that there was type cytochrome(s) in all 39 oxidase-positive and oxidase-indeterminate strains. Cytochrome was detected in all 58 strains, 27 strains contained cytochromes and , and 9 strains contained cytochromes , , and The remaining 22 strains contained cytochrome exclusively. Analyses of 19 oxidase-negative strains revealed that 17 lacked type cytochromes; the exceptions were ATCC 14581 (T = type strain) and No. 1. All 19 oxidase-negative strains contained cytochrome ; 11 of these strains also contained cytochromes , 4 strains contained cytochromes , , and , and another 4 strains possessed cytochrome exclusively as the sole terminal oxidase.


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