INTERNATIONAL
JOURNAL
OF SYSTEMATIC
BACTERIOLOGY,
July 1987, p. 287-288
0020-7713187103287-02$02.OO/O
Copyright 0 1987, International Union of Microbiological Societies
Vol. 31, No. 3
Transfer of Arthrobacter variabilis (Muller) to the Genus
Corynebacterium, as Corynebacterium variabilis comb. nov.
MATTHEW DAVID COLLINS
Department of Food Microbiology, AFRC Institute of Food Research, Shinfield, Reading RG2 9A T, England
Arthrobacter variabilis (Miiller) differs so much from the type species of the genus Arthrobacter, Arthrobacter
globiforrnis, that it should not be retained within this genus. On the basis of biochemical and chemical criteria,
it is proposed that Arthrobacter variubilis be reclassified in the genus Corynebacterium, as Corynebacterium
vuriubilis comb. nov. The type strain is ATCC 15753 (NCIB 9455).
The species Arthrobacter variabilis was originally isolated
from animal fodder and assigned to the genus Arthrobacter
by Miiller in 1961 (7). The placement of this species in the
genus Arthrobacter has always been controversial, and
recent chemotaxonomic studies clearly indicate that this
microorganism should be reclassified in the genus Corynebacterium (1, 2, 6, 8, 10). It is now universally accepted that
the genus Arthrobacter should be restricted to those species
which possess a murein based on L-lysine ( 5 ) . A. variabilis
differs from true arthrobacters in possessing a directly crosslinked murein based on meso-diaminopimelic acid (6, 8), a
type consistent, however, with the genus Corynebacterium
(1). The wall of A . variabilis also differs from that of true
arthrobacters but is similar to that of Corynebacterium spp.
in containing an arabinogalactan polymer (6). Support for the
inclusion of A . variabilis in the genus Corynebacterium also
comes from the reports of short-chain mycolic acids (30 to 36
carbon atoms) and predominantly straight-chain saturated,
mono-unsaturated, and 10-methyl-branched long-chain fatty
acids in this species (1, 2). True members of the genus
Arthrobacter lack mycolic acids and contain predominantly
straight-chain saturated, iso- and anteiso-methyl-branched
long-chain fatty acids (4). A. variabilis also differs from true
arthrobacters in possessing phosphatidylinositol diamannosides (Collins, unpublished data). A . variabilis has also
been shown to be unrelated to true arthrobacters on the basis
of 16s ribosomal RNA cataloging (10). These studies have
demonstrated that A . variabilis is more closely related to
true corynebacteria than to the other mycolic acidcontaining genera Mycobacterium, Nocardia, and
Rhodococcus (10). Therefore, in view of the overwhelming
phenotypic and phylogenetic evidence, it is formally proposed that A . variabilis be removed from the genus
Arthrobacter and reclassified in the genus Corynebacterium,
as Corynebacterium variabilis comb. nov.
Description of Corynebacteriurnvariabilis comb. nov. Grampositive, strictly aerobic, nonmotile, rod-shaped cells (0.8 to
1.1 by 1.4 to 3.5 pm). Cells are irregular (club-shaped or
tapered) and occur singly, in pairs with typical V forms or
clumps; ovoid forms occur in older cultures. Colonies are
small (ca. 2 to 4 mm), circular (sometimes irregular), convex,
and grey-white (occasionally slight pink) with a dry appearance. Optimum temperature is between 25 and 30°C. Grows
in 7% NaCl. Acetate, propionate, capronate, 4-aminobutyrate, caprylate, succinate, DL-malate, levulinate, and some
other compounds may be used as sole carbon sources (9).
Xanthine, tyrosine, and starch are not hydrolyzed. Catalase
positive, oxidase negative. Murein is of the directly crosslinked type based on rneso-diaminopimelic acid. The glycan
moiety of murein contains only acetyl residues. The cell wall
contains an arabinogalactan polymer. Short-chain mycolic
acids (30 to 36 carbon atoms) are present. Long-chain fatty
acids are of the straight-chain saturated, mono-unsaturated,
and 10-methyl-branchedtypes. The major menaquinones are
MK-9(H2) and MK-8(H2). The deoxyribonucleic acid base
composition is 65 mol% guanine plus cytosine (T,). The type
strain is ATCC 15753 (NCIB 9455). The characteristics of
the type strain correspond to those of the species.
Other distinguishing characteristics. Corynebacterium
variabilis can be readily distinguished from other
Corynebacterium species in containing high levels of 10methyloctadecanoic (tuberculostearic) acid. The only other
authentic Corynebacterium species known to contain this
acid is C. minutissirnum. C . variabilis, however, can be
readily distinguished from the latter species in being aerobic
and in possessing a substantially higher guanine-pluscytosine content (ca. 56 to 59 mol% for C. minutissimum)
(1).
LITERATURE CITED
1, Collins, M. D., and C. S. Cummins. 1986. Genus Corynebacterium Lehmann and Wuemann, p. 1266-1276. In P. H. A.
Sneath (ed.), Bergey’s manual of systematic bacteriology, vol.
2. The Williams and Wilkins Co., Baltimore.
2. Collins, M. D., M. Goodfellow, and D. E. Minnikin. 1982. A
survey of the structure of mycolic acids in Corynebacteriurn and
related taxa. J. Gen. Microbiol. 128:129-149.
3. Collins, M. D., M. Goodfellow, and D. E. Mhnikin. 1982. Fatty
acid composition of some mycolic acid-containing coryneform
bacteria. J. Gen. Microbiol. 128:2503-2509.
4. Collins, M. D., and R. M. Kroppenstedt. 1983. Lipid composition as a guide to the classification of some coryneform bacteria
containing an A4a type peptidoglycan (Schleifer and Kandler).
Syst. Appl. Microbiol. 4:95-104.
5. Keddie, R. M., M. D. Collins, and D. Jones. 1986. Genus
Arthrobacter Conn and Dimmick, p. 1288-1301. In P. H. A.
Sneath (ed.), Bergey’s manual of systematic bacteriology, vol.
2. The Williams and Wilkins Co., Baltimore.
6. Keddie, R. M., and G. L. Cure. 1977, The cell wall composition
and distribution of free mycolic acids in named strains of
coryneform bacteria and in isolates from various natural
sources. J. Appl. Bacteriol. 42:229-253.
7. Miiller, G. 1961. Mikrobiologische Untersuchungen iiber die
“Futterverpilzung durch Selbsterhitzung.” 111. Mitteilung:
Ausfuhrliche Beshreibung neuer Baktenen-species. Zentralbl.
287
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288
NOTES
INT. J. SYST.BACTERIOL.
Bakteriol. Parasitenkd. Infektionskr. Hyg. Abt. 2 Orig. Reihe A
114:52&537.
8. Schleifer, K. H., and 0. Kandler. 1972. Peptidoglycan types of
bacterial cell walls and their taxonomic implications. Bacteriol.
Rev. 35407477.
9. Seiler, H. 1983. Identification key for coryneform bacteria
derived from numerical taxonomic studies. J. Gen. Microbial.
129:1433-1471.
10. Stackebrandt, E., B. J. Lewis, and C. R. Wokse. 1980. The
phylogenetic structure of the coryneform group of bacteria.
Zentralbl. Bakteriol. Mikrobiol. Hyg. Abt. 2 Orig. Reihe C
1:137-149.
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