The Experts below are selected from a list of 150 Experts worldwide ranked by ideXlab platform
Kevin Dybvig - One of the best experts on this subject based on the ideXlab platform.
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Interaction of cationic antimicrobial peptides with Mycoplasma pulmonis
FEBS letters, 2013Co-Authors: Ho Jin Park, Kevin Dybvig, Ki Mo Kang, Bok Luel Lee, Yong Woo Jung, In Hee LeeAbstract:We investigated the mode of action underlying the anti-Mycoplasma activity of cationic antimicrobial peptides (AMPs) using four known AMPs and Mycoplasma pulmonis as a model Mycoplasma. Scanning electron microscopy revealed that the integrity of the M. pulmonis membrane was significantly damaged within 30 min of AMPs exposure, which was confirmed by measuring the uptake of propidium iodine into the Mycoplasma cells. The anti-Mycoplasma activity of AMPs was found to depend on the binding affinity for phosphatidylcholine, which was incorporated into the Mycoplasma membrane from the growth medium and preferentially distributed in the outer leaflet of the lipid bilayer.
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eps i polysaccharide protects Mycoplasma pulmonis from phagocytosis
Fems Microbiology Letters, 2013Co-Authors: Brandon M. Shaw, Warren L. Simmons, James M. Daubenspeck, Kevin DybvigAbstract:Few Mycoplasmal polysaccharides have been described and little is known about their role in pathogenesis. The infection of mice with Mycoplasma pulmonis has been utilized in many in vivo and in vitro studies to gain a better understanding of host–pathogen interactions during chronic respiratory infection. Although alveolar macrophages have a primary role in host defence, M. pulmonis is killed inefficiently in vitro. One antiphagocytic factor produced by the Mycoplasma is the family of phase- and size-variable Vsa lipoproteins. However, bacteria generally employ multiple strategies for combating host defences, with capsular polysaccharide often having a key role. We show here that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibit increased susceptibility to binding and subsequent killing by alveolar macrophages. These results give further insight into how Mycoplasmas are able to avoid the host immune system and sustain a chronic infection.
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EPS‐I polysaccharide protects Mycoplasma pulmonis from phagocytosis
FEMS microbiology letters, 2012Co-Authors: Brandon M. Shaw, Warren L. Simmons, James M. Daubenspeck, Kevin DybvigAbstract:Few Mycoplasmal polysaccharides have been described and little is known about their role in pathogenesis. The infection of mice with Mycoplasma pulmonis has been utilized in many in vivo and in vitro studies to gain a better understanding of host–pathogen interactions during chronic respiratory infection. Although alveolar macrophages have a primary role in host defence, M. pulmonis is killed inefficiently in vitro. One antiphagocytic factor produced by the Mycoplasma is the family of phase- and size-variable Vsa lipoproteins. However, bacteria generally employ multiple strategies for combating host defences, with capsular polysaccharide often having a key role. We show here that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibit increased susceptibility to binding and subsequent killing by alveolar macrophages. These results give further insight into how Mycoplasmas are able to avoid the host immune system and sustain a chronic infection.
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Mycoplasma pulmonis Vsa proteins and polysaccharide modulate adherence to pulmonary epithelial cells.
FEMS microbiology letters, 2012Co-Authors: Jeffrey R. Bolland, Kevin DybvigAbstract:The Mycoplasma pulmonis Vsa proteins are a family of size- and phase-variable lipoproteins that shield the Mycoplasmas from complement and modulate attachment to abiotic surfaces. Mycoplasmas producing a long Vsa protein hemadsorb poorly and yet are proficient at colonizing rats and mice. The effect of the length of the Vsa protein on the attachment of Mycoplasmas to epithelial cells has not been previously explored. We find that independent of Vsa isotype, Mycoplasmas producing a long Vsa protein with many tandem repeats adhere poorly to murine MLE-12 cells compared with Mycoplasmas producing a short Vsa. We also find that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibited decreased adherence to MLE-12 cells, even though it has been shown previously that such mutants have an enhanced ability to form a biofilm.
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The Vsa Shield of Mycoplasma pulmonis Is Antiphagocytic
Infection and immunity, 2011Co-Authors: Brandon M. Shaw, Warren L. Simmons, Kevin DybvigAbstract:The infection of mice with Mycoplasma pulmonis is a model for studying chronic Mycoplasmal respiratory disease. Many in vivo and in vitro studies have used the organism to gain a better understanding of host-pathogen interactions in chronic respiratory infection. The organism's Vsa proteins contain an extensive tandem repeat region. The length of the tandem repeat unit varies from as few as 11 amino acids to as many as 19. The number of tandem repeats can be as high as 60. The number of repeats varies at a high frequency due to slipped-strand mispairing events that occur during DNA replication. When the number of repeats is high, e.g., 40, the Mycoplasma is resistant to lysis by complement but does not form a robust biofilm. When the number of repeats is low, e.g., 5, the Mycoplasma is killed by complement when the cells are dispersed but has the capacity to form a biofilm that resists complement. Here, we examine the role of the Vsa proteins in the avoidance of phagocytosis and find that cells producing a protein with many tandem repeats are relatively resistant to killing by macrophages. These results may be pertinent to understanding the functions of similar proteins that have extensive repeat regions in other microbes.
C. Todd French - One of the best experts on this subject based on the ideXlab platform.
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Large-scale transposon mutagenesis of Mycoplasma pulmonis
Molecular microbiology, 2008Co-Authors: C. Todd French, Ping Lao, Ann E. Loraine, Brian T. Matthews, Kevin DybvigAbstract:To obtain mutants for the study of the basic biology and pathogenic mechanisms of Mycoplasmas, the insertion site of transposon Tn4001T was determined for 1700 members of a library of Mycoplasma pulmonis mutants. After evaluating several criteria for gene disruption, we concluded that 321 of the 782 protein coding regions were inactivated. The dispensable and essential genes of M. pulmonis were compared with those reported for Mycoplasma genitalium and Bacillus subtilis. Perhaps the most surprising result of the current study was that unlike other bacteria, ribosomal proteins S18 and L28 were dispensable. Carbohydrate transport and the susceptibility of selected mutants to UV irradiation were examined to assess whether active transposition of Tn4001T within the genome would confound phenotypic analysis. In contrast to earlier reports suggesting that Mycoplasmas were limited in their DNA repair machinery, mutations in recA, uvrA, uvrB and uvrC resulted in a DNA-repair deficient phenotype. A mutant with a defect in transport of N-acetylglucosamine was identified.
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Evidence for type III restriction and modification systems in Mycoplasma pulmonis
Journal of bacteriology, 2007Co-Authors: Kevin Dybvig, Zuhua Cao, C. Todd FrenchAbstract:Mycoplasma pulmonis possesses a cassette of genes that are predicted to code for type III restriction and modification (R-M) enzymes. Transposon disruption of a gene predicted to code for the endonuclease subunit of the enzyme resulted in loss of R-M activity. Genomic data indicate that the cassette was acquired by horizontal gene transfer and possibly located on a mobile element.
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Gene transfer in Mycoplasma pulmonis.
Journal of bacteriology, 2002Co-Authors: Amy M. Teachman, C. Todd French, Warren L. Simmons, Kevin DybvigAbstract:Experiments were undertaken to examine gene transfer in Mycoplasma pulmonis. Parent strains containing transposon-based tetracycline and chloramphenicol resistance markers were combined to allow transfer of markers. Two mating protocols were developed. The first consisted of coincubating the strains in broth culture for extended periods of time. The second protocol consisted of a brief incubation of the combined strains in a 50% solution of polyethylene glycol. Using either protocol, progeny that had acquired antibiotic resistance markers from both parents were obtained. Analysis of the progeny indicated that only the transposon and not flanking genomic DNA was transferred to the recipient cell. Gene transfer was DNase resistant and probably the result of conjugation or cell fusion.
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Construction and use of derivatives of transposon Tn4001 that function in Mycoplasma pulmonis and Mycoplasma arthritidis.
Journal of bacteriology, 2000Co-Authors: Kevin Dybvig, C. Todd French, L L VoelkerAbstract:Previous attempts to introduce transposon Tn4001 into Mycoplasma pulmonis and Mycoplasma arthritidis have not been successful, possibly due to functional failure of the transposon's gentamicin resistance determinant. Tn4001C and Tn4001T were constructed, respectively, by insertion of a chloramphenicol acetyltransferase gene and the tetM tetracycline resistance determinant into Tn4001. Both Tn4001C and Tn4001T transposed in M. pulmonis, and Tn4001T transposed in M. arthritidis. The incorporation of a Tn4001T derivative that contained lacZ into either Mycoplasma species resulted in transformants with readily detectable LacZ activity. Tn4001T may be of general utility for use as a Mycoplasma cloning vehicle because tetM functions in all species of Mycoplasma examined thus far.
Gail H. Cassell - One of the best experts on this subject based on the ideXlab platform.
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Mycoplasma pulmonis possesses a novel chemoattractant for B lymphocytes.
Infection and immunity, 1992Co-Authors: S E Ross, Jerry W. Simecka, G. P. Gambill, Gail H. CassellAbstract:Mycoplasma pulmonis causes chronic murine respiratory mycoplasmosis, which is characterized by extensive peribronchial and perivascular infiltration of mononuclear cells, including B lymphocytes. B-lymphocyte recruitment into sites of inflammation is presently poorly understood but must involve directed chemotaxis of these cells in response to some external recruitment stimulus. In these studies, picogram amounts of M. pulmonis membrane protein were found to possess potent chemoattractant activity for resting rat B lymphocytes. This report is the first description of a bacterially derived chemoattractant for B lymphocytes and offers a unique opportunity to study regulation of B-lymphocyte recruitment to a site of chronic pulmonary inflammation. Furthermore, M. pulmonis membrane activation of fresh rat serum was found to produce a potent stimulus for recruitment of peritoneal and alveolar macrophages. M. pulmonis-mediated recruitment of lymphocytes and macrophages may play a significant role in the pathogenesis of murine respiratory mycoplasmosis, a role in which organisms on the bronchiolar epithelial surfaces may release proteins which can directly or indirectly promote chemotaxis of inflammatory cells from the circulation.
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Cytopathic effects of Mycoplasma pulmonis in vivo and in vitro.
Infection and immunity, 1991Co-Authors: C. T. K. H. Stadtlander, J W Simecka, Harold L. Watson, Gail H. CassellAbstract:This study was performed to evaluate the cytopathic features resulting from Mycoplasma pulmonis infection of tracheal organ cultures compared to with those seen in in vivo infection and to use this system to determine possible differences in cytopathic effects in two M. pulmonis variants found to cause different diseases in vivo. The attachment of M. pulmonis to respiratory epithelium was similar in vivo and in vitro. Cytopathic effects seen in both systems were also similar in loss of tight junctions between cells and exfoliation of respiratory cells, resulting in exposure of the subepithelial layer. These similarities indicate that the observed tissue damage is initiated by the Mycoplasmas rather than by immunologic host responses but does not exclude the possibility that host responses may subsequently contribute to the cytopathological events. Comparison of the effects of the two variants (one known to cause death in vivo) did not reveal differences in vitro. This suggests that host factors (not present in vitro) may account for differences in virulence. Detailed in vitro studies allowed the identification of the time frame corresponding to the in vivo infection and also revealed the limitations of the in vitro system.
Warren L. Simmons - One of the best experts on this subject based on the ideXlab platform.
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eps i polysaccharide protects Mycoplasma pulmonis from phagocytosis
Fems Microbiology Letters, 2013Co-Authors: Brandon M. Shaw, Warren L. Simmons, James M. Daubenspeck, Kevin DybvigAbstract:Few Mycoplasmal polysaccharides have been described and little is known about their role in pathogenesis. The infection of mice with Mycoplasma pulmonis has been utilized in many in vivo and in vitro studies to gain a better understanding of host–pathogen interactions during chronic respiratory infection. Although alveolar macrophages have a primary role in host defence, M. pulmonis is killed inefficiently in vitro. One antiphagocytic factor produced by the Mycoplasma is the family of phase- and size-variable Vsa lipoproteins. However, bacteria generally employ multiple strategies for combating host defences, with capsular polysaccharide often having a key role. We show here that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibit increased susceptibility to binding and subsequent killing by alveolar macrophages. These results give further insight into how Mycoplasmas are able to avoid the host immune system and sustain a chronic infection.
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EPS‐I polysaccharide protects Mycoplasma pulmonis from phagocytosis
FEMS microbiology letters, 2012Co-Authors: Brandon M. Shaw, Warren L. Simmons, James M. Daubenspeck, Kevin DybvigAbstract:Few Mycoplasmal polysaccharides have been described and little is known about their role in pathogenesis. The infection of mice with Mycoplasma pulmonis has been utilized in many in vivo and in vitro studies to gain a better understanding of host–pathogen interactions during chronic respiratory infection. Although alveolar macrophages have a primary role in host defence, M. pulmonis is killed inefficiently in vitro. One antiphagocytic factor produced by the Mycoplasma is the family of phase- and size-variable Vsa lipoproteins. However, bacteria generally employ multiple strategies for combating host defences, with capsular polysaccharide often having a key role. We show here that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibit increased susceptibility to binding and subsequent killing by alveolar macrophages. These results give further insight into how Mycoplasmas are able to avoid the host immune system and sustain a chronic infection.
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The Vsa Shield of Mycoplasma pulmonis Is Antiphagocytic
Infection and immunity, 2011Co-Authors: Brandon M. Shaw, Warren L. Simmons, Kevin DybvigAbstract:The infection of mice with Mycoplasma pulmonis is a model for studying chronic Mycoplasmal respiratory disease. Many in vivo and in vitro studies have used the organism to gain a better understanding of host-pathogen interactions in chronic respiratory infection. The organism's Vsa proteins contain an extensive tandem repeat region. The length of the tandem repeat unit varies from as few as 11 amino acids to as many as 19. The number of tandem repeats can be as high as 60. The number of repeats varies at a high frequency due to slipped-strand mispairing events that occur during DNA replication. When the number of repeats is high, e.g., 40, the Mycoplasma is resistant to lysis by complement but does not form a robust biofilm. When the number of repeats is low, e.g., 5, the Mycoplasma is killed by complement when the cells are dispersed but has the capacity to form a biofilm that resists complement. Here, we examine the role of the Vsa proteins in the avoidance of phagocytosis and find that cells producing a protein with many tandem repeats are relatively resistant to killing by macrophages. These results may be pertinent to understanding the functions of similar proteins that have extensive repeat regions in other microbes.
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Identification of exopolysaccharide-deficient mutants of Mycoplasma pulmonis.
Molecular microbiology, 2009Co-Authors: James M. Daubenspeck, Warren L. Simmons, Jeffrey R. Bolland, Wenyi Luo, Kevin DybvigAbstract:Summary The presence of capsular exopolysaccharide (EPS) in Mollicutes has been inferred from electron micrographs for over 50 years without conclusive data to support the production of complex carbohydrates by the organism. Mycoplasma pulmonis binds the lectin Griffonia simplicifolia I (GS-I), which is specific for terminal β-linked galactose residues. Mutants that failed to produce the EPS bound by GS-I were isolated from a transposon library. All of the mutants had the transposon located in open reading frame MYPU_7410 or MYPU_7420. These overlapping genes are predicted to code for a heterodimeric pair of ABC transporter permeases and may code for part of a new pathway for synthesis of EPS. Analysis by lectin-affinity chromatography in conjunction with gas chromatography demonstrated that the wild-type Mycoplasma produced an EPS (EPS-I) composed of equimolar amounts of glucose and galactose that was lacking in the mutants. Phenotypic analysis revealed that the mutants had an increased propensity to form a biofilm on glass surfaces, colonized mouse lung and trachea efficiently, but had a decreased association with the A549 lung cell line. Confounding the interpretation of these results is the observation that the mutants missing EPS-I had an eightfold overproduction of an apparent second EPS (EPS-II) containing N-acetylglucosamine.
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Biofilms Protect Mycoplasma pulmonis Cells from Lytic Effects of Complement and Gramicidin
Infection and immunity, 2007Co-Authors: Warren L. Simmons, Kevin DybvigAbstract:The length of the tandem repeat region of the Vsa protein of Mycoplasma pulmonis has previously been shown to modulate the susceptibility of Mycoplasmas to killing by complement: cells that produce a short form of the Vsa protein are highly sensitive, and cells producing the long Vsa protein are resistant. In contrast to their differing susceptibilities to complement, the Mycoplasmas were highly sensitive to gramicidin irrespective of the length of the Vsa protein produced. We show here that when encased within a biofilm, cells of M. pulmonis producing a short form of the Vsa protein were more resistant to complement and gramicidin than Mycoplasmas that were dispersed. The resistance appeared to be localized to those Mycoplasmas within tower structures of the biofilms. Biofilm formation may be a mechanism that protects Mycoplasmas from host immunity.
Jeffrey R. Bolland - One of the best experts on this subject based on the ideXlab platform.
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Mycoplasma pulmonis Vsa proteins and polysaccharide modulate adherence to pulmonary epithelial cells.
FEMS microbiology letters, 2012Co-Authors: Jeffrey R. Bolland, Kevin DybvigAbstract:The Mycoplasma pulmonis Vsa proteins are a family of size- and phase-variable lipoproteins that shield the Mycoplasmas from complement and modulate attachment to abiotic surfaces. Mycoplasmas producing a long Vsa protein hemadsorb poorly and yet are proficient at colonizing rats and mice. The effect of the length of the Vsa protein on the attachment of Mycoplasmas to epithelial cells has not been previously explored. We find that independent of Vsa isotype, Mycoplasmas producing a long Vsa protein with many tandem repeats adhere poorly to murine MLE-12 cells compared with Mycoplasmas producing a short Vsa. We also find that mutants lacking the EPS-I polysaccharide of M. pulmonis exhibited decreased adherence to MLE-12 cells, even though it has been shown previously that such mutants have an enhanced ability to form a biofilm.
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Identification of exopolysaccharide-deficient mutants of Mycoplasma pulmonis.
Molecular microbiology, 2009Co-Authors: James M. Daubenspeck, Warren L. Simmons, Jeffrey R. Bolland, Wenyi Luo, Kevin DybvigAbstract:Summary The presence of capsular exopolysaccharide (EPS) in Mollicutes has been inferred from electron micrographs for over 50 years without conclusive data to support the production of complex carbohydrates by the organism. Mycoplasma pulmonis binds the lectin Griffonia simplicifolia I (GS-I), which is specific for terminal β-linked galactose residues. Mutants that failed to produce the EPS bound by GS-I were isolated from a transposon library. All of the mutants had the transposon located in open reading frame MYPU_7410 or MYPU_7420. These overlapping genes are predicted to code for a heterodimeric pair of ABC transporter permeases and may code for part of a new pathway for synthesis of EPS. Analysis by lectin-affinity chromatography in conjunction with gas chromatography demonstrated that the wild-type Mycoplasma produced an EPS (EPS-I) composed of equimolar amounts of glucose and galactose that was lacking in the mutants. Phenotypic analysis revealed that the mutants had an increased propensity to form a biofilm on glass surfaces, colonized mouse lung and trachea efficiently, but had a decreased association with the A549 lung cell line. Confounding the interpretation of these results is the observation that the mutants missing EPS-I had an eightfold overproduction of an apparent second EPS (EPS-II) containing N-acetylglucosamine.
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A stochastic mechanism for biofilm formation by Mycoplasma pulmonis
Journal of bacteriology, 2006Co-Authors: Warren L. Simmons, James M. Daubenspeck, Jeffrey R. Bolland, Kevin DybvigAbstract:Bacterial biofilms are communities of bacteria that are enclosed in an extracellular matrix. Within a biofilm the bacteria are protected from antimicrobials, environmental stresses, and immune responses from the host. Biofilms are often believed to have a highly developed organization that is derived from differential regulation of the genes that direct the synthesis of the extracellular matrix and the attachment to surfaces. The Mycoplasmas have the smallest of the prokaryotic genomes and apparently lack complex gene-regulatory systems. We examined biofilm formation by Mycoplasma pulmonis and found it to be dependent on the length of the tandem repeat region of the variable surface antigen (Vsa) protein. Mycoplasmas that produced a short Vsa protein with few tandem repeats formed biofilms that attached to polystyrene and glass. Mycoplasmas that produced a long Vsa protein with many tandem repeats formed microcolonies that floated freely in the medium. The biofilms and the microcolonies contained an extracellular matrix which contained Vsa protein, lipid, DNA, and saccharide. As variation in the number of Vsa tandem repeats occurs by slipped-strand mispairing, the ability of the Mycoplasmas to form a biofilm switches stochastically.
