Summary auto-generated
Researchers conducted a comprehensive taxonomic study of nine yellow-pigmented bacterial strains isolated from diverse environments including a medieval wall painting, indoor air in a Venetian museum, and an activated-sludge plant in Australia. Using polyphasic taxonomy including 16S rRNA gene sequencing, DNA-DNA hybridization, chemotaxonomic analysis, and biochemical testing, all nine strains were confirmed to belong to Micrococcus luteus despite exhibiting significant differences from the type strain in chemotaxonomic features and physiological properties. DNA-DNA reassociation studies showed greater than 70% relatedness to M. luteus DSM 20030T. Notably, the isolates possessed MK-8(H2) as their major respiratory quinone and some displayed unusual peptidoglycan compositions. The researchers documented substantial intraspecific diversity in quinone systems, cell-wall peptidoglycan types, and biochemical properties. Rather than creating new species, they proposed dividing M. luteus into three distinct biovars based on these differences, recognizing the heterogeneity while maintaining nomenclatural stability. Emended descriptions of the genus Micrococcus and the species M. luteus and M. lylae were provided.
Key findings
- All nine isolates belonged to M. luteus species based on DNA-DNA hybridization (>70% relatedness), despite significant phenotypic differences from the type strain
- Three biovars of M. luteus were identified with distinct chemotaxonomic features: biovar I (type strain with MK-8/MK-8(H2) and A2 peptidoglycan), biovar II (eight novel strains with MK-8(H2) and A2 peptidoglycan), and biovar III (strain Ballarat with MK-8(H2) and rare A4α peptidoglycan)
- Novel isolates differed from M. luteus type strain in ability to assimilate maltose, trehalose, 3-hydroxybutyrate, lactate, pyruvate, and histidine, and to hydrolyze casein
- Strain Ballarat exhibited an unusual A4α peptidoglycan type previously found only in Arthrobacter woluwensis, representing the first report in M. luteus
- FT-IR spectroscopy analysis clearly grouped the eight novel isolates separately from the type strains, supporting the proposed biovar classifications
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Abstract
M. Wieser, EBM. Denner, P. Kampfer, P. Schumann, B. Tindall, U. Steiner, D. Vybiral, W. Lubitz, A. M. Maszenan, BKC. Patel, R. J. Seviour, C. Radax and H. J. Busse
Institut fur Mikrobiologie und Genetik, Universitat Wien, A-1030 Wien, Austria
Nine yellow-pigmented, spherical bacterial strains isolated from a medieval wall painting (strain D7), from indoor air (strains 3, 6, 7, 13C2, 38, 83 and 118) and from an activated-sludge plant (strain Ballarat) were classified by a polyphasic approach. Analyses of the 16S rRNA gene sequences of three representatives (strains D7, 118 and Ballarat) indicated that they all belong to the genus Micrococcus. The three isolates shared the highest sequence similarities with Micrococcus luteus DSM 20030(T) (97.9--98%), Micrococcus antarcticus AS 1.2372(T) (97.9--98.3%) and Micrococcus lylae DSM 20315(T) (97.5--97.9%). DNA--DNA reassociation studies clearly demonstrated that all nine isolates belong to the species M. luteus. However, neither their chemotaxonomic features nor their physiological and biochemical properties were consistent with those of M. luteus DSM 20030(T). In contrast to M. luteus DSM 20030(T), all isolates investigated possessed MK-8(H(2)) as the major respiratory quinone, and strain Ballarat had an A4alpha peptidoglycan type. On the basis of analyses of their Fourier transform-infrared spectroscopy spectra, isolates D7, 3, 6, 7, 13C2, 38, 83 and 118 could be grouped into a single cluster separate from M. luteus DSM 20030(T), strain Ballarat and M. lylae DSM 20315(T). In addition, all these isolates could be distinguished from M. luteus DSM 20030(T) by their ability to assimilate D-maltose, D-trehalose, DL-3-hydroxybutyrate, DL-lactate, pyruvate and L-histidine and to hydrolyse casein. Strains D7, 3, 6, 7, 13C2, 38, 83 and 118 differed from both M. luteus DSM 20030(T) and strain Ballarat by their ability to assimilate acetate, L-phenylalanine, L-serine and phenylacetate. Furthermore, REP-PCR fingerprinting yielded one common band for these strains, whereas this band was not observed for M. luteus DSM 20030(T), strain Ballarat or M. lylae DSM 20315(T). On the basis of these data, the species M. luteus can be divided into three biovars that are distinguished by several chemotaxonomic and biochemical traits: biovar I, represented by M. luteus DSM 20030(T); biovar II, represented by strains D7 (=DSM 14234=CCM 4959), 3, 6, 7, 13C2, 38, 83 and 118; and biovar III, represented by strain Ballarat (=DSM 14235=CCM 4960). On the basis of the results generated in this study, emended descriptions of the genus Micrococcus and the species M. luteus and M. lylae are given.