Nocardia iowensis sp. nov., an organism rich in biocatalytically important enzymes and nitric oxide synthase

Abstract

Nocardia strain NRRL 5646, isolated from a garden soil sample in Osceola, Iowa, USA, was initially of interest as an antibiotic producer. It contained biocatalytically important enzymes and represented the first described nitric oxide synthase enzyme system in bacteria. The present polyphasic taxonomic study was undertaken to differentiate strain NRRL 5646(T) from related species of the genus Nocardia. Chemotaxonomic analyses included determinations of the fatty acid methyl ester profile (C(16 : 1)omega6c/C(16 : 1)omega7c, C(16 : 0), C(18 : 1)omega9c and C(18 : 0) 10-methyl as major components), quinone [cyclo MK-8(H(4)) as the major component], polar lipid (diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside as major components) and mycolic acid. These results supported its placement within the genus Nocardia. Biochemical testing and 16S rRNA, 65-kDa heat-shock protein (hsp65) and preprotein translocase (secA1) gene sequence analyses differentiated strain NRRL 5646(T) from recognized Nocardia species. Previous studies have demonstrated that other genetic sequences (carboxylic acid reductase, Nocardia phosphopantetheinyl transferase and GTP cyclohydrolase I) from strain NRRL 5646(T) can also be used to substantiate its uniqueness. The level of 16S rRNA gene sequence similarity between strain NRRL 5646(T) and the type strains of Nocardia tenerifensis and Nocardia brasiliensis was 98.8 %. However, strain NRRL 5646(T) could be clearly distinguished from these Nocardia species based on DNA-DNA hybridization data. Consequently, strain NRRL 5646(T) is considered to represent a novel species of the genus Nocardia, for which the name Nocardia iowensis sp. nov. is proposed. The type strain is NRRL 5646(T) (=UI 122540(T)=NRRL B-24671(T)=DSM 45197(T)).

Fig. 1.

Unrooted neighbour-joining tree (Saitou & Nei, 1987), based on nearly complete 16S rRNA gene sequences, showing the position of strain NRRL 5646^T among representatives of closely related Nocardia species. Phylogenetic data were recovered by using the maximum-likelihood (Felsenstein, 1981) and maximum-parsimony (Kluge & Farris, 1969) tree-making algorithms, respectively. Numbers at nodes indicate levels of bootstrap support based on a neighbour-joining analysis of 1000 resampled datasets; only values >50 % are given. Asterisks indicate branches that were also found in trees constructed based on hsp65 and secAI gene sequences (see Figs 2 and 3). Bar, 0.01 changes per nucleotide position.

Fig. 2.

Unrooted neighbour-joining tree (Saitou & Nei, 1987), based on complete hsp65 gene sequences, showing the position of strain NRRL 5646^T among representatives of closely related Nocardia species. Phylogenetic data were recovered by using the maximum-likelihood (Felsenstein, 1981) and maximum-parsimony (Kluge & Farris, 1969) tree-making algorithms, respectively. Numbers at nodes indicate levels of bootstrap support based on a neighbour-joining analysis of 1000 resampled datasets; only values >50 % are given. Asterisks indicate branches that were also found in trees constructed based on 16S rRNA and secAI gene sequences (see Figs 1 and 3). Bar, 0.01 changes per nucleotide position.

Fig. 3.

Unrooted neighbour-joining tree (Saitou & Nei, 1987), based on complete secA1 gene sequences, showing the position of strain NRRL 5646^T among representatives of closely related Nocardia species. Phylogenetic data were recovered by using the maximum-likelihood (Felsenstein, 1981) and maximum-parsimony (Kluge & Farris, 1969) tree-making algorithms, respectively. Numbers at nodes indicate levels of bootstrap support based on a neighbour-joining analysis of 1000 resampled datasets; only values >50 % are given. Asterisks indicate branches that were also found in trees constructed based on 16S rRNA and hsp65 gene sequences (see Figs 1 and 2). Bar, 0.01 changes per nucleotide position.