scholarly journals Phenotypic Switching in Mycoplasma gallisepticum Hemadsorption Is Governed by a High-Frequency, Reversible Point Mutation

2003 ◽  
Vol 71 (3) ◽  
pp. 1265-1273 ◽  
Author(s):  
Florian Winner ◽  
Ivana Markovà ◽  
Peter Much ◽  
Albin Lugmair ◽  
Karin Siebert-Gulle ◽  
...  
Keyword(s):  
High Frequency ◽  
Stop Codon ◽  
Phase Variation ◽  
Mycoplasma Gallisepticum ◽  
Chronic Respiratory Disease ◽  
Transcription Unit ◽  
Phenotypic Switching ◽  
Base Substitution ◽  
Mutational Event ◽  
Repeated Motifs

ABSTRACT Mycoplasma gallisepticum is a flask-shaped organism that commonly induces chronic respiratory disease in chickens and infectious sinusitis in turkeys. Phenotypic switching in M. gallisepticum hemadsorption (HA) was found to correlate with phase variation of the GapA cytadhesin concurrently with that of the CrmA protein, which exhibits cytadhesin-related features and is encoded by a gene located downstream of the gapA gene as part of the same transcription unit. In clones derived from strain Rlow, detailed genetic analyses further revealed that on-off switching in GapA expression is governed by a reversible base substitution occurring at the beginning of the gapA structural gene. In HA− variants, this event generates a stop codon that results in the premature termination of GapA translation and consequently affects the expression of CrmA. Sequences flanking the mutation spot do not feature any repeated motifs that could account for error-prone mutation via DNA slippage and the exact mechanism underlying this high-frequency mutational event remains to be elucidated. An HA− mutant deficient in producing CrmA, mHAD3, was obtained by disrupting the crmA gene by using transposition mutagenesis. Despite a fully functional gapA gene, the amount of GapA detected in this mutant was considerably lower than in HA+ clonal variants, suggesting that, in absence of CrmA, GapA might be subjected to a higher turnover.

scholarly journals A surface epitope undergoing high-frequency phase variation is shared by Mycoplasma gallisepticum and Mycoplasma bovis.

1994 ◽  
Vol 62 (11) ◽  
pp. 4962-4968 ◽  
Author(s):  
D Yogev ◽  
D Menaker ◽  
K Strutzberg ◽  
S Levisohn ◽  
H Kirchhoff ◽  
...  
Keyword(s):  
High Frequency ◽  
Phase Variation ◽  
Mycoplasma Gallisepticum ◽  
Mycoplasma Bovis ◽  
Frequency Phase

scholarly journals Molecular Characterization of the Mycoplasma gallisepticum pvpA Gene Which Encodes a Putative Variable Cytadhesin Protein

2000 ◽  
Vol 68 (7) ◽  
pp. 3956-3964 ◽  
Author(s):  
S. Boguslavsky ◽  
D. Menaker ◽  
I. Lysnyansky ◽  
T. Liu ◽  
S. Levisohn ◽  
...  
Keyword(s):  
Amino Acids ◽  
Stop Codon ◽  
Size Variation ◽  
Phase Variation ◽  
Mycoplasma Genitalium ◽  
Mycoplasma Gallisepticum ◽  
Terminal Region ◽  
Repeated Sequences ◽  
Human Pathogens ◽  
Variable Surface

ABSTRACT A putative cytadhesin-related protein (PvpA) undergoing variation in its expression was identified in the avian pathogen Mycoplasma gallisepticum. The pvpA gene was cloned, expressed inEscherichia coli, and sequenced. It exhibits 54 and 52% homology with the P30 and P32 cytadhesin proteins of the human pathogens Mycoplasma pneumoniae and Mycoplasma genitalium, respectively. In addition, 50% homology was found with the MGC2 cytadhesin of M. gallisepticum and 49% homology was found with a stretch of 205 amino acids of the cytadherence accessory protein HMW3 of M. pneumoniae. The PvpA molecule possesses a proline-rich carboxy-terminal region (28%) containing two identical directly repeated sequences of 52 amino acids and a tetrapeptide motif (Pro-Arg-Pro-X) which is repeated 14 times. Genetic analysis of several clonal isolates representing different expression states of the PvpA product ruled out chromosomal rearrangement as the mechanism for PvpA phase variation. The molecular basis of PvpA variation was revealed in a short tract of repeated GAA codons, encoding five successive glutamate resides, located in the N-terminal region and subject to frequent mutation generating an in-frame UAA stop codon. Size variation of the PvpA protein was observed among M. gallisepticum strains, ranging from 48 to 55 kDa and caused by several types of deletions occurring at the PvpA C-terminal end and within the two directly repeated sequences. By immunoelectron microscopy, the PvpA protein was localized on the mycoplasma cell surface, in particular on the terminal tip structure. Collectively, these findings suggest that PvpA is a newly identified variable surface cytadhesin protein of M. gallisepticum.

scholarly journals Global Changes in Mycoplasma gallisepticum Phase-Variable Lipoprotein GenevlhAExpression duringIn VivoInfection of the Natural Chicken Host

2015 ◽  
Vol 84 (1) ◽  
pp. 351-355 ◽  
Author(s):  
K. Pflaum ◽  
E. R. Tulman ◽  
J. Beaudet ◽  
X. Liao ◽  
S. J. Geary
Keyword(s):  
Gene Expression ◽  
Phase Variation ◽  
Mycoplasma Gallisepticum ◽  
Chronic Respiratory Disease ◽  
Etiologic Agent ◽  
Economic Losses ◽  
Global Changes ◽  
Phase Variable ◽  
Content Type ◽  
Host Interaction

Mycoplasma gallisepticumis the primary etiologic agent of chronic respiratory disease in poultry, a disease largely affecting the respiratory tract and causing significant economic losses worldwide. Immunodominant proteins encoded by members of the variable lipoprotein and hemagglutinin (vlhA) gene family are thought to be important for mechanisms ofM. gallisepticum-host interaction, pathogenesis, and immune evasion, but their exact role and the overall nature of their phase variation are unknown. To better understand these mechanisms, we assessed global transcriptomicvlhAgene expression directly fromM. gallisepticumpopulations present on tracheal mucosae during a 7-day experimental infection in the natural chicken host. Here we report differences in both dominant and minorvlhAgene expression levels throughout the first week of infection and starting as early as day 1 postinfection, consistent with a functional role not dependent on adaptive immunity for driving phase variation. Notably, data indicated that, at given time points, specificvlhAgenes were similarly dominant in multiple independent hosts, suggesting a nonstochastic temporal progression of dominantvlhAgene expression in the colonizing bacterial population. The dominant expression of a givenvlhAgene was not dependent on the presence of 12-copy GAA trinucleotide repeats in the promoter region and did not revert to the predominatevlhAgene when no longer faced with host pressures. Overall, these data indicate thatvlhAphase variation is dynamic throughout the earliest stages of infection and that the pattern of dominantvlhAexpression may be nonrandom and regulated by previously unrecognized mechanisms.

scholarly journals No Change, No Life? What We Know about Phase Variation in Staphylococcus aureus

2021 ◽  
Vol 9 (2) ◽  
pp. 244
Author(s):  
Vishal Gor ◽  
Ryosuke L. Ohniwa ◽  
Kazuya Morikawa
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
High Frequency ◽  
Direct Evidence ◽  
Bacterial Species ◽  
Phase Variation ◽  
Opportunistic Pathogen ◽  
Adaptation Strategy ◽  
Innate Immune ◽  
Epigenetic Mechanisms

Phase variation (PV) is a well-known phenomenon of high-frequency reversible gene-expression switching. PV arises from genetic and epigenetic mechanisms and confers a range of benefits to bacteria, constituting both an innate immune strategy to infection from bacteriophages as well as an adaptation strategy within an infected host. PV has been well-characterized in numerous bacterial species; however, there is limited direct evidence of PV in the human opportunistic pathogen Staphylococcus aureus. This review provides an overview of the mechanisms that generate PV and focuses on earlier and recent findings of PV in S. aureus, with a brief look at the future of the field.

scholarly journals The medaka fish Tol2 transposable element is in an early stage of decay: identification of a nonautonomous copy

Genome ◽  
2021 ◽  
Author(s):  
Sakura Hayashi ◽  
Takuji Tsukiyama ◽  
Atsuo Iida ◽  
Masato Kinoshita ◽  
Akihiko Koga
Keyword(s):  
Amino Acid ◽  
Stop Codon ◽  
Early Stage ◽  
Single Amino Acid ◽  
Base Substitution ◽  
Unique Element ◽  
Medaka Fish ◽  
Medaka Genome ◽  
Single Amino Acid Change ◽  
Local Sequence

The majority of DNA-based transposable elements comprise autonomous and nonautonomous copies, or only nonautonomous copies, where the autonomous copy contains an intact gene for a transposase protein and the nonautonomous copy does not. Even if autonomous copies coexist, they are generally less frequent. The <i>Tol2</i> element of medaka fish is one of the few elements for which a nonautonomous copy has not yet been found. Here we report the presence of a nonautonomous <i>Tol2</i> copy that was identified by surveying the medaka genome sequence database. This copy contained 3 local sequence alterations that affected the deduced amino acid sequence of the transposase: a deletion of 15 nucleotides resulting in a deletion of 5 amino acids, a base substitution causing a single amino acid change, and another base substitution giving rise to a stop codon. Transposition assays using cultured human cells revealed that the transposase activity was reduced by the 15-nucleotide deletion and abolished by the nonsense mutation. This is the first example of a nonautonomous <i>Tol2</i> copy. Thus, <i>Tol2</i> is in an early stage of decay in the medaka genome, and is therefore a unique element to observe an almost whole decay process that progresses in natural populations.

Role of RpoS and MutS in phase variation of Pseudomonas sp. PCL1171

Microbiology ◽  
2005 ◽  
Vol 151 (5) ◽  
pp. 1403-1408 ◽  
Author(s):  
Daan van den Broek ◽  
Thomas F. C. Chin-A-Woeng ◽  
Guido V. Bloemberg ◽  
Ben J. J. Lugtenberg
Keyword(s):  
Growth Rate ◽  
High Frequency ◽  
Constitutive Expression ◽  
Phase Variation ◽  
Lag Phase ◽  
Pseudomonas Sp ◽  
Spontaneous Mutations ◽  
Stationary Growth ◽  
The Relationship

Pseudomonas sp. strain PCL1171 undergoes reversible colony phase variation between opaque phase I and translucent phase II colonies, which is dependent on spontaneous mutations in the regulatory genes gacA and gacS. Mutation of the mutS gene and constitutive expression of rpoS increases the frequency at which gac mutants appear 1000- and 10-fold, respectively. Experiments were designed to study the relationship between gacS, rpoS and mutS. These studies showed that (i) a functional gac system is required for the expression of rpoS, (ii) RpoS suppresses the expression of mutS and therefore increases the frequency of gac mutants, and (iii) upon mutation of rpoS and gacS, the expression of mutS is increased. Mutation of gacS abolishes suppression of mutS expression in stationary growth, suggesting that additional gac-dependent factors are involved in this suppression. In conclusion, inefficient mutation repair via MutS, of which the expression is influenced by gacA/S itself and by rpoS in combination with other factors, contributes to the high frequency of mutations accumulating in gacA/S. The role of RpoS in the growth advantage of a gac mutant was analysed, and mutation of rpoS only reduced the length of the lag phase, but did not affect the growth rate, suggesting a role for both RpoS and a reduction of metabolic load in the growth advantage of a gac mutant.

scholarly journals Role of the GapA and CrmA Cytadhesins of Mycoplasma gallisepticum in Promoting Virulence and Host Colonization

2013 ◽  
Vol 81 (5) ◽  
pp. 1618-1624 ◽  
Author(s):  
Ivana Indiková ◽  
Peter Much ◽  
László Stipkovits ◽  
Karin Siebert-Gulle ◽  
Michael P. Szostak ◽  
...  
Keyword(s):  
Point Mutation ◽  
Mycoplasma Gallisepticum ◽  
Chronic Respiratory Disease ◽  
Host Colonization ◽  
Content Type ◽  
Inner Organs ◽  
Avian Pathogen ◽  
Low Passage

ABSTRACTMycoplasma gallisepticumis an important avian pathogen that commonly induces chronic respiratory disease in chicken. To better understand the mycoplasma factors involved in host colonization, chickens were infected via aerosol with two hemadsorption-negative (HA−) mutants, mHAD3 and RCL2, that were derived from a low passage of the pathogenic strain R (Rlow) and are both deficient in the two major cytadhesins GapA and CrmA. After 9 days of infection, chickens were monitored for air sac lesions and for the presence of mycoplasmas in various organs. The data showed that mHAD3, in which thecrmAgene has been disrupted, did not promote efficient colonization or significant air sac lesions. In contrast, the spontaneous HA−RCL2 mutant, which contains a point mutation in thegapAstructural gene, successfully colonized the respiratory tract and displayed an attenuated virulence compared to that of Rlow. It has previously been shownin vitrothat the point mutation of RCL2 spontaneously reverts with a high frequency, resulting in on-and-off switching of the HA phenotype. Detailed analyses further revealed that such an event is not responsible for the observedin vivooutcome, since 98.4% of the mycoplasma populations recovered from RCL2-infected chickens still display the mutation and the associated phenotype. Unlike Rlow, however, RCL2 was unable to colonize inner organs. These findings demonstrate the major role played by the GapA and CrmA proteins inM. gallisepticumhost colonization and virulence.

scholarly journals Up-Regulation of miR-130b-3p Activates the PTEN/PI3K/AKT/NF-κB Pathway to Defense against Mycoplasma gallisepticum (HS Strain) Infection of Chicken

2018 ◽  
Vol 19 (8) ◽  
pp. 2172 ◽  
Author(s):  
Bo Yuan ◽  
Mengyun Zou ◽  
Yabo Zhao ◽  
Kang Zhang ◽  
Yingfei Sun ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Chicken Embryo ◽  
Mycoplasma Gallisepticum ◽  
Nuclear Factor Κb ◽  
Chronic Respiratory Disease ◽  
Luciferase Reporter ◽  
Sequencing Data ◽  
Infected Chicken ◽  
Functional Studies

Mycoplasma gallisepticum (MG) is the pathogen of chronic respiratory disease (CRD), hallmarked by vigorous inflammation in chickens, causing the poultry industry enormous losses. miRNAs have emerged as important regulators of animal diseases. Previous miRNA sequencing data has demonstrated that miR-130b-3p is up-regulated in MG-infected chicken embryo lungs. Therefore, we aimed to investigate the function of miR-130b-3p in MG infection of chickens. RT-qPCR results confirmed that miR-130b-3p was up-regulated both in MG-infected chicken embryo lungs and chicken embryonic fibroblast cells (DF-1 cells). Furthermore, functional studies showed that overexpression of miR-130b-3p promoted MG-infected DF-1 cell proliferation and cell cycle, whereas inhibition of miR-130b-3p weakened these cellular processes. Luciferase reporter assay combined with gene expression data supported that phosphatase and tensin homolog deleted on chromosome ten (PTEN) was a direct target of miR-130b-3p. Additionally, overexpression of miR-130b-3p resulted in up-regulations of phosphatidylinositol-3 kinase (PI3K), serine/threonine kinase (AKT), and nuclear factor-κB (NF-κB), whereas inhibition of miR-130b-3p led to the opposite results. Altogether, upon MG infection, up-regulation of miR-130b-3p activates the PI3K/AKT/NF-κB pathway, facilitates cell proliferation and cell cycle via down-regulating PTEN. This study helps to understand the mechanism of host response to MG infection.

The vsp Locus of Mycoplasma bovis: Gene Organization and Structural Features

1999 ◽  
Vol 181 (18) ◽  
pp. 5734-5741 ◽  
Author(s):  
Inessa Lysnyansky ◽  
Konrad Sachse ◽  
Ricardo Rosenbusch ◽  
Sharon Levisohn ◽  
David Yogev
Keyword(s):  
High Frequency ◽  
Sequence Similarity ◽  
Membrane Surface ◽  
Amino Acid Sequences ◽  
High Rate ◽  
Phenotypic Switching ◽  
Upstream Region ◽  
Mycoplasma Bovis ◽  
High Sequence Similarity ◽  
Polypeptide Structure

ABSTRACT Major lipoprotein antigens, known as variable membrane surface lipoproteins (Vsps), on the surface of the bovine pathogenMycoplasma bovis were shown to spontaneously undergo noncoordinate phase variation between ON and OFF expression states. The high rate of Vsp phenotypic switching was also shown to be linked with DNA rearrangements that occur at high frequency in the M. bovis chromosome (I. Lysnyansky, R. Rosengarten, and D. Yogev, J. Bacteriol. 178:5395–5401, 1996). In the present study, 13 single-copyvsp genes organized in a chromosomal cluster were identified and characterized. All vsp genes encode highly conserved N-terminal domains for membrane insertion and lipoprotein processing but divergent mature Vsp proteins. About 80% of eachvsp coding region is composed of reiterated coding sequences that create a periodic polypeptide structure. Eighteen distinct repetitive domains of different lengths and amino acid sequences are distributed within the products of the variousvsp genes that are subject to size variation due to spontaneous insertions or deletions of these periodic units. Some of these repeats were found to be present in only one Vsp family member, whereas other repeats recurred at variable locations in several Vsps. Each vsp gene is also 5′ linked to a highly homologous upstream region composed of two internal cassettes. The findings that rearrangement events are associated with Vsp phenotypic switching and that multiple regions of high sequence similarity are present upstream of the vsp genes and within the vsp coding regions suggest that modulation of the Vsp antigenic repertoire is determined by recombination processes that occur at a high frequency within the vsp locus of M. bovis.

Sign in / Sign up

Export Citation Format

Share Document