Taxonomic Study of Paracoccus denitrificans

Abstract

Isolates of Paracoccus denitrijicans were obtained from various habitats by enrichment in a mineral medium, using molecular hydrogen as the hydrogen donor and nitrate as the hydrogen acceptor. A total of 11 strains were compared with the following three reference strains: P . denitrijcans Stanier 381T (type strain) (= DSM 65T = ATCC 17741T), Morris (= DSM 413 = ATCC 19367), and Vogt (= DSM 415). A computer analysis based on 235 characters indicated that the strains clustered into subgroups. Deoxyribonucleic acid-deoxyribonucleic acid homology determinations confirmed this suggestion. A formal description of the species is presented, and the taxonomic position of P . denitrijcans is discussed. Paracoccus denitrijicans (formerly known asMicrococcus denitriJicans) was first isolated by Beijerinck and Minkman ( 5 ) and was reisolated as a bacterium that was capable of using molecular hydrogen in denitrification by Verhoeven et al. (56) and Vogt (57). Although this species has a guanine-plus-cytosine (G + C) content similar to the G+C contents of some members of Micrococcus, it differs from other species of Micrococcus as follows (40): (i) P. denitr$cans forms rod-shaped cells in young cultures (34, 39, 55, 57); (ii) it is gram negative (9, 34, 56, 57); (iii) it has a cell wall peptidoglycan which contains a wide range of amino acids characteristic of gram-negative genera, and the cell wall contains diaminopimelic acid in place of the lysine characteristic of micrococci (4); and (iv) it contains ubiquinone as an electron carrier (46), which is characteristic of gram-negative bacteria. For these reasons a new genus, Paracoccus was created (9). The electron transport chain of P . denitrifcans resembles the electron transport chain of the inner mitochondria1 membrane more closely than the electron transport chain of any other bacterium (21). The hydrogenase of P . denitrifcans strain Stanier 381T (type strain) has been isolated and characterized (49, 50), and the regulation of hydrogenase formation as a diagnostic character of the reference strains of P . denitrijicans and of newly isolated strains has been studied (35).Although P. denitr8can.s was isolated more than 70 years ago (5) and has been used in many investigations, its taxonomic position is still ill defined; the genus was placed with "genera of uncertain affiliation" (11) because only two strains were available for study and taxonomic data were lacking.The objectives of this study were to isolate many new strains of P . denitrijicans, to determine their main features, to compare them with the strains kept in culture collections, to evaluate their similarities and delineate them from other related bacteria, and to determine their taxonomic niche.

Integration of heterologous DNA into the genome of Paracoccus denitrificans is mediated by a family of IS1248-related elements and a second type of integrative recombination event

“…This finding is in agreement with taxonomic studies that showed that DSM413 and DSM415 are closely related and that DSM65 T is a rather distinct member of the Paracoccus genus (17). An interesting result came from a comparison of the fingerprints of DSM413 and NCIB8944.…”

Mucilaginibacter roseus sp. nov., isolated from a freshwater river

“…The effect of antibiotics on cell growth was assessed after 3 days at 25 8C. A strain was considered susceptible when the diameter of the inhibition zone was .13 mm, intermediate at 10-12 mm and resistant at ,10 mm as described by Nokhal & Schlegel (1983).…”

Lacimicrobium alkaliphilum gen. nov., sp. nov., a member of the family Alteromonadaceae isolated from a salt lake

“…Susceptibility to antibiotics was determined by the disc diffusion method using filter-paper discs (Beijing Pharmaceutical Company), which contained various antibiotics as specified below. Growth inhibition effects were observed and estimated according to Nokhal & Schlegel (1983) after incubation on MA (pH 7.5) for 2 days at 30 8C. The inhibition zones were measured from the edges of susceptibility disks to the edges of the clear zones.…”