Letters in Applied Microbiology zyxwvutsrqpo 1994, zyxwvutsrq 19, 401-405 Transfer of Nocardia amarae Lechevalier and Lechevalier 1974 to the genus Gordona as Gordona amarae comb. nov. M. Goodfellow, J. Chun, S. Stubbs’ and A. S. Tobili Department of Microbiology, The Medical School, Newcastle-upon-Tyne and ‘Department of Microbiology, BBSRC Institute of Food Research, Reading Laboratory, Reading, UK GWG/260: received 19 May 1994 and accepted zyxwvuts 5 July 1994 M. GOODFELLOW, J. CHUN. S. STUBBS AND A.S. TOBILI. 1994. zyxwvu The taxonomic status of Nocardia amarae strains was examined using chemical, microbiological and nucleic acid sequencing methods. It was evident from the results of this and previous studies that Nocardia amarae has properties that are at variance with its classification in the genus Nocardia but consistent with its transfer to the genus Gordona. It is proposed that Nocardia amarae Lechevalier and Lechevalier 1974 be transferred to the genus Gordona as Gordona amarae comb. nov. INTRODUCTION Norcardia amarae was proposed by Lechevalier and Lech- evalier (1974) for novel actinomycetes isolated in large numbers from foam on the surface of aeration tanks in activated-sludge sewage-treatment plants. The organism, which contained meso-diaminopimelic acid, arabinose and galactose (wall chemotype IV sensu Lechevalier and Lech- evalier 1970) and mycolic acids, was considered to be closely related to actinomycetes subsequently classified in the genus Rhodococcus (Tsukamura 1974; Goodfellow and Alderson 1977). Similarly, some rhodococci were later assigned to the genera Gordona (Stackebrandt et zyxwvutsrq al. 1988) and Tsukamurella (Collins et al. 1988) leaving the genus Rhodococcus as a homogeneous taxon. Mycolic acid containing actinomycetes have many properties in common, form a distinct phyletic group and are assigned to the genera Corynebacterium, Cordona, Myco- bacterium, Nocardia, Rhodococcus and Tsukamurella pri- marily on the basis of chemical and morphological markers (Goodfellow 1992). It has been clear for some time that the continued inclusion of N. amarae in the genus Nocardia is debatable. (Goodfellow and Pirouz 1982). Unlike true nocardiae, N. amarae has dihydrogenated menaquinone with nine isoprene units (MK-9[H2]) as the major iso- prenologue, is resistant to nocardiophage, does not grow in lysozyme broth, and releases C,, and zyxwvutsr CI8 monosaturated esters on pyrolysis of methyl mycolates (Lechevalier and Lechevalier 1974; Williams et al. 1980; Goodfellow et al. 1982). The organism has also been distinguished from Nocardia sensu strict0 in numerical phenetic (Good fellow and Pirouz 198a) and serological analyses (Ridell 1984). In Correspondence to : Pr($essor M. Good/i.llow, Department zyxwvutsrqp of MicrobioloRy, zyxwvutsrqpon The Medical School, Framlington Place, Newcastle-upon-Tyne NE2 4HH, zyxwvutsrq UK. more extensive numerical phenetic surveys, N. amarae strains were sharply distinguished from aggregate groups corresponding to the genera Rhodococcus and Tsukamurella (Cordona aurantiaca) but formed a homogeneous cluster at the edge of an aggregate taxon equated with the genus Nocardia (Goodfellow and Pirouz 1982; Goodfellow et al. 1982). The aim of the present study was to clarify the tax- onomic position of Nocardia amarae. MATERIALS AND METHODS Test strains All four N. amarae strains, namely N667(Se 6; type strain), N775(Se 64), N779(Se 100) and N787(Se 291), were iso- lated from foam found in sewage plants in the USA (Lechevalier and Lechevalier 1974). The strains were main- tained on glucose yeast extract agar (GYEA; Gordon and Mihm 1962) and as glycerol suspensions (20%, v/v) stored at - 20°C. Lipid analyses The test strains were grown in shake culture at 30°C for up to 7 d in modified Sauton’s medium (Mordarska et al. 1972), checked for purity at maximum growth, killed by shaking overnight with formalin (1 O/O, v/v), separated by centrifugation, washed with distilled water and freeze- dried. Isoprenoid quinones were extracted and purified from freeze-dried biomass (ca 50 rng) using the procedure described by Minnikin et al. (1984). Purified menaquinones were separated by high-performance liquid chromatography using a Pharmacia LKB instrument fitted with a Spher- isorb ODS column (5 pm). Acetonitrile-isopropanol