Taxonomy of the Lyme disease spirochetes.

Morphology, physiology, and DNA nucleotide composition of Lyme disease spirochetes, Borrelia, Treponema, and Leptospira were compared. Morphologically, Lyme disease spirochetes resemble Borrelia. They lack cytoplasmic tubules present in Treponema, and have more than one periplasmic flagellum per cell end and lack the tight coiling which are characteristic of Leptospira. Lyme disease spirochetes are also similar to Borrelia in being microaerophilic, catalase-negative bacteria. They utilize carbohydrates such as glucose as their major carbon and energy sources and produce lactic acid. Long-chain fatty acids are not degraded but are incorporated unaltered into cellular lipids. The diamino amino acid present in the peptidoglycan is ornithine. The mole % guanine plus cytosine values for Lyme disease spirochete DNA were 27.3-30.5 percent. These values are similar to the 28.0-30.5 percent for the Borrelia but differed from the values of 35.3-53 percent for Treponema and Leptospira. DNA reannealing studies demonstrated that Lyme disease spirochetes represent a new species of Borrelia, exhibiting a 31-59 percent DNA homology with the three species of North American borreliae. In addition, these studies showed that the three Lyme disease spirochetes comprise a single species with DNA homologies ranging from 76-100 percent. The three North American borreliae also constitute a single species, displaying DNA homologies of 75-95 percent. Lyme disease spirochetes and Borrelia exhibited little or no DNA homology (0-2 percent) with the Treponema or Leptospira. Plasmids were present in the three Lyme disease spirochetes and the three North American borreliae.     

Phylogenetic analysis of the spirochetes.

The 16S rRNA sequences were determined for species of Spirochaeta, Treponema, Borrelia, Leptospira, Leptonema, and Serpula, using a modified Sanger method of direct RNA sequencing. Analysis of aligned 16S rRNA sequences indicated that the spirochetes form a coherent taxon composed of six major clusters or groups. The first group, termed the treponemes, was divided into two subgroups. The first treponeme subgroup consisted of Treponema pallidum, Treponema phagedenis, Treponema denticola, a thermophilic spirochete strain, and two species of Spirochaeta, Spirochaeta zuelzerae and Spirochaeta stenostrepta, with an average interspecies similarity of 89.9%. The second treponeme subgroup contained Treponema bryantii, Treponema pectinovorum, Treponema saccharophilum, Treponema succinifaciens, and rumen strain CA, with an average interspecies similarity of 86.2%. The average interspecies similarity between the two treponeme subgroups was 84.2%. The division of the treponemes into two subgroups was verified by single-base signature analysis. The second spirochete group contained Spirochaeta aurantia, Spirochaeta halophila, Spirochaeta bajacaliforniensis, Spirochaeta litoralis, and Spirochaeta isovalerica, with an average similarity of 87.4%. The Spirochaeta group was related to the treponeme group, with an average similarity of 81.9%. The third spirochete group contained borrelias, including Borrelia burgdorferi, Borrelia anserina, Borrelia hermsii, and a rabbit tick strain. The borrelias formed a tight phylogenetic cluster, with average similarity of 97%. THe borrelia group shared a common branch with the Spirochaeta group and was closer to this group than to the treponemes. A single spirochete strain isolated fromt the shew constituted the fourth group. The fifth group was composed of strains of Serpula (Treponema) hyodysenteriae and Serpula (Treponema) innocens. The two species of this group were closely related, with a similarity of greater than 99%. Leptonema illini, Leptospira biflexa, and Leptospira interrogans formed the sixth and most deeply branching group. The average similarity within this group was 83.2%. This study represents the first demonstration that pathogenic and saprophytic Leptospira species are phylogenetically related. The division of the spirochetes into six major phylogenetic clusters was defined also by sequence signature elements. These signature analyses supported the conclusion that the spirochetes represent a monophylectic bacterial phylum.     

Bacterial γ-glutamyltranspeptidases: Comparison of Escherichia coli and Pseudomonasγ-glutamyltranspeptidase

Serpulina (Treponema) hyodysenteriae strain A-1 partially purified rRNA, labelled with photobiotin, was used as a non-radioactive probe to identify the rRNA gene restriction patterns of S. hyodysenteriae strains and other spirochetes. Sau3A restriction enzyme digests resulted in similar rRNA gene restriction patterns in S. hyodysenteriae strains from five different countries. Some S. hyodysenteriae strains could be differentiated by variations in their rRNA gene restriction patterns after cleavage of DNA by restriction enzymes SspI or BglII. S. innocens and Treponema succinifaciens, non-pathogenic pig intestinal spirochetes, had rRNA gene restriction patterns that differed markedly from the S. hyodysenteriae patterns, and from each other.     

Taxonomy and pathogenicity of Erwinia cacticida sp. nov.

A total of 108 pectolytic, soft-rotting Erwinia strains were collected from 11 types of cacti growing in Arizona, Texas, northern Mexico, and Australia between 1958 and 1989. Four strains were collected from soils beneath or close to naturally rotting saguaro cacti. Collectively, these strains caused soft rots of saguaro, organ pipe, and senita cacti, Opuntia (cactus) fruits and pads, tomato fruits, and potato slices, but only occasionally caused soft rots of slices of carrot roots. A numerical cluster analysis showed that 98 of the 112 strains formed a uniform group (cluster 1A) that was distinguished from other pectolytic erwinias by an API 20E code of 1205131, by negative reactions in API 50CHE tests for L-arabinose, myo-inositol, D-cellobiose, melibiose, and D-raffinose, and, in supplemental tests, by positive reactions for malonate and growth at 43 degrees C. The average levels of DNA relatedness of 22 cluster 1A strains to the proposed type strain (strain 1-12) as determined by the hydroxyapatite method were 88% in 60 degrees C reactions (with 1% divergence within related sequences) and 87% in 75 degrees C reactions. The levels of relatedness to the type strains of other Erwinia spp. were less than or equal to 38% in 75 degrees C reactions. Cluster 1A strains also had a characteristic cellular fatty acid profile containing cyclo-(11,12)-nonadecanoic acid (C19:0 Cyclo C11-12) and missing tridecanoic acid (C13:0), heptadecanoic acid (C17:0), and cis-9-heptadecenoic acid (C17:1 CIS 9), which separated them from other pectolytic erwinias. Collectively, these data indicate that the members of cluster 1A are members of a new species, which we name Erwinia cacticida. Three cactus strains in cluster 1B appear to represent a second new species that is closely related to E. cacticida; these strains are designated E. cacticida-like pending the availability of additional strains for testing. The remaining cactus strains (in cluster 4) have the physiological, DNA, and fatty acid profiles of Erwinia carotovora.     

Glycerol-3-phosphate acquisition in spirochetes: distribution and biological activity of glycerophosphodiester phosphodiesterase (GlpQ) among Borrelia species

Relapsing-fever spirochetes achieve high cell densities (>10(8)/ml) in their host's blood, while Lyme disease spirochetes do not (<10(5)/ml). This striking contrast in pathogenicity of these two groups of bacteria suggests a fundamental difference in their ability to either exploit or survive in blood. Borrelia hermsii, a tick-borne relapsing-fever spirochete, contains orthologs to glpQ and glpT, genes that encode glycerophosphodiester phosphodiesterase (GlpQ) and glycerol-3-phosphate transporter (GlpT), respectively. In other bacteria, GlpQ hydrolyzes deacylated phospholipids to glycerol-3-phosphate (G3P) while GlpT transports G3P into the cytoplasm. Enzyme assays on 17 isolates of borreliae demonstrated GlpQ activity in relapsing-fever spirochetes but not in Lyme disease spirochetes. Southern blots demonstrated glpQ and glpT in all relapsing-fever spirochetes but not in the Lyme disease group. A Lyme disease spirochete, Borrelia burgdorferi, that was transformed with a shuttle vector containing glpTQ from B. hermsii produced active enzyme, which demonstrated the association of glpQ with the hydrolysis of phospholipids. Sequence analysis of B. hermsii identified glpF, glpK, and glpA, which encode the glycerol facilitator, glycerol kinase, and glycerol-3-phosphate dehydrogenase, respectively, all of which are present in B. burgdorferi. All spirochetes examined had gpsA, which encodes the enzyme that reduces dihydroxyacetone phosphate (DHAP) to G3P. Consequently, three pathways for the acquisition of G3P exist among borreliae: (i) hydrolysis of deacylated phospholipids, (ii) reduction of DHAP, and (iii) uptake and phosphorylation of glycerol. The unique ability of relapsing-fever spirochetes to hydrolyze phospholipids may contribute to their higher cell densities in blood than those of Lyme disease spirochetes.     

Brachyspira (Serpulina) hyodysenteriae gyrB mutants and interstrain transfer of coumermycin A(1) resistance

To further develop genetic techniques for the enteropathogen Brachyspira hyodysenteriae, the gyrB gene of this spirochete was isolated from a lambdaZAPII library of strain B204 genomic DNA and sequenced. The putative protein encoded by this gene exhibited up to 55% amino acid sequence identity with GyrB proteins of various bacterial species, including other spirochetes. B. hyodysenteriae coumermycin A(1)-resistant (Cn(r)) mutant strains, both spontaneous and UV induced, were isolated by plating B204 cells onto Trypticase soy blood agar plates containing 0.5 microg of coumermycin A(1)/ml. The coumermycin A(1) MICs were 25 to 100 microg/ml for the resistant strains and 0.1 to 0.25 microg/ml for strain B204. Four Cn(r) strains had single nucleotide changes in their gyrB genes, corresponding to GyrB amino acid changes of Gly(78) to Ser (two strains), Gly(78) to Cys, and Thr(166) to Ala. When Cn(r) strain 435A (Gly(78) to Ser) and Cm(r) Km(r) strain SH (DeltaflaA1::cat Deltanox::kan) were cultured together in brain heart infusion broth containing 10% (vol/vol) heat-treated (56 degrees C, 30 min) calf serum, cells resistant to chloramphenicol, coumermycin A(1), and kanamycin could be isolated from the cocultures after overnight incubation, but such cells could not be isolated from monocultures of either strain. Seven Cn(r) Km(r) Cm(r) strains were tested and were determined to have resistance genotypes of both strain 435A and strain SH. Cn(r) Km(r) Cm(r) cells could not be isolated when antiserum to the bacteriophage-like agent VSH-1 was added to cocultures, and the numbers of resistant cells increased fivefold when mitomycin C, an inducer of VSH-1 production, was added. These results indicate that coumermycin resistance associated with a gyrB mutation is a useful selection marker for monitoring gene exchange between B. hyodysenteriae cells. Gene transfer readily occurs between B. hyodysenteriae cells in broth culture, a finding with practical importance. VSH-1 is the likely mechanism for gene transfer.     

Reclassification of Treponema hyodysenteriae and Treponema innocens in a new genus, Serpula gen. nov., as Serpula hyodysenteriae comb. nov. and Serpula innocens comb. nov.

The intestinal anaerobic spirochetes Treponema hyodysenteriae B78T (T = type strain), B204, B169, and A-1, Treponema innocens B256T and 4/71, Treponema succinifaciens 6091T, and Treponema bryantii RUS-1T were compared by performing DNA-DNA reassociation experiments, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cell proteins, restriction endonuclease analysis of DNA, and 16S rRNA sequence analysis. DNA-DNA relative reassociation experiments in which the S1 nuclease method was used showed that T. hyodysenteriae B78T and B204 had 93% sequence homology with each other and approximately 40% sequence homology with T. innocens B256T and 4/71. Both T. hyodysenteriae B78T and T. innocens B256T exhibited negligible levels of DNA homology (less than or equal to 5%) with T. succinifaciens 6091T. The results of comparisons of protein electrophoretic profiles corroborated the DNA-DNA reassociation results. We found high levels of similarity (greater than or equal to 96%) in electrophoretic profiles among T. hyodysenteriae strains, moderate levels of similarity (43 to 49%) between T. hyodysenteriae and T. innocens, and no detectable similarity between the profiles of either T. hyodysenteriae or T. innocens and those of T. succinifaciens, T. bryantii, and Escherichia coli. Restriction endonuclease analysis of DNA was not useful in assessing genetic relationships since there was heterogeneity even between strains of T. hyodysenteriae. Partial 16S rRNA sequences of the intestinal spirochetes were determined by using a modified Sanger method and were compared in order to evaluate the phylogenetic relationships among these and other spirochetes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of spirochetes isolated from ticks (Ixodes tanuki, Ixodes turdus, and Ixodes columnae) and comparison of the sequences with those of Borrelia burgdorferi sensu lato strains.

Ixodes persulcatus serves as a tick vector for Borrelia garinii and Borrelia afzelii in Japan; however, unidentified spirochetes have been isolated from other species of ticks. In this study, 13 isolates from ticks (6 from Ixodes tanuki, 6 from Ixodes turdus, and 1 from Ixodes columnae) and 3 isolates from voles (Clethrionomys rufocanus) were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, rRNA gene restriction fragment length polymorphism, partial sequencing of the outer surface protein C (OspC) gene, whole DNA-DNA hybridization, and 16S rRNA gene sequence comparison. All of the results revealed that these Borrelia strains clearly represent at least two new species. A third is also likely, although additional strains have to be isolated and characterized before a separate species is designated. We designated all isolates of I. tanuki and C. rufocanus as group Hk501 and all isolates of I. turdus as group Ya501. Phylogenetic analysis based on 16S rRNA gene sequences distinguished these Borrelia strains from those belonging to hitherto known Borrelia species. Furthermore, the genomic groups, each with its own tick vectors with enzootic cycles, were quite different from each other and also from those of Lyme disease Borrelia species known to occur in Japan. The results of 16S rRNA gene sequence comparison suggest that the strain Am501 from I. columnae is related to group Hk501, although its level of DNA relatedness is less than 70%.     

Detection of bacteriophage VSH-1 svp38 gene in Brachyspira spirochetes

VSH-1 is a mitomycin C-inducible, non-lytic, phage-like agent that packages random 7.5-kb fragments of the Brachyspira hyodysenteriae genome. VSH-1 is the first recognized mechanism for gene transfer between B. hyodysenteriae cells. To analyze the distribution of VSH-1 among spirochetes, a 344-bp probe for gene svp38, encoding the VSH-1 major head protein, was amplified by polymerase chain reaction and used in Southern blot hybridizations with genomic DNA from various spirochete genera. The svp38 probe hybridized to a 40-kb SalI-SmaI fragment of the B. hyodysenteriae B78(T) chromosome, indicating VSH-1 DNA insertion into the chromosome at a unique site. Restriction endonuclease digested DNAs of 27 spirochete strains representing six Brachyspira species (B. hyodysenteriae, B. innocens, B. pilosicoli, B. murdochii, B. intermedia, B. alvinipulli) contained a single fragment hybridizing with the svp38 probe. DNAs from spirochete species of the genera Treponema, Spirochaeta, Borrelia, and Leptospira did not hybridize with the probe. VSH-1-like agents appear to be widely distributed among Brachyspira species and, as has been demonstrated for B. hyodysenteriae, may serve as useful gene transfer agents for those other species.     

Pantoea punctata sp. nov., Pantoea citrea sp. nov., and Pantoea terrea sp. nov. isolated from fruit and soil samples.

A total of 37 bacterial strains with the general characteristics of the family Enterobacteriaceae were isolated from fruit and soil samples in Japan as producers of 2,5-diketo-D-gluconic acid from D-glucose. These organisms were phenotypically most closely related to the genus Pantoea (F. Gavini, J. Mergaert, A. Beji, C. Mielearek, D. Izard, K. Kersters, and J. De Ley, Int. J. Syst. Bacteriol. 39:337-345, 1989) and were divided into three phenotypic groups. We selected nine representative strains from the three groups for an examination of DNA relatedness, as determined by the S1 nuclease method at 60 degrees C. Strain SHS 2003T (T = type strain) exhibited 30 to 41 and 28 to 33% DNA relatedness to the strains belonging to the strain SHS 2006T group (strains SHS 2004, SHS 2005, SHS 2006T, and SHS 2007) and to the strains belonging to the strain SHS 2008T group (strains SHS 2008T, SHS 2009, SHS 2010, and SHS 2011), respectively. Strain SHS 2006T exhibited 38 to 46% DNA relatedness to the strains belonging to the strain SHS 2008T group. The levels of DNA relatedness within the strain SHS 2006T group and within the strain SHS 2008T group were more than 85 and 71%, respectively. Strain SHS 2003T, SHS 2006T, and SHS 2008T DNAs exhibited less than 18% binding to Pantoea dispersa ATCC 14589T and Pantoea agglomerans ATCC 27155T DNAs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of Dutch porcine Serpulina (Treponema) isolates by restriction endonuclease analysis and DNA hybridization.

Genomes of 55 Dutch porcine Serpulina (Treponema) hyodysenteriae and non-pathogenic Serpulina isolates were characterized by restriction endonuclease analysis (REA) and DNA hybridization. The Dutch porcine isolates were compared with American Type Culture Collection (ATCC) strains of S. hyodysenteriae and S. innocens and isolates of S. hyodysenteriae with known serotypes (reference strains). REA of the Dutch S. hyodysenteriae isolates resulted in two main patterns, while the non-pathogenic isolates had many distinct REA patterns, all different from the S. hyodysenteriae strains. The S. hyodysenteriae reference strains all had distinct REA patterns, different from the Dutch strains. Upon Southern hybridization with a S. hyodysenteriae DNA fragment encoding a flagellar protein, all S. hyodysenteriae strains could be divided in two groups. The non-pathogenic Serpulina strains had many distinct hybridization patterns and hybridized less intensely. Upon hybridization with a S. hyodysenteriae DNA fragment encoding a haemolysin, DNA of all S. hyodysenteriae strains reacted in the same band. DNA of non-pathogenic Dutch Serpulina strains and S. innocens did not hybridize. It was concluded that there are two main genotypes of S. hyodysenteriae in the Netherlands. This could be of importance for recombinant DNA vaccine development.     

Vibrio navarrensis sp. nov., a species from sewage.

A group of 11 strains, mostly isolated from sewage water in the Province of Navarra, Spain, were found to constitute a DNA relatedness group which is 2 to 39% related to 23 species of the genus Vibrio and 2 to 3% related to two Aeromonas species. Phenotypically, these strains have all of the properties that define the genus Vibrio. However, they differ from the previously described species by three or more properties. The strains are negative for arginine, ornithine, and lysine decarboxylase activities and the Voges-Proskauer test and are unable to utilize putrescine, gluconate, glucuronate, and histidine. They utilize and produce acid from sucrose and grow at 40 degrees C. All strains grow in the presence of 0.5% (wt/vol) NaCl, and seven strains grow weakly in peptone water lacking NaCl. The group of strains which we studied can also be differentiated from other Vibrio species by fatty acid content. The G+C ratio of the DNA is 45 to 47 mol%. The name Vibrio navarrensis sp. nov. is proposed for these strains; strain 1397-6 (= CIP 103381) is the type strain.     

Detection of same sized 4.3 Kb extrachromosomal DNA elements in weakly beta-haemolytic human intestinal spirochaetes and Serpulina pilosicoli of swine origin

Agarose gel electrophoresis of total DNA from Italian strains of weakly beta-haemolytic human intestinal spirochaetes (w beta HIS) and porcine Serpulina pilosicoli reference strain P43/6/78 showed an extrachromosomal band having the same size and migrating at 4.3 Kb. The same results were observed after agarose gel electrophoresis of DNA obtained from the supernatant fluids of the spirochaetal cultures analysed. Swine Serpulina hyodysenteriae reference strain P18A was comparatively analysed and a 6.5 Kb extrachromosomal DNA element was found, as expected. Furthermore, S. hyodysenteriae reference strain P18A differed from all the other spirochaetes tested and had a higher number of flagella (8-12) at each cell end and was strongly beta-haemolytic. To the best of our knowledge, this is the first report on the detection of a band of extrachromosomal DNA having the same size in w beta HIS and S. pilosicoli from swine origin.     

Relatedness Among Rhizobium and Agrobacterium Species Determined by Three Methods of Nucleic Acid Hybridization

Deoxyribonucleic acid (DNA) was isolated from 20 strains of Rhizobium and Agrobacterium and from one strain of Serratia marcescens; the guanine plus cytosine content of each DNA sample was determined by thermal denaturation. Radioactive DNA was isolated from three reference strains following the uptake of [2-(14)C]thymidine in the presence of deoxyadenosine. Ribonucleic acid (RNA) polymerase was used to synthesize radioactive RNA on DNA templates from the three reference strains. Radioactive DNA and RNA from the three reference strains were each hybridized with filter-bound DNA from all of the 21 test strains in 6 x SSC (standard saline citrate) and 50% formamide at 43 C for 40 hr. DNA/DNA relatedness was also determined by spectrophotometric measurement of the rates of association of single-stranded DNA. The order of relatedness between strains was similar by each method. Overall standard deviations for the DNA/DNA and DNA/RNA membrane filter techniques were +/-0.87 and +/-1.03%, respectively; that for the spectrophotometric technique was +/-4.11%. The DNA/DNA membrane technique gave higher absolute values of hybridization than did the DNA/RNA technique. R. leguminosarum and R. trifolii could not be distinguished from each other by these techniques. These results also indicated close relationships between R. lupini and R. japonicum, and (with less certainty) between R. meliloti and R. phaseoli. Of all the rhizobia tested against the A. tumefaciens 371 reference strain, the R. japonicum strains were the most unrelated. The three Agrobacterium strains used were as related to the R. lupini and R. leguminosarum references as were several rhizobium strains.     

全沟硬蜱体内伯氏疏螺旋体的分离及特征

本文报道从黑龙江省全沟硬蜱分离的伯氏疏螺旋体H7株的特征。H7株细胞长9．8—26．5μm,宽0．1 3—0．35μm,有l—11个波,波长1．2—3．Oμm,波幅0．59一1．13μm,两端尖乩每端有7根鞭毛,菌体左旋。体外培养最适温度为31℃,具有2lk、32k、34k主要结构和抗原蛋白,能与新疆及黑龙江莱姆病人血清反应。这些结果表明,该菌株具备伯氏疏螺旋体的特征,它是与其它地区或媒介分离株不同的“亚型”。     

Recognition of Morganella subspecies, with proposal of Morganella morganii subsp. morganii subsp. nov. and Morganella morganii subsp. sibonii subsp. nov.

The genus name Morganella was established within the family Enterobacteriaceae in 1978. Morganella morganii is the only species described thus far within this genus, and the name M. morganii has been accepted by usage in the scientific community for strains previously known as Proteus morganii. M. morganii isolates differ in their abilities to ferment trehalose and exhibit variable lysine and ornithine decarboxylase patterns, emphasizing the phenotypic heterogeneity within this species. Previous genetic studies failed to reveal separate entities within the genus Morganella. We observed some trehalose-fermenting strains with different lysine and ornithine decarboxylase patterns. Two strains were lysine and ornithine positive, 3 were lysine positive and ornithine negative, and 29 were lysine negative and ornithine positive. These strains and 25 non-trehalose-fermenting strains with different lysine and ornithine decarboxylase patterns were investigated. DNA-DNA hybridization studies and phenotypic characterizations revealed that M. morganii can be separated into three DNA relatedness groups and seven biogroups. Strains from DNA relatedness group 1 were trehalose negative, and strains from DNA relatedness groups 2 and 3 were trehalose positive. One biogroup from DNA relatedness group 2 was phenotypically indistinguishable from DNA relatedness group 3. On the basis of these studies, we propose that M. morganii be subdivided into M. morganii subsp. morganii (type strain ATCC 25830) containing biogroups A, B, C, and D (DNA relatedness group 1) and M. morganii subsp. sibonii (type strain 8103-85; = ATCC 49948) containing biogroups E, F, and G (DNA relatedness groups 2 and 3).     

The bacterial nucleoid visualized by fluorescence microscopy of cells lysed within agarose: comparison of Escherichia coli and spirochetes of the genus Borrelia.

The nucleoids of Escherichia coli and the spirochetes Borrelia burgdorferi and Borrelia hermsii, agents of Lyme disease and relapsing fever, were examined by epifluorescence microscopy of bacterial cells embedded in agarose and lysed in situ with detergent and protease. The typical E. coli nucleoid was a rosette in which 20 to 50 long loops of DNA emanated from a dense node of DNA. The percentages of cells in a population having nucleoids with zero, one, two, and three nodes varied with growth rate and growth phase. The borrelia nucleoid, in contrast, was a loose network of DNA strands devoid of nodes. This nucleoid structure difference correlates with the unusual genome of Borrelia species, which consists primarily of linear replicons, including a 950-kb linear chromosome and linear plasmids. This method provides a simple, direct means to analyze the structure of the bacterial nucleoid.     

DNA relatedness among strains of the sweet potato pathogen Streptomyces ipomoea (Person and Martin 1940) Waksman and Henrici 1948.

DNA relatedness among 28 putative strains of Streptomyces ipomoea from geographically diverse locations and the type strain, NRRL B-12321, was determined spectrophotometrically. The data confirm that these 28 strains are not closely related genetically to the plant-pathogenic species Streptomyces scabies (39% DNA relatedness) or Streptomyces acidiscabies (17% DNA relatedness) or any other major blue-spored Streptomyces species (less than 30% DNA relatedness). Of the 29 strains examined, 4 could be clearly distinguished from S. ipomoea on the basis of morphological criteria, i.e., they had gray rather than blue spores and produced melanin pigment, and their low DNA relatedness to authentic S. ipomoea strains confirmed their original misidentification. The remaining 25 S. ipomoea strains exhibited high DNA relatedness among themselves (76 to 100% homology), even though they had been isolated in different locations throughout the United States and Japan. The avirulent type strain, NRRL B-12321, exhibited slightly lower DNA relatedness with the virulent strains of S. ipomoea (85% average DNA relatedness) than was observed among the virulent strains (average of 96% DNA relatedness).     

DNA relatedness among strains of the sweet potato pathogen Streptomyces ipomoea (Person and Martin 1940) Waksman and Henrici 1948.

DNA relatedness among 28 putative strains of Streptomyces ipomoea from geographically diverse locations and the type strain, NRRL B-12321, was determined spectrophotometrically. The data confirm that these 28 strains are not closely related genetically to the plant-pathogenic species Streptomyces scabies (39% DNA relatedness) or Streptomyces acidiscabies (17% DNA relatedness) or any other major blue-spored Streptomyces species (less than 30% DNA relatedness). Of the 29 strains examined, 4 could be clearly distinguished from S. ipomoea on the basis of morphological criteria, i.e., they had gray rather than blue spores and produced melanin pigment, and their low DNA relatedness to authentic S. ipomoea strains confirmed their original misidentification. The remaining 25 S. ipomoea strains exhibited high DNA relatedness among themselves (76 to 100% homology), even though they had been isolated in different locations throughout the United States and Japan. The avirulent type strain, NRRL B-12321, exhibited slightly lower DNA relatedness with the virulent strains of S. ipomoea (85% average DNA relatedness) than was observed among the virulent strains (average of 96% DNA relatedness).     

Outer surface protein polymorphisms linked to host‐spirochete association in Lyme borreliae

Lyme borreliosis is caused by multiple species of the spirochete bacteria Borrelia burgdorferi sensu lato. The spirochetes are transmitted by ticks to vertebrate hosts, including small‐ and medium‐sized mammals, birds, reptiles, and humans. Strain‐to‐strain variation in host‐specific infectivity has been documented, but the molecular basis that drives this differentiation is still unclear. Spirochetes possess the ability to evade host immune responses and colonize host tissues to establish infection in vertebrate hosts. In turn, hosts have developed distinct levels of immune responses when invaded by different species/strains of Lyme borreliae. Similarly, the ability of Lyme borreliae to colonize host tissues varies among different spirochete species/strains. One potential mechanism that drives this strain‐to‐strain variation of immune evasion and colonization is the polymorphic outer surface proteins produced by Lyme borreliae. In this review, we summarize research on strain‐to‐strain variation in host competence and discuss the evidence that supports the role of spirochete‐produced protein polymorphisms in driving this variation in host specialization. Such information will provide greater insights into the adaptive mechanisms driving host and Lyme borreliae association, which will lead to the development of interventions to block pathogen spread and eventually reduce Lyme borreliosis health burden.