[Show abstract][Hide abstract] ABSTRACT: The bacterial stringent response is triggered by deficiencies of available nutrients and other environmental stresses. It is mediated by 5'-triphosphate-guanosine-3'-diphosphate and 5'-diphosphate-guanosine-3'-diphosphate (collectively (p)ppGpp) and generates global changes in gene expression and metabolism that enable bacteria to adapt to and survive these challenges. Borrelia burgdorferi encounters multiple stressors in its cycling between ticks and mammals that could trigger the stringent response. We have previously shown that the B. burgdorferi stringent response is mediated by a single enzyme, RelBbu, with both (p)ppGpp synthase and hydrolase activities, and that a B. burgdorferi 297 relBbu null deletion mutant was defective in adapting to stationary phase, incapable of down-regulating synthesis of rRNA and could not infect mice. We have now used this deletion mutant and microarray analysis to identify genes comprising the rel regulon in B. burgdorferi cultured at 34°C, and found that transcription of genes involved in glycerol metabolism is induced by relBbu. Culture of the wild type parental strain, the relBbu deletion mutant and its complemented derivative at 34°C and 25°C in media containing glucose or glycerol as principal carbon sources revealed a growth defect in the mutant, most evident at the lower temperature. Transcriptional analysis of the glp operon for glycerol uptake and metabolism in these three strains confirmed that relBbu was necessary and sufficient to increase transcription of this operon in the presence of glycerol at both temperatures. These results confirm and extend previous findings regarding the stringent response in B. burgdorferi. They also demonstrate that the stringent response regulates glycerol metabolism in this organism and is likely crucial for its optimal growth in ticks.
[Show abstract][Hide abstract] ABSTRACT: Borrelia burgdorferi, the agent of Lyme disease, is maintained in nature within an enzootic cycle involving a mammalian reservoir and an Ixodes sp. tick vector. The transmission, survival and pathogenic potential of B. burgdorferi depend on the bacterium's ability to modulate its transcriptome as it transits between vector and reservoir host. Herein, we employed an amplification-microarray approach to define the B. burgdorferi transcriptomes in fed larvae, fed nymphs and in mammalian host-adapted organisms cultivated in dialysis membrane chambers. The results show clearly that spirochetes exhibit unique expression profiles during each tick stage and during cultivation within the mammal; importantly, none of these profiles resembles that exhibited by in vitro-grown organisms. Profound shifts in transcript levels were observed for genes encoding known or predicted lipoproteins as well as proteins involved in nutrient uptake, carbon utilization and lipid synthesis. Stage-specific expression patterns of chemotaxis-associated genes also were noted, suggesting that the composition and interactivities of the chemotaxis machinery components vary considerably in the feeding tick and mammal. The results as a whole make clear that environmental sensing by B. burgdorferi directly or indirectly drives an extensive and tightly integrated modulation of cell envelope constituents, chemotaxis/motility machinery, intermediary metabolism and cellular physiology. These findings provide the necessary transcriptional framework for delineating B. burgdorferi regulatory pathways throughout the enzootic cycle as well as defining the contribution(s) of individual genes to spirochete survival in nature and virulence in humans.
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No preview · Article · Nov 2014 · Molecular Microbiology
[Show abstract][Hide abstract] ABSTRACT: The persistence of dormant, noncultivable Borrelia burgdorferi after ceftriaxone treatment was examined. B. burgdorferi isolates were cultivated in Barbour-Stoenner-Kelly medium in the presence or absence of ceftriaxone, and cultures were monitored
for up to 56 days. Viability of B. burgdorferi was assessed by subculture, growth, morphology, and pH (as a surrogate for metabolic activity). In addition, the presence
of B. burgdorferi DNA and mRNA was assayed by PCR and by real-time reverse transcription (RT)-PCR, respectively. Spirochetes could not be successfully
subcultured by day 3 after exposure to ceftriaxone. In cultures treated with ceftriaxone, the pH of the culture medium did
not change through day 56, whereas it declined by at least 1 pH unit by 14 days in untreated cultures. These results suggest
that B. burgdorferi viability is rapidly eliminated after antibiotic treatment. Nevertheless, DNA was detected by B. burgdorferi-specific PCR for up to 56 days in aliquots from both ceftriaxone-treated and untreated cultures. In addition, although ceftriaxone
treatment resulted in a reduction in the quantities of transcript for ospC, ospA, flaB, and pfk, certain mRNAs could be detected through day 14. Transcript for all 4 genes was essentially undetectable after 28 days of
treatment. Taken together, the results suggest that B. burgdorferi DNA and mRNA can be detected in samples long after spirochetes are no longer viable as assessed by classic microbiological
parameters. PCR positivity in the absence of culture positivity following antibiotic treatment in animal and human studies
should be interpreted with caution.
Preview · Article · Dec 2012 · Journal of clinical microbiology
[Show abstract][Hide abstract] ABSTRACT: Lyme disease, the most commonly reported tick-borne infection in North America, is caused by infection with the spirochete Borrelia burgdorferi. Although an accurate clinical diagnosis can often be made based on the presence of erythema migrans, in research studies microbiologic or molecular microbiologic confirmation of the diagnosis may be required. In this study, we evaluated the sensitivity of 5 direct diagnostic methods (culture and nested polymerase chain reaction [PCR] of a 2-mm skin biopsy specimen, nested PCR and quantitative PCR (qPCR) performed on the same 1-mL aliquot of plasma and a novel qPCR-blood culture method) in 66 untreated adult patients with erythema migrans. Results of one or more of these tests were positive in 93.9% of the patients. Culture was more sensitive than PCR for both skin and blood, but the difference was only statistically significant for blood samples (P<0.005). Blood culture was significantly more likely to be positive in patients with multiple erythema migrans skin lesions compared to those with a single lesion (P=0.001). Positive test results among the 48 patients for whom all 5 assays were performed invariably included either a positive blood or a skin culture. The results of this study demonstrate that direct detection methods such as PCR and culture are highly sensitive in untreated adult patients with erythema migrans. This enabled microbiologic or molecular microbiologic confirmation of the diagnosis of B. burgdorferi infection in all but 4 (6.1%) of the 66 patients evaluated.
No preview · Article · May 2012 · Diagnostic microbiology and infectious disease
[Show abstract][Hide abstract] ABSTRACT: Bloodstream invasion is an important event in the pathogenesis of the more serious manifestations of Lyme disease. The number of spirochetes in the blood of infected patients, however, has not been determined, and, therefore, it is unknown whether the number of spirochetes can be correlated with particular clinical or laboratory features. This study was designed to measure the level of Borrelia burgdorferi in the plasma of Lyme disease patients and correlate these levels with selected clinical and laboratory findings. Nested and quantitative polymerase chain reaction (qPCR) was employed to detect cell-associated flaB gene DNA in the plasma of untreated early Lyme disease patients with erythema migrans (EM). Twenty-nine (45.3%) of 64 patients had evidence of B. burgdorferi in their plasma by at least one of the PCR methods. For the 22 qPCR-positive patients, the mean number of flaB gene copies per mL of plasma was 4,660, with a range of 414 to 56,000. The number of flaB gene copies did not significantly correlate with any of the clinical, demographic, or laboratory variables assessed. For reasons discussed, we suggest caution in extrapolating an estimate of the number of viable Borrelia in plasma from the observed number of flaB copies.
No preview · Article · Aug 2011 · European Journal of Clinical Microbiology
[Show abstract][Hide abstract] ABSTRACT: Borrelia burgdorferi, the spirochetal agent of Lyme disease, is a vector-borne pathogen that cycles between a mammalian host and tick vector. This complex life cycle requires that the spirochete modulate its gene expression program to facilitate growth and maintenance in these diverse milieus. B. burgdorferi contains an operon that is predicted to encode proteins that would mediate the uptake and conversion of glycerol to dihydroxyacetone phosphate. Previous studies indicated that expression of the operon is elevated at 23°C and is repressed in the presence of the alternative sigma factor RpoS, suggesting that glycerol utilization may play an important role during the tick phase. This possibility was further explored in the current study by expression analysis and mutagenesis of glpD, a gene predicted to encode glycerol 3-phosphate dehydrogenase. Transcript levels for glpD were significantly lower in mouse joints relative to their levels in ticks. Expression of GlpD protein was repressed in an RpoS-dependent manner during growth of spirochetes within dialysis membrane chambers implanted in rat peritoneal cavities. In medium supplemented with glycerol as the principal carbohydrate, wild-type B. burgdorferi grew to a significantly higher cell density than glpD mutant spirochetes during growth in vitro at 25°C. glpD mutant spirochetes were fully infectious in mice by either needle or tick inoculation. In contrast, glpD mutants grew to significantly lower densities than wild-type B. burgdorferi in nymphal ticks and displayed a replication defect in feeding nymphs. The findings suggest that B. burgdorferi undergoes a switch in carbohydrate utilization during the mammal to tick transition. Further, the results demonstrate that the ability to utilize glycerol as a carbohydrate source for glycolysis during the tick phase of the infectious cycle is critical for maximal B. burgdorferi fitness.
[Show abstract][Hide abstract] ABSTRACT: Approximately 45% of untreated United States patients with early Lyme disease associated with erythema migrans have a positive
blood culture based on microscopic detection of Borrelia burgdorferi in Barbour-Stoenner-Kelly medium after 2 to 12 weeks of incubation. In this study we demonstrate that the yield of blood
cultures can be significantly increased to 70.8% by the use of a combined culture-quantitative PCR technique and that among
those patients found to have a positive blood culture, positivity was detected in over 90% within just 7 days of incubation.
Patients with multiple erythema migrans were almost uniformly culture positive by this technique.
Preview · Article · Jun 2011 · Journal of clinical microbiology
[Show abstract][Hide abstract] ABSTRACT: The genome of Borrelia burgdorferi, the causative agent of Lyme disease, is comprised of a large linear chromosome and numerous smaller linear and circular
plasmids. B. burgdorferi exhibits substantial genomic variation, and previous studies revealed genotype-specific variation at the right chromosomal
telomere. A correlation has also been established between genotype and invasiveness. The correlation between chromosome length
and genotype and between genotype and invasiveness suggested that a gene(s) at the right chromosome telomere may be required
for virulence. Of particular interest was bb0844, an RpoS-regulated gene at the right telomere, the expression of which is induced when the spirochete undergoes adaptation
to the mammalian host. The structure of the right chromosomal telomere was examined in 53 B. burgdorferi clinical isolates of various genotypes. Four distinct patterns were observed for bb0844: (i) chromosomal localization, (ii) plasmid localization, (iii) presence on both chromosome and plasmid, and (iv) complete
absence. These patterns correlated with the B. burgdorferi genotype. On the basis of available sequence data, we propose a mechanism for the genomic rearrangements that accounts for
the variability in bb0844 genomic localization. To further explore the role of BB0844 in the spirochete life cycle, a bb0844 deletion mutant was constructed by allelic exchange, and the viability of wild-type and bb0844 deletion mutants was examined in an experimental mouse-tick infection model. The bb0844 mutant was fully infectious in C3H/HeJ mice by either needle inoculation or tick transmission with B. burgdorferi-infected Ixodes scapularis larvae. Naïve larval ticks acquired both wild-type and mutant spirochetes with equal efficiency from B. burgdorferi-infected mice. The results demonstrate that BB0844 is not required for spirochete viability, pathogenicity, or maintenance
in the tick vector or the mammalian host. At present, a defined role for BB0844 in B. burgdorferi cannot be ascertained.
Full-text · Article · Mar 2011 · Infection and immunity
[Show abstract][Hide abstract] ABSTRACT: Lyme disease (LD) is a tick-borne infection caused by the bacterial pathogen Borrelia burgdorferi. Current diagnostic tests mostly use borrelial lysates or select antigens to detect serum antibodies against B. burgdorferi. These immunoassays are not entirely effective, especially for detection of early infection. We have recently characterized an in vivo-induced antigen, BBK07, as a serodiagnostic marker for LD. We now report that in a line blot assay, recombinant BBK07 protein-based detection is 90% sensitive and nearly 100% specific against B. burgdorferi infection in humans. Using an overlapping peptide library of 23 peptides encompassing full-length BBK07, we identified the immunodominant epitopes of BBK07 during human infection. We show that a select combination of amino-terminal peptides significantly enhanced BBK07-based diagnostic accuracy compared to that with the full-length protein. Although in enzyme-linked immunosorbent assay (ELISA) studies BBK07 peptides had overall lower sensitivity than established serodiagnostic peptides, such as the VlsE peptide C6 and OspC peptide pepC10, for the detection of early human LD, a subset of serum samples that failed to recognize either VlsE or OspC peptides were preferentially reactive to BBK07 peptides. These results highlight the fact that BBK07 peptides could be useful to complement the efficacy of VlsE and OspC peptide-based serodiagnostic assays. Finally, using a panel of canine sera, we show that BBK07 peptide is also effective for LD diagnosis in infected dogs. Together, our data show that peptides from the B. burgdorferi surface protein BBK07 are highly specific and sensitive serodiagnostic markers, and we suggest their future use in LD diagnostic assays.
Preview · Article · Dec 2010 · Clinical and vaccine Immunology: CVI
[Show abstract][Hide abstract] ABSTRACT: The Borrelia burgdorferi Rrp1 protein is a diguanylate cyclase that controls a regulon consisting of approximately 10% of the total genome. Because Rrp1 lacks a DNA-binding domain, its regulatory capability is most likely mediated through the production of bis-(3'-5')-cyclic dimeric GMP (c-di-GMP). C-di-GMP binds to and activates the regulatory activity of proteins that harbor a PilZ domain. The occurrence of a PilZ domain within a protein is not in and of itself sufficient to convey c-di-GMP binding, as other structural aspects of the protein are important in the interaction. In this study, we have assessed the expression and c-di-GMP binding ability of the sole PilZ domain-containing protein of B. burgdorferi B31, PlzA. PlzA was determined to be upregulated by tick feeding and to be expressed during mammalian infection. The gene is highly conserved and present in all Borrelia species. Analyses of recombinant PlzA demonstrated its ability to bind c-di-GMP and site-directed mutagenesis revealed that this interaction is highly specific and dependent on Arg residues contained within the PilZ domain. In summary, this study is the first to identify a c-di-GMP effector molecule in a spirochete and provides additional evidence for the existence of a complete c-di-GMP regulatory network in the Lyme disease spirochete, B. burgdorferi.
Full-text · Article · Mar 2010 · FEMS Immunology & Medical Microbiology
[Show abstract][Hide abstract] ABSTRACT: Although BBA74 initially was described as a 28-kDa virulence-associated outer-membrane-spanning protein with porin-like function,
subsequent studies revealed that it is periplasmic and downregulated in mammalian host-adapted spirochetes. To further elucidate
the role of this protein in the Borrelia burgdorferi tick-mammal cycle, we conducted a thorough examination of its expression profile in comparison with the profiles of three
well-characterized, differentially expressed borrelial genes (ospA, ospC, and ospE) and their proteins. In vitro, transcripts for bba74 were expressed at 23°C and further enhanced by a temperature shift (37°C), whereas BBA74 protein diminished at elevated temperatures;
in contrast, neither transcript nor protein was expressed by spirochetes grown in dialysis membrane chambers (DMCs). Primer
extension of wild-type B. burgdorferi grown in vitro, in conjunction with expression analysis of DMC-cultivated wild-type and rpoS mutant spirochetes, revealed that, like ospA, bba74 is transcribed by σ70 and is subject to RpoS-mediated repression within the mammalian host. A series of experiments utilizing wild-type and rpoS mutant spirochetes was conducted to determine the transcriptional and translational profiles of bba74 during the tick-mouse cycle. Results from these studies revealed (i) that bba74 is transcribed by σ70 exclusively during the larval and nymphal blood meals and (ii) that transcription of bba74 is bracketed by RpoS-independent and -dependent forms of repression that are induced by arthropod- and mammalian host-specific
signals, respectively. Although loss of BBA74 does not impair the ability of B. burgdorferi to complete its infectious life cycle, the temporal compartmentalization of this gene's transcription suggests that BBA74
facilitates fitness of the spirochete within a narrow window of its tick phase. A reexamination of the paradigm for reciprocal
regulation of ospA and ospC, performed herein, revealed that the heterogeneous expression of OspA and OspC displayed by spirochete populations during
the nymphal blood meal results from the intricate sequence of transcriptional and translational changes that ensue as B. burgdorferi transitions between its arthropod vector and mammalian host.
Full-text · Article · Mar 2009 · Journal of bacteriology
[Show abstract][Hide abstract] ABSTRACT: Lyme disease pathogenesis results from a complex interaction between Borrelia burgdorferi and the host immune system. The intensity and nature of the inflammatory response of host immune cells to B. burgdorferi may be a determining factor in disease progression. Gene array analysis was used to examine the expression of genes encoding cytokines, chemokines, and related factors in the joint tissue of infected C3H/HeJ mice and in a murine macrophage-like cell line in response to a disseminating or attenuated clinical isolate of B. burgdorferi. Both isolates elicited a robust proinflammatory response in RAW264.7 cells characterized by an increase in transcript levels of genes encoding CC and CXC chemokines, proinflammatory cytokines, and TNF superfamily members. Transcription of genes encoding IL-1beta, IL-6, MCP-1, MIP-1alpha, CXCR4, and TLR2 induced in RAW264.7 cells by either live or heat-killed spirochetes did not differ significantly at any time point over a 24-h period, nor was there a difference in the protein levels of IL-10, TNF-alpha, IL-6, and IL-12p70 in culture supernatants. Thus, induction of host macrophage expression of proinflammatory mediators by host macrophages does not contribute to the differential pathogenicity of different B. burgdorferi strains.
Full-text · Article · Jun 2008 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Lyme borreliosis in North America is caused by the tick-borne spirochete Borrelia burgdorferi, a zoonotic bacterium that is able to persistently infect a wide range of vertebrate species. Given the pronounced strain
structure of B. burgdorferi in the northeastern United States, we asked whether the fitness of the different genotypes varies among susceptible vertebrate
hosts. The transmission dynamics of two genetically divergent human isolates of B. burgdorferi, BL206 and B348, were analyzed experimentally in white-footed mice and in C3H/HeNCrl mice over a time period of almost 3
months. We found that the initially high transmission efficiency from white-footed mice to ticks declined sharply for isolate
B348 but remained considerably high for isolate BL206. In contrast, in C3H/HeNCrl mice, high transmission efficiency persisted
for both isolates. Our findings provide proof-of-principle evidence for intrinsic fitness variation of B. burgdorferi strains in vertebrate host species, perhaps indicating the beginnings of adaptive radiation.
Full-text · Article · Feb 2008 · Applied and Environmental Microbiology
[Show abstract][Hide abstract] ABSTRACT: Borrelia burgdorferi (Bb) adapts to its arthropod and mammalian hosts by altering its transcriptional and antigenic profiles in response to environmental signals associated with each of these milieus. In studies presented here, we provide evidence to suggest that mammalian host signals are important for modulating and maintaining both the positive and negative aspects of mammalian host adaptation mediated by the alternative sigma factor RpoS in Bb. Although considerable overlap was observed between genes induced by RpoS during growth within the mammalian host and following temperature-shift, comparative microarray analyses demonstrated unequivocally that RpoS-mediated repression requires mammalian host-specific signals. A substantial portion of the in vivo RpoS regulon was uniquely upregulated within dialysis membrane chambers, further underscoring the importance of host-derived environmental stimuli for differential gene expression in Bb. Expression profiling of genes within the RpoS regulon by quantitative reverse transcription polymerase chain reaction (qRT-PCR) revealed a level of complexity to RpoS-dependent gene regulation beyond that observed by microarray, including a broad range of expression levels and the presence of genes whose expression is only partially dependent on RpoS. Analysis of Bb-infected ticks by qRT-PCR established that expression of rpoS is induced during the nymphal blood meal but not within unfed nymphs or engorged larvae. Together, these data have led us to postulate that RpoS acts as a gatekeeper for the reciprocal regulation of genes involved in the establishment of infection within the mammalian host and the maintenance of spirochetes within the arthropod vector.
Preview · Article · Oct 2007 · Molecular Microbiology
[Show abstract][Hide abstract] ABSTRACT: Clinical and murine studies suggest that there is a differential pathogenicity of different genotypes of Borrelia burgdorferi, the spirochetal agent of Lyme disease. Comparative genome hybridization was used to explore the relationship between different
genotypes. The chromosomes of all studied isolates were highly conserved (>93%) with respect to both sequence and gene order.
Plasmid sequences were substantially more diverse. Plasmids lp54, cp26, and cp32 were present in all tested isolates, and
their sequences and gene order were conserved. The majority of linear plasmids showed variation both in terms of presence
among different isolates and in terms of sequence and gene order. The data strongly imply that all B. burgdorferi clinical isolates contain linear plasmids related to each other, but the structure of these replicons may vary substantially
from isolate to isolate. These alterations include deletions and presumed rearrangements that are likely to result in unique
plasmid elements in many isolates. There is a strong correlation between complete genome hybridization profiles and other
typing methods, which, in turn, also correlate to differences in pathogenicity. Because there is substantially less variation
in the chromosomal and circular plasmid portions of the genome, the major differences in open reading frame content and genomic
diversity among isolates are linear plasmid driven.
Preview · Article · Sep 2006 · Journal of Bacteriology
[Show abstract][Hide abstract] ABSTRACT: Borrelia burgdorferi, the etiologic agent of Lyme disease, is genetically heterogeneous. Previous studies have shown a significant association between the frequency of hematogenous dissemination in Lyme disease patients and the genotype of the infecting B. burgdorferi strain. Comparative transcriptional profiling of two representative clinical isolates with distinct genotypes (BL206 and B356) was undertaken. A total of 78 open reading frames (ORFs) had expression levels that differed significantly between the two isolates. A number of genes with potential involvement in nutrient uptake (BB0603, BBA74, BB0329, BB0330, and BBB29) have significantly higher expression levels in isolate B356. Moreover, nearly 25% of the differentially expressed genes are predicted to be localized on the cell surface, implying that these two isolates have cell surface properties that differ considerably. One of these genes, BBA74, encodes a protein of 257 amino acid residues that has been shown to possess porin activity. BBA74 transcript level was >20-fold higher in B356 than in BL206, and strain B356 contained three- to fivefold more BBA74 protein. BBA74 was disrupted by the insertion of a kanamycin resistance cassette into the coding region. The growth rates of both wild-type and mutant strains were essentially identical, and cultures reached the same final cell densities. However, the mutant strains consistently showed prolonged lags of 2 to 5 days prior to the induction of log-phase growth compared to wild-type strains. It is tempting to speculate that the absence of BBA74 interferes with the enhanced nutrient uptake that may be required for the entry of cells into log-phase growth. These studies demonstrate the value of comparative transcriptional profiling for identifying differences in the transcriptomes of B. burgdorferi clinical isolates that may provide clues to pathogenesis. The 78 ORFs identified here are a good starting point for the investigation of factors involved in the hematogenous dissemination of B. burgdorferi.
Full-text · Article · Nov 2005 · Infection and Immunity
[Show abstract][Hide abstract] ABSTRACT: The effects of variations in Barbour-Stoenner-Kelly (BSK) medium on the infectivity and pathogenicity of Borrelia burgdorferi clinical isolates were assessed by retrospective and prospective studies using a murine model of Lyme borreliosis. Thirty
of 35 (86%) mice infected with any of six virulent B. burgdorferi clinical isolates grown in a BSK-H medium developed clinically apparent arthritis. By contrast, arthritis was observed in
only 25 of 60 (42%) mice inoculated with two of these B. burgdorferi strains grown in a different lot of BSK-H medium (P < 0.001). In a prospective study, mice inoculated with a B. burgdorferi clinical isolate grown in a BSK medium prepared in-house produced significantly greater disease than those injected with
the same isolate cultured in BSK-H medium (P < 0.05). The attenuated pathogenicity is not due to the loss of plasmids during in vitro cultivation. The data suggest that
variations in BSK medium have a significant impact on the infectivity and pathogenicity of B. burgdorferi clinical isolates.
Preview · Article · Dec 2004 · Infection and Immunity
[Show abstract][Hide abstract] ABSTRACT: The genome of Borrelia burgdorferi, the etiologic agent of Lyme disease, is composed of a linear chromosome and more than 20 linear and circular plasmids. Typically,
plasmid content analysis has been carried out by pulsed-field gel electrophoresis and confirmed by Southern hybridization.
However, multiple plasmids of virtually identical sizes (e.g., lp28 and cp32) complicate the interpretation of such data.
The present study was undertaken to investigate the complete plasmid complements of B. burgdorferi clinical isolates cultivated from patients from a single region where early Lyme disease is endemic. A total of 21 isolates
obtained from the skin biopsy or blood samples of Lyme disease patients were examined for their complete plasmid complements
by Southern hybridization and plasmid-specific PCR analysis. All clinical isolates harbored at least six of the nine previously
characterized cp32s. Fourteen isolates harbored all B31-like linear plasmids, and seven isolates simultaneously lacked lp56,
lp38, and some segments of lp28-1. The distinctive plasmid profile observed in these seven isolates was specific to organisms
that had ribosomal spacer type 2 and pulsed-field gel type A, which implies a clonal origin for this genotype. The presence
of nearly identical complements of multiple linear and circular plasmids in all of the human isolates suggests that these
plasmids may be particularly necessary for infection, adaptation, and/or maintenance in the infected host.
Full-text · Article · Aug 2003 · Infection and Immunity
[Show abstract][Hide abstract] ABSTRACT: The pathogenicity of Borrelia burgdorferi sensu stricto clinical isolates representing 2 distinct ribosomal DNA spacer restriction fragment–length polymorphism genotypes
(RSTs) was assessed in a murine model of Lyme disease. B. burgdorferi was recovered from 71.5% and 26.6% of specimens from mice infected with RST1 and RST3 isolates, respectively (P<.0001). The
average ankle diameter and histologic scores for carditis and arthritis were significantly higher after 2 weeks of infection
among mice infected with RST1 isolates than among those infected with RST3 isolates (P<.001). These clinical manifestations
were associated with larger numbers of spirochetes in target tissues but not with the serum sensitivity of the individual
isolates. Thus, the development and severity of disease in genetically identical susceptible hosts is determined mainly by
the pathogenic properties of the infecting B. burgdorferi isolate. The RST1 genotype is genetically homogeneous and thus may represent a recently evolved clonal lineage that is highly
pathogenic in humans and animals
Full-text · Article · Sep 2002 · The Journal of Infectious Diseases
[Show abstract][Hide abstract] ABSTRACT: Borrelia burgdorferi spends a significant proportion of its life cycle within an ixodid tick, which has a cuticle containing chitin, a polymer
of N-acetylglucosamine (GlcNAc). TheB. burgdorferi celA, celB, andcelC genes encode products homologous to transporters for cellobiose and chitobiose (the dimer subunit of chitin) in other bacteria,
which could be useful for bacterial nutrient acquisition during growth within ticks. We found that chitobiose efficiently
substituted for GlcNAc during bacterial growth in culture medium. We inactivated the celB gene, which encodes the putative membrane-spanning component of the transporter, and compared growth of the mutant in various
media to that of its isogenic parent. The mutant was no longer able to utilize chitobiose, while neither the mutant nor the
wild type can utilize cellobiose. We propose renaming the three genes chbA,chbB, and chbC, since they probably encode a chitobiose transporter. We also found that thechbC gene was regulated in response to growth temperature and during growth in medium lacking GlcNAc.
Preview · Article · Nov 2001 · Journal of Bacteriology