scholarly journals Evolution of an Autotransporter: Domain Shuffling and Lateral Transfer from Pathogenic Haemophilus toNeisseria

2001 ◽  
Vol 183 (15) ◽  
pp. 4626-4635 ◽  
Author(s):  
Jeamelia Davis ◽  
Arnold L. Smith ◽  
William R. Hughes ◽  
Miriam Golomb
Keyword(s):  
Virulence Genes ◽  
Phase Variation ◽  
Laboratory Strain ◽  
Respiratory Pathogens ◽  
Passenger Domain ◽  
Sequence Comparisons ◽  
Base Content ◽  
Surface Molecules ◽  
Unrelated Sequence ◽  
Brazilian Purpuric Fever

ABSTRACT The genomes of pathogenic Haemophilus influenzaestrains are larger than that of Rd KW20 (Rd), the nonpathogenic laboratory strain whose genome has been sequenced. To identify potential virulence genes, we examined genes possessed by Int1, an invasive nonencapsulated isolate from a meningitis patient, but absent from Rd. Int1 was found to have a novel gene termed lav, predicted to encode a member of the AIDA-I/VirG/PerT family of virulence-associated autotransporters (ATs). Associated withlav are multiple repeats of the tetranucleotide GCAA, implicated in translational phase variation of surface molecules. Laterally acquired by H. influenzae, lav is restricted in distribution to a few pathogenic strains, including H. influenzae biotype aegyptius and Brazilian purpuric fever isolates. The DNA sequence of lav is surprisingly similar to that of a gene previously described for Neisseria meningitidis. Sequence comparisons suggest that lavwas transferred relatively recently from Haemophilus toNeisseria, shortly before the divergence of N. meningitidis and Neisseria gonorrhoeae. Segments oflav predicted to encode passenger and β-domains differ sharply in G+C base content, supporting the idea that AT genes have evolved by fusing domains which originated in different genomes. Homology and base sequence comparisons suggest that a novel biotype aegyptius AT arose by swapping an unrelated sequence for the passenger domain of lav. The unusually mobile lav locus joins a growing list of genes transferred from H. influenzae to Neisseria. Frequent gene exchange suggests a common pool of hypervariable contingency genes and may help to explain the origin of invasiveness in certain respiratory pathogens.

scholarly journals A Comparative Genomic Study of Attenuated and Virulent Strains of Babesia bigemina

Pathogens ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 318
Author(s):  
Bernardo Sachman-Ruiz ◽  
Luis Lozano ◽  
José J. Lira ◽  
Grecia Martínez ◽  
Carmen Rojas ◽  
...  
Keyword(s):  
In Vitro Culture ◽  
Virulence Genes ◽  
Laboratory Strain ◽  
Host Cells ◽  
Comparative Genomic ◽  
Local Alignment ◽  
Host Immune System ◽  
Babesia Bigemina ◽  
Genomic Study

Cattle babesiosis is a socio-economically important tick-borne disease caused by Apicomplexa protozoa of the genus Babesia that are obligate intraerythrocytic parasites. The pathogenicity of Babesia parasites for cattle is determined by the interaction with the host immune system and the presence of the parasite’s virulence genes. A Babesia bigemina strain that has been maintained under a microaerophilic stationary phase in in vitro culture conditions for several years in the laboratory lost virulence for the bovine host and the capacity for being transmitted by the tick vector. In this study, we compared the virulome of the in vitro culture attenuated Babesia bigemina strain (S) and the virulent tick transmitted parental Mexican B. bigemina strain (M). Preliminary results obtained by using the Basic Local Alignment Search Tool (BLAST) showed that out of 27 virulence genes described and analyzed in the B. bigemina virulent tick transmitted strain, only five were fully identified in the attenuated laboratory strain. In all cases, the identity and coverture of the identified genes of the wildtype strain were higher than those of the laboratory strain. This finding is putatively associated with the continuous partial loss of virulence genes in the laboratory strain after several passages of the parasite population under optimal in vitro growth conditions. The loss of virulence factors might be reflected in the absence of symptoms of the disease in cattle inoculated with the attenuated strain despite the presence of infection in the bovine host cells.

scholarly journals What a Difference a Gene Makes: Identification of Virulence Factors of Cowpox Virus

2019 ◽  
Vol 94 (2) ◽  
Author(s):  
Aistė Tamošiūnaitė ◽  
Saskia Weber ◽  
Timo Schippers ◽  
Annika Franke ◽  
Zhiyong Xu ◽  
...  
Keyword(s):  
Wistar Rats ◽  
High Throughput Sequencing ◽  
Virulence Genes ◽  
Expression Profiles ◽  
Survival Rates ◽  
Laboratory Strain ◽  
General Interest ◽  
Infection Model ◽  
Cowpox Virus

ABSTRACT Cowpox virus (CPXV) is a zoonotic orthopoxvirus (OPV) that causes spillover infections from its animal hosts to humans. In 2009, several human CPXV cases occurred through transmission from pet rats. An isolate from a diseased rat, RatPox09, exhibited significantly increased virulence in Wistar rats and caused high mortality compared to that caused by the mildly virulent laboratory strain Brighton Red (BR). The RatPox09 genome encodes four genes which are absent in the BR genome. We hypothesized that their gene products could be major factors influencing the high virulence of RatPox09. To address this hypothesis, we employed several BR-RatPox09 chimeric viruses. Using Red-mediated mutagenesis, we generated BR-based knock-in mutants with single or multiple insertions of the respective RatPox09 genes. High-throughput sequencing was used to verify the genomic integrity of all recombinant viruses, and transcriptomic analyses confirmed that the expression profiles of the genes that were adjacent to the modified ones were unaltered. While the in vitro growth kinetics were comparable to those of BR and RatPox09, we discovered that a knock-in BR mutant containing the four RatPox09-specific genes was as virulent as the RatPox09 isolate, causing death in over 75% of infected Wistar rats. Unexpectedly, the insertion of gCPXV0030 (g7tGP) alone into the BR genome resulted in significantly higher clinical scores and lower survival rates matching the rate for rats infected with RatPox09. The insertion of gCPXV0284, encoding the BTB (broad-complex, tramtrack, and bric-à-brac) domain protein D7L, also increased the virulence of BR, while the other two open reading frames failed to rescue virulence independently. In summary, our results confirmed our hypothesis that a relatively small set of four genes can contribute significantly to CPXV virulence in the natural rat animal model. IMPORTANCE With the cessation of vaccination against smallpox and its assumed cross-protectivity against other OPV infections, waning immunity could open up new niches for related poxviruses. Therefore, the identification of virulence mechanisms in CPXV is of general interest. Here, we aimed to identify virulence markers in an experimental rodent CPXV infection model using bacterial artificial chromosome (BAC)-based virus recombineering. We focused our work on the recent zoonotic CPXV isolate RatPox09, which is highly pathogenic in Wistar rats, unlike the avirulent BR reference strain. In several animal studies, we were able to identify a novel set of CPXV virulence genes. Two of the identified virulence genes, encoding a putative BTB/POZ protein (CPXVD7L) and a B22R-family protein (CPXV7tGP), respectively, have not yet been described to be involved in CPXV virulence. Our results also show that single genes can significantly affect virulence, thus facilitating adaptation to other hosts.

scholarly journals Generation of Single-Copy Transposon Insertions in Clostridium perfringens by Electroporation of Phage Mu DNA Transposition Complexes

2009 ◽  
Vol 75 (9) ◽  
pp. 2638-2642 ◽  
Author(s):  
A. Lanckriet ◽  
L. Timbermont ◽  
L. J. Happonen ◽  
M. I. Pajunen ◽  
F. Pasmans ◽  
...  
Keyword(s):  
Clostridium Perfringens ◽  
Large Scale ◽  
Virulence Genes ◽  
Field Isolate ◽  
Laboratory Strain ◽  
Single Copy ◽  
Transposon Mutagenesis ◽  
Insertion Mutant ◽  
Mu Transposition ◽  
Transposon Insertions

ABSTRACT Transposon mutagenesis is a tool that is widely used for the identification of genes involved in the virulence of bacteria. Until now, transposon mutagenesis in Clostridium perfringens has been restricted to the use of Tn916-based methods with laboratory reference strains. This system yields primarily multiple transposon insertions in a single genome, thus compromising its use for the identification of virulence genes. The current study describes a new protocol for transposon mutagenesis in C. perfringens, which is based on the bacteriophage Mu transposition system. The protocol was successfully used to generate a single-insertion mutant library both for a laboratory strain and for a field isolate. Thus, it can be used as a tool in large-scale screening to identify virulence genes of C. perfringens.

scholarly journals Determination of natural versus laboratory human infection with Mayaro virus by molecular analysis

1999 ◽  
Vol 123 (3) ◽  
pp. 511-513 ◽  
Author(s):  
T. JUNT ◽  
J. M. HERAUD ◽  
J. LELARGE ◽  
B. LABEAU ◽  
A. TALARMIN
Keyword(s):  
Clinical Signs ◽  
Laboratory Strain ◽  
Skin Lesions ◽  
Human Infection ◽  
Sequence Comparisons ◽  
Source Of Infection ◽  
Level 3 ◽  
Mayaro Virus

A laboratory worker developed clinical signs of infection with Mayaro virus (Togaviridae), an arbovirus of South and Central America, 6 days after preparation of Mayaro viral antigen and 10 days after a trip to a rain forest. There was no evidence of skin lesions during the antigen preparation, and level 3 containment safety measures were followed. Therefore, molecular characterization of the virus was undertaken to identify the source of infection. RT–PCR and DNA sequence comparisons proved the infection was with the laboratory strain. Airborne Mayaro virus contamination is thus a hazard to laboratory personnel.

scholarly journals Deletion of the Alternative Sigma Factor ςB in Staphylococcus aureus Reveals Its Function as a Global Regulator of Virulence Genes

1998 ◽  
Vol 180 (18) ◽  
pp. 4814-4820 ◽  
Author(s):  
Ines Kullik ◽  
Philipp Giachino ◽  
Thomas Fuchs
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Genes ◽  
Laboratory Strain ◽  
Stationary Growth Phase ◽  
Wild Type ◽  
Global Regulator ◽  
Stationary Growth ◽  
Defective Mutant ◽  
Increased Sensitivity ◽  
Type Strains

ABSTRACT A deletion of the sigB operon was constructed in three genetically distinct Staphylococcus aureus strains, and the phenotypes of the resulting mutants were analyzed. Compared to the corresponding wild-type strains, the ΔsigB mutants showed reduced pigmentation, accelerated sedimentation, and increased sensitivity to hydrogen peroxide during the stationary growth phase. A cytoplasmic protein missing in the ΔsigB mutants was identified as alkaline shock protein 23, and an extracellular protein excreted at higher levels in one of the ΔsigB mutants was identified as staphylococcal thermonuclease. Interestingly, mostsigB deletion phenotypes were only seen in S. aureus COL and Newman and not in 8325, which was found to contain an 11-bp deletion in the regulator gene rsbU. Taken together, our results show that ςB is a global regulator which modulates the expression of several virulence factors in S. aureus and that laboratory strain 8325 is a ςB-defective mutant.

scholarly journals Identification of the Site-Specific DNA Invertase Responsible for the Phase Variation of SusC/SusD Family Outer Membrane Proteins in Bacteroides fragilis

2009 ◽  
Vol 191 (19) ◽  
pp. 6003-6011 ◽  
Author(s):  
Haruyuki Nakayama-Imaohji ◽  
Hideki Hirakawa ◽  
Minoru Ichimura ◽  
Shin Wakimoto ◽  
Satoru Kuhara ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Bacteroides Fragilis ◽  
Phase Variation ◽  
Gene Clusters ◽  
Site Specific ◽  
E Coli ◽  
Surface Molecules ◽  
Gut Microbe

ABSTRACT The human gut microbe Bacteroides fragilis can alter the expression of its surface molecules, such as capsular polysaccharides and SusC/SusD family outer membrane proteins, through reversible DNA inversions. We demonstrate here that DNA inversions at 12 invertible regions, including three gene clusters for SusC/SusD family proteins, were controlled by a single tyrosine site-specific recombinase (Tsr0667) encoded by BF0667 in B. fragilis strain YCH46. Genetic disruption of BF0667 diminished or attenuated shufflon-type DNA inversions at all three susC/susD genes clusters, as well as simple DNA inversions at nine other loci, most of which colocalized with susC/susD family genes. The inverted repeat sequences found within the Tsr0667-regulated invertible regions shared the consensus motif sequence AGTYYYN4GDACT. Tsr0667 specifically mediated the DNA inversions of 10 of the 12 regions, even under an Escherichia coli background when the invertible regions were exposed to BF0667 in E. coli cells. Thus, Tsr0667 is an additional globally acting DNA invertase in B. fragilis, which probably involves the selective expression of SusC/SusD family outer membrane proteins.

scholarly journals Analysis of potential virulence genes and competence to transformation in Haemophilus influenzae biotype aegyptius associated with Brazilian Purpuric Fever

2021 ◽  
Vol 44 (1) ◽  
Author(s):  
Rafaella Fabiana Carneiro Pereira ◽  
Thais Holtz Theizen ◽  
Daisy Machado ◽  
João Paulo de Oliveira Guarnieri ◽  
Gabriel Piccirillo Gomide ◽  
...  
Keyword(s):  
Haemophilus Influenzae ◽  
Virulence Genes ◽  
Brazilian Purpuric Fever

scholarly journals Bacteriophage HP2 of Haemophilus influenzae

2002 ◽  
Vol 184 (24) ◽  
pp. 6893-6905 ◽  
Author(s):  
Bryan J. Williams ◽  
Miriam Golomb ◽  
Thomas Phillips ◽  
Joshua Brownlee ◽  
Maynard V. Olson ◽  
...  
Keyword(s):  
Haemophilus Influenzae ◽  
Host Range ◽  
Chromosomal Evolution ◽  
Respiratory Pathogens ◽  
Diverse Group ◽  
Novel Genes ◽  
Sequence Comparisons ◽  
Host Chromosome ◽  
Genetic Organization ◽  
New Genes

ABSTRACT Temperate bacteriophages effect chromosomal evolution of their bacterial hosts, mediating rearrangements and the acquisition of novel genes from other taxa. Although the Haemophilus influenzae genome shows evidence of past phage-mediated lateral transfer, the phages presumed responsible have not been identified. To date, six different H. influenzae phages are known; of these, only the HP1/S2 group, which lyosogenizes exclusively Rd strains (which were originally encapsulated serotype d), is well characterized. Phages in this group are genetically very similar, with a highly conserved set of genes. Because the majority of H. influenzae strains are nonencapsulated (nontypeable), it is important to characterize phages infecting this larger, genetically more diverse group of respiratory pathogens. We have identified and sequenced HP2, a bacteriophage of nontypeable H. influenzae. Although related to the fully sequenced HP1 (and even more so to the partially sequenced S2) and similar in genetic organization, HP2 has a few novel genes and differs in host range; HP2 will not infect or lysogenize Rd strains. Genomic comparisons between HP1/S2 and HP2 suggest recent divergence, with new genes completely replacing old ones at certain loci. Sequence comparisons suggest that H. influenzae phages evolve by recombinational exchange of genes with each other, with cryptic prophages, and with the host chromosome.

scholarly journals Reservoir of Bacterial Exotoxin Genes in the Environment

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Veronica Casas ◽  
Joseph Magbanua ◽  
Gerico Sobrepeña ◽  
Scott T. Kelley ◽  
Stanley R. Maloy
Keyword(s):  
Staphylococcus Aureus ◽  
Dna Sequence ◽  
Virulence Factors ◽  
Genetic Information ◽  
Virulence Genes ◽  
Environmental Isolate ◽  
Bacterial Isolates ◽  
Bacterial Host ◽  
Sequence Comparisons ◽  
Environmental Reservoir

Many bacteria produce secreted virulence factors called exotoxins. Exotoxins are often encoded by mobile genetic elements, including bacteriophage (phage). Phage can transfer genetic information to the bacteria they infect. When a phage transfers virulence genes to an avirulent bacterium, the bacterium can acquire the ability to cause disease. It is important to understand the role played by the phage that carry these genes in the evolution of pathogens. This is the first report of an environmental reservoir of a bacterial exotoxin gene in an atypical host. Screening bacterial isolates from the environment via PCR identified an isolate with a DNA sequence >95% identical to theStaphylococcus aureusenterotoxin A gene (sea). 16S DNA sequence comparisons and growth studies identified the environmental isolate as a psychrophilicPseudomonasspp. The results indicate that theseagene is present in an alternative bacterial host, providing the first evidence for an environmental pool of exotoxin genes in bacteria.

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