Suprageneric classification of peptidoglycan group B actinomycetes by nucleotide sequencing of 5S ribosomal RNA

Haloactinobacterium album gen. nov., sp. nov., a halophilic actinobacterium, and proposal of Ruaniaceae fam. nov

A Gram-staining-positive, facultatively anaerobic, non-motile and moderately halophilic actinobacterium, designated YIM 93306T, was isolated from a salt lake in Xinjiang province, north-west China, and subjected to a polyphasic taxonomic study. Strain YIM 93306T grew in the presence of 2–16 % (w/v) NaCl and did not grow without NaCl. The peptidoglycan type was A4α with an l-Lys–l-Glu interpeptide bridge. The whole-cell sugars were glucosamine, arabinose, mannose and two unknown sugars. The predominant menaquinone was MK-8(H4). The major fatty acids were iso-C15 : 0, anteiso-C15 : 0 and anteiso-C17 : 0. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, one unknown phosphoglycolipid and one unknown phospholipid. The DNA G+C content was 68.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain YIM 93306T fell within the radius of the suborder Micrococcineae. Its closest phylogenetic neighbour was the type strain of Ruania albidiflava (AS 4.3142T; 96.2 % 16S rRNA gene sequence similarity), the sole recognized species of the genus Ruania. Sequence similarities between strain YIM 93306T and members of other genera of the suborder Micrococcineae were <95.2 %. On the basis of phylogenetic analysis, phenotypic characteristics and chemotaxonomic differences, a novel genus and species, Haloactinobacterium album gen. nov., sp. nov., is proposed. The type strain of the species is YIM 93306T (=DSM 21368T =KCTC 19413T =CCTCC AB 208069T). Based on phylogenetic characteristics and 16S rRNA gene signature nucleotide patterns, the genera Ruania and Haloactinobacterium gen. nov. are proposed to belong to a novel family, Ruaniaceae fam. nov.

Agrococcus carbonis sp. nov., isolated from soil of a coal mine

An actinobacterial strain, designated G4(T), isolated from a coal mine was subjected to polyphasic taxonomic characterization. Cells were Gram-stain-positive, yellow-pigmented, non-motile and non-spore-forming cocci. This organism possessed a type B peptidoglycan with diaminobutyric acid as diagnostic diamino acid. The major respiratory quinones were MK-9, MK-10 and MK-11. The major fatty acids were anteiso-C(15 : 0) (41.6 %) and anteiso-C(17 : 0) (32.8 %). The predominant cellular polar lipids were diphosphatidylglycerol and phosphatidylglycerol. Cell wall sugars comprised galactose, glucose, ribose and rhamnose. 16S rRNA gene sequence analysis of strain G4(T) showed high similarity with Agrococcus baldri (98.9 %), Agrococcus citreus (97.8 %), Agrococcus jenensis (97.3 %) and Agrococcus terreus (97.0 %). Sequence similarity with the type strains of the other species of the genus Agrococcus was less than 97.0 %. The DNA-DNA relatedness of strain G4(T) with the type strains of Agrococcus baldri, Agrococcus citreus, Agrococcus jenensis and Agrococcus terreus was less than 70 %. On the basis of the physiological, biochemical and chemotaxonomic characteristics, strain G4(T) should be classified as the type strain of a novel species of the genus Agrococcus, for which the name Agrococcus carbonis sp. nov. is proposed. The type strain is G4(T) ( = MTCC 10213(T)  = DSM 22965(T)).

Pseudoclavibacter chungangensis sp. nov., isolated from activated sludge

The taxonomic position of a Gram-positive, non-spore-forming strain, designated CAU 59T, from activated sludge was investigated. Colony morphology, biochemical tests and chemotaxonomic investigations revealed that strain CAU 59T possessed the characteristics of the genus Pseudoclavibacter. Comparative 16S rRNA gene sequence analysis showed sequence divergence values between strain CAU 59T and other described Pseudoclavibacter species of more than 3.6 %, and the strain formed a hitherto-unknown subline within the genus Pseudoclavibacter. DNA–DNA hybridization studies showed that strain CAU 59T displayed 20.9 % relatedness to its closest phylogenetic neighbour, Pseudoclavibacter helvolus DSM 20419T. The DNA G+C content was 66.2 mol%. The phenotypic, chemotaxonomic and genotypic data indicated that strain CAU 59T represents a novel species of the genus Pseudoclavibacter, for which the name Pseudoclavibacter chungangensis sp. nov. is proposed. The type strain is CAU 59T (=KCTC 22691T =CCUG 58142T).

The endolysins of bacteriophages CMP1 and CN77 are specific for the lysis of Clavibacter michiganensis strains

Putative endolysin genes of bacteriophages CMP1 and CN77, which infect Clavibacter michiganensis subsp. michiganensis and C. michiganensis subsp. nebraskensis, respectively, were cloned and expressed in Escherichia coli. The His-tagged endolysin of CMP1 consists of 306 amino acids and has a calculated molecular mass of 34.8 kDa, while the His-tagged endolysin of CN77 has 290 amino acids with a molecular mass of 31.9 kDa. The proteins were purified and their bacteriolytic activity was demonstrated. The bacteriolytic activity of both enzymes showed a host range which was limited to the respective C. michiganensis subspecies and did not affect other bacteria, even those closely related to Clavibacter. Due to the high specificity of the CMP1 and CN77 endolysins they may be useful tools for biocontrol of plant-pathogenic C. michiganensis without affecting other bacteria in the soil.

Chryseoglobus frigidaquae gen. nov., sp. nov., a novel member of the family Microbacteriaceae

A motile, rod-shaped, yellow-pigmented bacterium, designated strain CW1(T), was isolated from a water-cooling system in the Republic of Korea. Cells were Gram-stain-positive, aerobic, catalase-positive and oxidase-negative. Strain CW1(T) formed slender rods with unusual bulbous protuberances. The major fatty acids were iso-C(16 : 1) (33.7 %), anteiso-C(15 : 0) (27.2 %), iso-C(14 : 0) (13.3 %) and C(16 : 0) (10.8 %). The cell-wall peptidoglycan was of type B2beta, containing lysine as the diamino acid. The respiratory quinones were menaquinones with 12, 13 and 14 isoprene units. A phylogenetic tree based on 16S rRNA gene sequences showed that strain CW1(T) formed an evolutionary lineage within the radiation enclosing members of the family Microbacteriaceae and was related to, but distant from, members of the genera Microcella and Yonghaparkia. On the basis of the evidence presented, strain CW1(T) is considered to represent a novel species of a new genus in the family Microbacteriaceae, for which the name Chryseoglobus frigidaquae gen. nov., sp. nov. is proposed. The type strain of Chryseoglobus frigidaquae is CW1(T) (=KCTC 13142(T) =JCM 14730(T)).

An update of the structure and 16S rRNA gene sequence-based definition of higher ranks of the class Actinobacteria, with the proposal of two new suborders and four new families and emended descriptions of the existing higher taxa

The higher ranks of the class Actinobacteria were proposed and described in 1997. At each rank, the taxa were delineated from each other solely on the basis of 16S rRNA gene sequence phylogenetic clustering and taxon-specific 16S rRNA signature nucleotides. In the past 10 years, many novel members have been assigned to this class while, at the same time, some members have been reclassified. The new 16S rRNA gene sequence information and the changes in phylogenetic positions of some taxa influence decisions about which 16S rRNA nucleotides to define as taxon-specific. As a consequence, the phylogenetic relationships of Actinobacteria at higher levels may need to be reconstructed. Here, we present new 16S rRNA signature nucleotide patterns of taxa above the family level and indicate the affiliation of genera to families. These sets replace the signatures published in 1997. In addition, Actinopolysporineae subord. nov. and Actinopolysporaceae fam. nov. are proposed to accommodate the genus Actinopolyspora, Kineosporiineae subord. nov. and Kineosporiaceae fam. nov. are proposed to accommodate the genera Kineococcus, Kineosporia and Quadrisphaera, Beutenbergiaceae fam. nov. is proposed to accommodate the genera Beutenbergia, Georgenia and Salana and Cryptosporangiaceae fam. nov. is proposed to accommodate the genus Cryptosporangium. The families Nocardiaceae and Gordoniaceae are proposed to be combined in an emended family Nocardiaceae. Emended descriptions are also proposed for most of the other higher taxa.

Salinibacterium xinjiangense sp. nov., a psychrophilic bacterium isolated from the China No. 1 glacier

A novel psychrophilic, Gram-positive, yellow-pigmented and aerobic bacterium, strain 0543(T), was isolated from the China No. 1 glacier. Strain 0543(T) was able to grow at 4-23 degrees C, with optimum growth at 18-19 degrees C. The major fatty acids were anteiso-C(15 : 0) (58.36 %), iso-C(16 : 0) (21.13 %), iso-C(14 : 0) (10.25 %) and anteiso-C(17 : 0) (7.16 %). The genomic DNA G+C content was 63.5 mol% and the major menaquinone was MK-10. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 0543(T) represented a lineage within the family Microbacteriaceae, with the highest similarity of 97.4 % with Salinibacterium amurskyense KMM 3673(T). On the basis of polyphasic, chemotaxonomic, physiological and biochemical evidence from this study, the novel species Salinibacterium xinjiangense sp. nov. is proposed; the type strain is 0543(T)(=CGMCC 1.5381(T) =JCM 13926(T)).

Curtobacterium ginsengisoli sp. nov., isolated from soil of a ginseng field

A Gram-positive, non-motile, pale-yellow, short rod-shaped bacterium, strain DCY26(T), was isolated from soil of a ginseng field in South Korea and was investigated to determine its taxonomic position. The organism grew optimally at 30-37 degrees C. The G+C content of its DNA was 65.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain DCY26(T) was related most closely to species of the genus Curtobacterium, in the family Microbacteriaceae. Strain DCY26(T) showed highest 16S rRNA gene sequence similarity to Curtobacterium pusillum DSM 20527(T) (96.3 %), Curtobacterium luteum DSM 20542(T) (96.2 %), Curtobacterium flaccumfaciens LMG 3645(T) (96.2 %), Curtobacterium citreum DSM 20528(T) (96.1 %), Curtobacterium albidum DSM 20512(T) (96.1 %) and Curtobacterium herbarum DSM 14013(T) (95.3 %). The predominant menaquinone of strain DCY26(T) was MK-9. Other chemotaxonomic data also supported the affiliation of strain DCY26(T) to the genus Curtobacterium. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain DCY26(T) is considered to represent a novel species of the genus Curtobacterium, for which the name Curtobacterium ginsengisoli sp. nov. is proposed. The type strain is DCY26(T) (=KCTC 13163(T) =JCM 14773(T)).

Genome of the actinomycete plant pathogen Clavibacter michiganensis subsp. sepedonicus suggests recent niche adaptation

Clavibacter michiganensis subsp. sepedonicus is a plant-pathogenic bacterium and the causative agent of bacterial ring rot, a devastating agricultural disease under strict quarantine control and zero tolerance in the seed potato industry. This organism appears to be largely restricted to an endophytic lifestyle, proliferating within plant tissues and unable to persist in the absence of plant material. Analysis of the genome sequence of C. michiganensis subsp. sepedonicus and comparison with the genome sequences of related plant pathogens revealed a dramatic recent evolutionary history. The genome contains 106 insertion sequence elements, which appear to have been active in extensive rearrangement of the chromosome compared to that of Clavibacter michiganensis subsp. michiganensis. There are 110 pseudogenes with overrepresentation in functions associated with carbohydrate metabolism, transcriptional regulation, and pathogenicity. Genome comparisons also indicated that there is substantial gene content diversity within the species, probably due to differential gene acquisition and loss. These genomic features and evolutionary dating suggest that there was recent adaptation for life in a restricted niche where nutrient diversity and perhaps competition are low, correlated with a reduced ability to exploit previously occupied complex niches outside the plant. Toleration of factors such as multiplication and integration of insertion sequence elements, genome rearrangements, and functional disruption of many genes and operons seems to indicate that there has been general relaxation of selective pressure on a large proportion of the genome.

The genome sequence of the tomato-pathogenic actinomycete Clavibacter michiganensis subsp. michiganensis NCPPB382 reveals a large island involved in pathogenicity

Clavibacter michiganensis subsp. michiganensis is a plant-pathogenic actinomycete that causes bacterial wilt and canker of tomato. The nucleotide sequence of the genome of strain NCPPB382 was determined. The chromosome is circular, consists of 3.298 Mb, and has a high G+C content (72.6%). Annotation revealed 3,080 putative protein-encoding sequences; only 26 pseudogenes were detected. Two rrn operons, 45 tRNAs, and three small stable RNA genes were found. The two circular plasmids, pCM1 (27.4 kbp) and pCM2 (70.0 kbp), which carry pathogenicity genes and thus are essential for virulence, have lower G+C contents (66.5 and 67.6%, respectively). In contrast to the genome of the closely related organism Clavibacter michiganensis subsp. sepedonicus, the genome of C. michiganensis subsp. michiganensis lacks complete insertion elements and transposons. The 129-kb chp/tomA region with a low G+C content near the chromosomal origin of replication was shown to be necessary for pathogenicity. This region contains numerous genes encoding proteins involved in uptake and metabolism of sugars and several serine proteases. There is evidence that single genes located in this region, especially genes encoding serine proteases, are required for efficient colonization of the host. Although C. michiganensis subsp. michiganensis grows mainly in the xylem of tomato plants, no evidence for pronounced genome reduction was found. C. michiganensis subsp. michiganensis seems to have as many transporters and regulators as typical soil-inhabiting bacteria. However, the apparent lack of a sulfate reduction pathway, which makes C. michiganensis subsp. michiganensis dependent on reduced sulfur compounds for growth, is probably the reason for the poor survival of C. michiganensis subsp. michiganensis in soil.

Yonghaparkia alkaliphila gen. nov., sp. nov., a novel member of the family Microbacteriaceae isolated from an alkaline soil

Two Gram-positive, non-motile, non-spore-forming and rod-shaped actinomycete strains, KSL-113T and KSL-133, were isolated from an alkaline soil in Korea, and their taxonomic positions were investigated by using a polyphasic approach. The strains grew optimally at 30 °C and pH 9.0. Phenotypic, phylogenetic and genetic similarities indicated that strains KSL-113T and KSL-133 represent the same species. Phylogenetic analyses based on 16S rRNA gene sequences showed that strains KSL-113T and KSL-133 fell within the family Microbacteriaceae of the suborder Micrococcineae, the highest 16S rRNA gene sequence similarity values (98.2 %) being obtained with respect to Microcella putealis CV-2T. The 16S rRNA gene sequence similarities between strains KSL-113T and KSL-133 and the other members of the family Microbacteriaceae used in the phylogenetic analysis were less than 96.0 %. Strains KSL-113T and KSL-133 could be clearly distinguished from members of the family Microbacteriaceae on the basis of differences in chemotaxonomic properties, including the predominant menaquinone type, the cell-wall peptidoglycan type and the fatty acid profile. Accordingly, on the basis of the combined phenotypic, chemotaxonomic and phylogenetic data, strains KSL-113T and KSL-133 constitute a novel genus and species of the family Microbacteriaceae, for which the name Yonghaparkia alkaliphila gen. nov., sp. nov. is proposed. The type strain of Yonghaparkia alkaliphila is KSL-113T (=KCTC 19126T=CIP 108920T).

Agrococcus lahaulensis sp. nov., isolated from a cold desert of the Indian Himalayas

The taxonomic position of a lemon-yellow-pigmented actinobacterium, strain K22-21T, isolated from a soil sample from Lahaul-Spiti Valley in the Indian Himalayas, was determined using a polyphasic approach. The strain had phenotypic and chemical properties that were consistent with its classification in the genusAgrococcus. Alignment of the 16S rRNA gene sequence of strain K22-21Twith sequences fromAgrococcus jenensisDSM 9580T,Agrococcus baldriDSM 14215TandAgrococcus citreusDSM 12453Trevealed similarities of 98.5, 96.8 and 96.6 %, respectively. However, the level of DNA–DNA relatedness between strain K22-21TandA. jenensiswas 55.1 %. The novel strain could be distinguished from type strains of the three species of the genusAgrococcususing DNA–DNA relatedness and phenotypic data. Based on these differences, strain K22-21T(=MTCC 7154T=DSM 17612T) should be classified as the type strain of a novel species ofAgrococcus, for which the nameAgrococcus lahaulensissp. nov. is proposed.

Microcella putealis gen. nov., sp. nov., a Gram-positive alkaliphilic bacterium isolated from a nonsaline alkaline groundwater

Three Gram-positive bacteria designated CV-2T, CV-40 and AC-30 were isolated from a highly alkaline groundwater environment (pH 11.4). These organisms formed very small rod-shaped cells, are aerobic, non-spore-forming, catalase-positive, oxidase-negative, with an optimum growth temperature of 35 degrees C and optimum pH value of growth between 8.5 and 9.0. The strains possessed a novel B-type cell-wall peptidoglycan structure with lysine as the diamino acid; the major respiratory quinones were menaquinone 12 (MK12) and MK13. The G + C content of DNA was between 67.1 and 70.7 mol%. The phylogenetic analyses of the sequences of the 16S rRNA genes reveled that they formed a deep branch within the family Microbacteriaceae, with the highest similarity of approximately 95.6% with members of the genera Agreia, Agrococcus, Cryobacterium, Clavibacter, Frigoribacterium, Leifsonia, Mycetocola, Rhodoglobus, Salinibacterium and Subtercola. Based on the phylogenetic analyses and distinct phenotypic characteristics, we are of the opinion that strains CV-2T, CV-40 and AC-30, represent a new species of a novel genus within the family Microbacteriaceae for which we propose the name Microcella putealis gen. nov., sp. nov.

Zimmermannella helvola gen. nov., sp. nov., Zimmermannella alba sp. nov., Zimmermannella bifida sp. nov., Zimmermannella faecalis sp. nov. and Leucobacter albus sp. nov., novel members of the family Microbacteriaceae

Seven strains of actinobacteria, isolated from soil, wounds, urine, cow faeces, human blood and butter, were characterized by a polyphasic approach to clarify their taxonomic position. On the basis of chemotaxonomy, 16S rRNA gene analysis and DNA relatedness, strain IAM 14851T can be classified within the cluster of the genus Leucobacter and is proposed as a novel species, Leucobacter albus sp. nov., with strain IAM 14851T (=TISTR 1515T) as the type strain. The other six strains formed a phylogenetically separate branch in the family Microbacteriaceae, having the following characteristics: the major menaquinones are MK-8 to MK-10, the DNA G + C content ranges from 62 to 68 mol%, the diamino acid in the cell wall is diaminobutyric acid and the muramic acid in the peptidoglycan is of the acetyl type. The major fatty acids are 12-methyltetradecanoic acid (anteiso-C(15 : 0)), hexadecanoic acid (C(16 : 0)), 14-methyl-pentadecanoic acid (iso-C(16 : 0)) and 14-methyl-hexadecanoic acid (anteiso-C(17 : 0)). On the basis of morphological, physiological and chemotaxonomic characteristics, together with DNA-DNA hybridization and 16S rRNA gene sequence comparison, the novel genus Zimmermannella gen. nov. is proposed for these six strains. Four novel species are proposed: Zimmermannella helvola sp. nov. (type species; type strain IAM 14726T = NBRC 15775T = DSM 20419T = TISTR 1509T), Zimmermannella alba sp. nov. (type strain IAM 14724T = NBRC 15616T = TISTR 1510T), Zimmermannella bifida sp. nov. (type strain IAM 14848T = TISTR 1511T) and Zimmermannella faecalis sp. nov. (type strain IAM 15030T = NBRC 15706T = ATCC 13722T = TISTR 1514T).

Development of PCR primers specific for the amplification and direct sequencing of gyrB genes from microbacteria, order Actinomycetales

PCR primer sets were developed for the specific amplification and sequence analyses encoding the gyrase subunit B (gyrB) of members of the family Microbacteriaceae, class Actinobacteria. The family contains species highly related by 16S rRNA gene sequence analyses. In order to test if the gene sequence analysis of gyrB is appropriate to discriminate between closely related species, we evaluate the 16S rRNA gene phylogeny of its members. As the published universal primer set for gyrB failed to amplify the responding gene of the majority of the 80 type strains of the family, three new primer sets were identified that generated fragments with a composite sequence length of about 900 nt. However, the amplification of all three fragments was successful only in 25% of the 80 type strains. In this study, the substitution frequencies in genes encoding gyrase and 16S rDNA were compared for 10 strains of nine genera. The frequency of gyrB nucleotide substitution is significantly higher than that of the 16S rDNA, and no linear correlation exists between the similarities of both molecules among members of the Microbacteriaceae. The phylogenetic analyses using the gyrB sequences provide higher resolution than using 16S rDNA sequences and seem able to discriminate between closely related species.

Isolation and characterization of efficient isoxaben-transforming Microbacterium sp strains from four European soils

Nutrient-agar plates containing isoxaben (500 mg litre(-1)) were used to isolate isoxaben-metabolising bacteria from four European soils incubated with the herbicide under laboratory conditions. In flask experiments, inoculation of a basal salts medium containing nitrogen and [phenyl-U-14C]isoxaben with an isolate (B2b) resulted in 33% recovery of the initial radioactivity as [14C]carbon dioxide after 2 weeks. A major metabolite identified by GC-MS and NMR analysis as 3-(1-ethyl-1-methylpropyl)isoxazol-5-ylamine accumulated both in basal salts and nutrient broth media. 2,6-Dimethoxybenzoic acid, a suspected metabolite of isoxaben, was not detected in either liquid media. However, the capability of the B2b isolate to use 2,6-dimethoxybenzoic acid as a source of carbon was demonstrated. Soil inoculation with the B2b strain resulted in an increase in the recovery of [14C] carbon dioxide from both [phenyl-U-14C] and [isoxazole-5-14C]isoxaben. The metabolite identified as 3-(1-ethyl-1-methylpropyl)isoxazole-5-ylamine only accumulated if the soil was autoclaved before inoculation. This metabolite was rapidly mineralized by the microflora of a natural soil without history of isoxaben treatment. Homology patterns of sequenced 16S rDNA between isoxaben-transforming isolates and reference strains showed that the four isolates identified belonged to the genus Microbacterium.

Clinical microbiology of coryneform bacteria

Coryneform bacteria are aerobically growing, asporogenous, non-partially-acid-fast, gram-positive rods of irregular morphology. Within the last few years, there has been a massive increase in the number of publications related to all aspects of their clinical microbiology. Clinical microbiologists are often confronted with making identifications within this heterogeneous group as well as with considerations of the clinical significance of such isolates. This review provides comprehensive information on the identification of coryneform bacteria and outlines recent changes in taxonomy. The following genera are covered: Corynebacterium, Turicella, Arthrobacter, Brevibacterium, Dermabacter. Propionibacterium, Rothia, Exiguobacterium, Oerskovia, Cellulomonas, Sanguibacter, Microbacterium, Aureobacterium, "Corynebacterium aquaticum," Arcanobacterium, and Actinomyces. Case reports claiming disease associations of coryneform bacteria are critically reviewed. Minimal microbiological requirements for publications on disease associations of coryneform bacteria are proposed.