V. N. Akimov

Rathayibacter gen, nov., Including the Species Rathayibacter rathayi comb , nov,, Rathayibacter tritici comb , nov,, Rathayibacter iranicus comb, nov., and Six Strains from Annual Grasses

A new genus, Rathayibacter, is proposed to accommodate three species of gram-positive, aerobic, coryneform bacteria previously placed in the genus Clavibacter (Rathayibacter rathayi comb. nov., Rathayibacter tritici comb. nov., and Rathayibacter iranicus comb. nov.), as well as six strains that were isolated from annual cereal grasses, may be responsible for ryegrass toxicity, and are very similar to the recently described organism Clavibacter toxicus sp. nov. (I. T. Riley and K. M. Ophel, Int. J. Syst. Bacteriol. 42:64-68, 1992). The properties of members of the genus Rathayibacter include coryneform morphology, peptidoglycan based on 2,4-diaminobutyric acid (type B2γ), predominant menaquinones of the MK-10 type, and phosphatidylglycerol and diphosphatidylglycerol as basic polar lipids. The DNA base compositions range from 63 to 72 mol% G+C. The members of the new genus form a phenetic cluster distinct from Clavibacter spp. at a level of 71% (simple matching coefficient) and exhibit 7 to 9% DNA-DNA reassociation with strains of Clavibacter spp. In contrast to Clavibacter spp., most Rathayibacter strains are associated with nematodes belonging to the genus Anguina. The Rathayibacter species differ from species belonging to related genera (e.g., Clavibacter and Agromyces species) in the following characteristics: Menaquinone and whole-cell sugar compositions, results of lysozyme-sodium dodecyl sulfate test (which indicates differences in cell wall composition), ability to utilize a number carbon sources, resistance to bacteriocins of some Clavibacter spp., and other characteristics. The Rathayibacter species can be differentiated from each other by following characteristics: Presence or absence of xylose and galactose in the cell walls, fatty acid composition, ability to assimilate various sources of carbon and nitrogen, hydrolytic activity, tolerance to 5% NaCI and 0.03% potassium tellurite, susceptibility to iranicin, and absence or presence of plasmids of certain sizes. The type species of the genus Rathayibacter is R. rathayi. The type strains of the species are R. rathayi VKM Ac-1601 (= ICMP 2574), R. iranicus VKM Ac-1602 (= ICMP 3496), and R. tritici VKM Ac-1603 (= ICMP 2626).

Polyamine distribution in Actinomycetes with group B peptidoglycan and species of the genera Brevibacterium, Corynebacterium, and Tsukamurella

Polyamine patterns of 75 strains of actinobacteria belonging to the genera Agrococcus, Agromyces, Aureobacterium, Brevibacterium, Clavibacter, Corynebacterium, Curtobacterium, Microbacterium, Rathayibacter, and Tsukamurella were analyzed in order to investigate the suitability of this approach for differentiation within this group. The results revealed that the overall polyamine contents differ significantly among genera and that various patterns are present in actinobacteria. One characteristic pattern found in the genera Clavibacter, Rathayibacter, and Curtobacterium included a high polyamine concentration, and the polyamines were mainly spermidine and spermine. This feature distinguished the 2,4-diaminobuturic acid-containing genera Rathayibacter, Clavibacter, and Agromyces, which contained low concentrations of polyamines. Strains of the genus Brevibacterium were characterized by the presence of high concentrations of cadavarine and usually high concentrations of putrescine. Members of the genus Corynebacterium had relatively low polyamine contents, and usually spermidine was the major polyamine. A similar polyamine pattern was detected in the species of the genus Tsukamurella. No homogeneous polyamine patterns were detected in representatives of the genera Microbacterium and Aureobacterium, which are phylogenetically intermixed (M. Takeuchi and A. Yokota, FEMS Microbiol. Lett. 124:11–16, 1994). The results of polyamine analyses are in good agreement with the genetic heterogeneity within the actinobacteria and demonstrate that polyamine patterns are suitable for use in classification of actinobacterial taxa.

Halo-and psychrotolerant Geomyces fungi from arctic cryopegs and marine deposits

Comparative characterization of Geomyces isolates was performed. The isolates were obtained from Arctic cryopegs and the surrounding ancient marine deposits, from nonsaline permafrost soils, and from temperate environments. Microbiological (cultural and morphological) and molecular criteria were used to confirm the identification of the isolates as Geomyces pannorum. The isolates from cryopegs and surrounding marine deposits were shown to differ from those obtained from nonsaline soils and temperate environments in their ability to grow at negative temperatures (−2°C) under increased salt concentration (10%). The results are discussed in relation to the possible inheritance of the adaptive characteristics acquired in specific environments.

Azospirillum thiophilum sp. nov., a diazotrophic bacterium isolated from a sulfide spring.

A novel nitrogen-fixing strain, designated BV-S(T), was isolated from a sulfur bacterial mat collected from a sulfide spring of the Stavropol Krai, North Caucasus, Russia. Strain BV-S(T) grew optimally at pH 7.5 and 37°C. According to the results of phylogenetic analysis, strain BV-S(T) belonged to the genus Azospirillum within the family Rhodospirillaceae of the class Alphaproteobacteria. Within the genus Azospirillum, strain BV-S(T) was most closely related to Azospirillum doebereinerae GSF71(T), A. picis IMMIB TAR-3(T) and A. lipoferum ATCC 29707(T) (97.7, 97.7 and 97.4 % 16S rRNA gene sequence similarity, respectively). DNA-DNA relatedness between strain BV-S(T) and A. doebereinerae DSM 13131(T), A. picis DSM 19922(T) and A. lipoferum ATCC 29707(T) was 38, 55 and 42 %, respectively. Similarities between nifH sequences of strain BV-S(T) and members of the genus Azospirillum ranged from 94.5 to 96.8 %. Chemotaxonomic characteristics (quinone Q-10, major fatty acid C(18 : 1)ω7c and G+C content 67 mol%) were similar to those of members of the genus Azospirillum. In contrast to known Azospirillum species, strain BV-S(T) was capable of mixotrophic growth under microaerobic conditions with simultaneous utilization of organic substrates and thiosulfate as electron donors for energy conservation. Oxidation of sulfide was accompanied by deposits of sulfur globules within the cells. Based on these observations, strain BV-S(T) is considered as a representative of a novel species of the genus Azospirillum, for which the name Azospirillum thiophilum sp. nov. is proposed. The type strain is BV-S(T) (=DSM 21654(T) =VKM B-2513(T)).

Grouping of Frankia strains on the basis of DNA relatedness

Summary The diversity among 27 Frankia strains was estimated by DNA-DNA hybridization (membrane filter method) and by determining DNA base compositions. The guanine + cytosine contents of DNA ranged from 69 to 73 mol%. The levels of DNA relatedness ranged from 3 to 100%, which allowed us to differentiate nine genospecies. Five genospecies were delineated among 18 strains compatible with plants of the genus Alnus (isolates from Alnus and Comptonia) and four genospecies were delineated among 9 strains compatible with plants of the family Elaeagnaceae (isolates from Elaeagnus, Hippophae, Shepherdia, and Colletia). Two additional strains were assigned to certain genospecies, since their total DNA restriction banding patterns and restriction fragment length polymorphism profiles were identical to those of representatives of these genospecies. The levels of DNA relatedness between members of the same genospecies ranged from 64 to 100%. In the Alnus host compatibility group, three genospecies displayed relatedness at the level of about 30% but were only 7 to 17% related to two other genospecies represented by single strains. In the Elaeagnaceae host compatibility group, strains from three genospecies showed relatedness at the levels of 15 to 36% but were only about 5% related to the fourth genospecies represented by a single strain. Low degrees of relatedness (3 to 20%) were also found between representatives of the two different host compatibility groups. The genospecies delineated cannot receive the status of nomenspecies, since few phenotypic criteria are available for their differentiation.

Rhodobaca barguzinensis sp. nov., a new alkaliphilic purple nonsulfur bacterium isolated from a soda lake of the Barguzin Valley (Buryat Republic, Eastern Siberia)

A novel strain, alga-05, of alkaliphilic purple nonsulfur bacteria was isolated from sediments of a small saline (60 g/l) soda lake near Lake Algin (Barguzin Valley, Buryat Republic, Russia). These bacteria contain bacteriochlorophyll a and carotenoids of the alternative spirilloxanthin group with predominating demethylspheroidenone. They are facultative anaerobes; their photosynthetic structures are of the vesicular type and arranged along the cell periphery. Growth of this strain is possible in a salinity range of 5–80 g/l NaCl, with an optimum at 20 g/l NaCl. Best growth occurred at 20–35°C. Analysis of the 16S rRNA gene sequences demonstrated that the studied isolate is closely related to the alkaliphilic purple nonsulfur bacterium Rhodobaca bogoriensis (99% similarity) isolated from soda lakes of the African Rift Zone. According to the results of DNA-DNA hybridization, strain alga-05 has a 52% similarity with the type species of the genus Rhodobaca. On the basis of the obtained genotypic data and some phenotypic properties (dwelling in a hypersaline soda lake of Siberia, moderate halophily, ability to grow at relatively low temperatures, etc.), the isolated strain of purple bacteria was described as a new species of the genus Rhodobaca, Rca. barguzinensis sp. nov.

A new species of actinomycete, Amycolata alni

A new species of the genus Amycolata, Amycolata alni, is proposed for strains which were mostly isolated from root nodules and rhizospheres of alder trees and were formerly assigned to the species Amycolata autotrophica. Strains of this new species could be differentiated from representatives of A. autotrophica by deoxyribonucleic acid homology data (17 to 29% relatedness), as well as by their ability to grow on salicin and D-gluconate, their failure to produce acid from cellobiose and meso-inositol, their resistance to penicillin and carbenicillin (10 g/ml), and other characteristics. Phenotypic features and low levels of deoxyribonucleic acid homology distinguish A. alni from two other species of the genus Amycolata, Amycolata saturnea and Amycolata hydrocarbonoxydans. The type strain of A. alni is strain 3LS (= VKM Ac-901).

Thiothrix caldifontis sp. nov. and Thiothrix lacustris sp. nov., gammaproteobacteria isolated from sulfide springs

Five strains of filamentous, sulfur-oxidizing bacteria were isolated from sulfur mats of different sulfide springs from various regions of the Northern Caucasus, Russia. A phylogenetic analysis based on 16S rRNA gene sequence comparison showed that all of the isolates are affiliated with the filamentous, colourless, sulfur-oxidizing bacteria of the genus Thiothrix within the Gammaproteobacteria and are closely related to Thiothrix fructosivorans. All strains are capable of growing heterotrophically, lithoautotrophically with thiosulfate or sulfide as the sole energy source and mixotrophically. Strains G1(T), G2, P and K2 are able to fix molecular nitrogen, but strain BL(T) is not. Randomly amplified polymorphic DNA (RAPD)-PCR analysis was used to assess the level of genetic relationships among the Thiothrix isolates. The Nei and Li similarity index revealed high genetic similarity among strains G1(T), G2, P and K2 (above 75 %), indicating that they are closely related. In combination with physiological and morphological data, strains G1(T), G2, P and K2 can be considered as members of the same species. The lowest genetic similarity (approx. 20 %) was reached between strain BL(T) and the other isolated Thiothrix strains. Strains BL(T) and G1(T) shared 35 % DNA-DNA relatedness and showed 51 and 53 % relatedness, respectively, to Thiothrix fructosivorans ATCC 49749. On the basis of this polyphasic analysis, strains G1(T), G2, P and K2 represent a novel species within the genus Thiothrix, for which the name Thiothrix caldifontis sp. nov. is proposed, with strain G1(T) (=DSM 21228(T) =VKM B-2520(T)) as the type strain. In addition, strain BL(T) represents a second novel species, Thiothrix lacustris sp. nov., with strain BL(T) (=DSM 21227(T) =VKM B-2521(T)) as the type strain.

[Seasonal changes in the structure of the anoxygenic photosynthetic bacterial community in Lake Shunet, Khakassia].

Seasonal studies of the anoxygenic phototrophic bacterial community of the water column of the saline eutrophic meromictic Lake Shunet (Khakassia) were performed in 2002 (June) and 2003 (February–March and August). From the redox zone down, the lake water was of dark green color. Green sulfur bacteria predominated in every season. The maximum number of green sulfur bacteria was 107 cells/ml in summer and 106 cells/ml in winter. A multi-syringe stratification sampler was applied for the study of the fine vertical distribution of phototrophs in August 2003; the sampling was performed every 5 cm. A 5-cm-thick pink-colored water layer inhabited by purple sulfur bacteria was shown to be located above the layer of green bacteria. The species composition and ratio of purple bacterial species depended on the sampling depth and on the season. In summer, the number of purple sulfur bacteria in the layer of pink water was 1.6 × 108 cells/ml. Their number in winter was 3 × 105 cells/ml. In the upper oxygen-containing layer of the chemocline the cells of purple nonsulfur bacteria were detected in summer. The maximum number of nonsulfur purple bacteria, 5 × 102 cells/ml, was recorded in August 2003. According to the results of the phylogenetic analysis of pure cultures of the isolated phototrophic bacteria, which were based on 16S rDNA sequencing, green sulfur bacteria were close to Prosthecochloris vibrioformis, purple sulfur bacteria, to Thiocapsa and Halochromatium species, and purple nonsulfur bacteria, to Rhodovulum euryhalinum and Pinkicyclus mahoneyensis.

Changes in the Fine Structure of Microbial Cells Induced by Chaotropic Salts

The electron microscopic examination of thin sections of cells of the yeasts Saccharomyces cerevisiae and Pichia pastoris and the gram-positive bacteria Micrococcus luteus and Bacillus subtilis showed that cell treatment with the chaotropic salts guanidine hydrochloride (6 M) and guanidine thiocyanate (4 M) at 37°C for 3–5 h or at 100°C for 5–6 min induced degradative processes, which affected almost all cellular structures. The cell wall, however, retained its ultrastructure, integrity, and rigidity, due to which the morphology of cells treated with the chaotropic salts did not change. High-molecular-weight DNA was localized in a new cell compartment, the ectoplasm (a peripheral hydrophilic zone). The chaotropic salts destroyed the outer and inner membranes and partially degraded the outer and inner protein coats of Bacillus subtilis spores, leaving their cortex (the murein layer) unchanged. The spore core became accessible to stains and showed the presence of regions with high and low electron densities. The conditions of cell treatment with the chaotropic salts were chosen to provide for efficient in situ PCR analysis of the 16S and 18S rRNA genes with the use of oligonucleotide primers.