scholarly journals Genome of the Opportunistic Pathogen Streptococcus sanguinis

2007 ◽  
Vol 189 (8) ◽  
pp. 3166-3175 ◽  
Author(s):  
Ping Xu ◽  
Joao M. Alves ◽  
Todd Kitten ◽  
Arunsri Brown ◽  
Zhenming Chen ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Opportunistic Pathogen ◽  
Surface Proteins ◽  
The Other ◽  
Vitamin B ◽  
Circular Dna ◽  
Streptococcus Sanguinis ◽  
Dna Molecule ◽  
Neutropenic Patients

ABSTRACT The genome of Streptococcus sanguinis is a circular DNA molecule consisting of 2,388,435 bp and is 177 to 590 kb larger than the other 21 streptococcal genomes that have been sequenced. The G+C content of the S. sanguinis genome is 43.4%, which is considerably higher than the G+C contents of other streptococci. The genome encodes 2,274 predicted proteins, 61 tRNAs, and four rRNA operons. A 70-kb region encoding pathways for vitamin B12 biosynthesis and degradation of ethanolamine and propanediol was apparently acquired by horizontal gene transfer. The gene complement suggests new hypotheses for the pathogenesis and virulence of S. sanguinis and differs from the gene complements of other pathogenic and nonpathogenic streptococci. In particular, S. sanguinis possesses a remarkable abundance of putative surface proteins, which may permit it to be a primary colonizer of the oral cavity and agent of streptococcal endocarditis and infection in neutropenic patients.

scholarly journals Inducible Macrolide Resistance inCorynebacterium jeikeium

2001 ◽  
Vol 45 (7) ◽  
pp. 1982-1989 ◽  
Author(s):  
Adriana E. Rosato ◽  
Bonnie S. Lee ◽  
Kevin A. Nash
Keyword(s):  
Drug Resistance ◽  
Resistance Genes ◽  
Broad Spectrum ◽  
Antimicrobial Agents ◽  
Opportunistic Pathogen ◽  
Macrolide Resistance ◽  
The Other ◽  
Broad Spectrum Resistance ◽  
Neutropenic Patients ◽  
Group 3

ABSTRACT Corynebacterium jeikeium is an opportunistic pathogen primarily of immunocompromised (neutropenic) patients. Broad-spectrum resistance to antimicrobial agents is a common feature of C. jeikeium clinical isolates. We studied the profiles of susceptibility of 20 clinical strains of C. jeikeium to a range of antimicrobial agents. The strains were separated into two groups depending on the susceptibility to erythromycin (ERY), with one group (17 strains) representing resistant organisms (MIC > 128 μg/ml) and the second group (3 strains) representing susceptible organisms (MIC ≤ 0.25 μg/ml). The ERY resistance crossed to other members of the macrolide-lincosamide-streptogramin B (MLSb) group. Furthermore, this resistance was inducible with MLSb agents but not non-MLSb agents. Expression of ERY resistance was linked to the presence of an allele of the class X erm genes,erm(X)cj, with >93% identity to other ermgenes of this class. Our evidence indicates that erm(X)cj is integrated within the chromosome, which contrasts with previous reports for the plasmid-associated erm(X) genes found inC. diphtheriae and C. xerosis. In 40% ofC. jeikeium strains, erm(X)cj is present within the transposon, Tn5432. However, in the remaining strains, the components of Tn5432 (i.e., the erm and transposase genes) have separated within the chromosome. The rearrangement of Tn5432 leads to the possibility that the other drug resistance genes have become included in a new composite transposon bound by the IS1249 elements.

scholarly journals Identification of the Pseudomonas aeruginosa O17 and O15 O-Specific Antigen Biosynthesis Loci Reveals an ABC Transporter-Dependent Synthesis Pathway and Mechanisms of Genetic Diversity

2020 ◽  
Vol 202 (19) ◽  
Author(s):  
Steven M. Huszczynski ◽  
Youai Hao ◽  
Joseph S. Lam ◽  
Cezar M. Khursigara
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Abc Transporter ◽  
Specific Antigen ◽  
Opportunistic Pathogen ◽  
Content Type ◽  
O Antigen ◽  
O Antigens ◽  
Dependent Pathway

ABSTRACT Many bacterial cell surface glycans, such as the O antigen component of lipopolysaccharide (LPS), are produced via the so-called Wzx/Wzy- or ABC transporter-dependent pathways. O antigens are highly diverse polysaccharides that protect bacteria from their environment and engage in important host-pathogen interactions. The specific structure and composition of O antigens are the basis of classifying bacteria into O serotypes. In the opportunistic pathogen Pseudomonas aeruginosa, there are currently 20 known O-specific antigen (OSA) structures. The clusters of genes responsible for 18 of these O antigens have been identified, all of which follow the Wzx/Wzy-dependent pathway and are located at a common locus. In this study, we located the two unidentified O antigen biosynthesis clusters responsible for the synthesis of the O15 and the O17 OSA structures by analyzing published whole-genome sequence data. Intriguingly, these clusters were found outside the conserved OSA biosynthesis locus and were likely acquired through multiple horizontal gene transfer events. Based on data from knockout and overexpression studies, we determined that the synthesis of these O antigens follows an ABC transporter-dependent rather than a Wzx/Wzy-dependent pathway. In addition, we collected evidence to show that the O15 and O17 polysaccharide chain lengths are regulated by molecular rulers with distinct and variable domain architectures. The findings in this report are critical for a comprehensive understanding of O antigen biosynthesis in P. aeruginosa and provide a framework for future studies. IMPORTANCE P. aeruginosa is a problematic opportunistic pathogen that causes diseases in those with compromised host defenses, such as those suffering from cystic fibrosis. This bacterium produces a number of virulence factors, including a serotype-specific O antigen. Here, we identified and characterized the gene clusters that produce the O15 and O17 O antigens and show that they utilize a pathway for synthesis that is distinct from that of the 18 other known serotypes. We also provide evidence that these clusters have acquired mutations in specific biosynthesis genes and have undergone extensive horizontal gene transfer within the P. aeruginosa population. These findings expand on our understanding of O antigen biosynthesis in Gram-negative bacteria and the mechanisms that drive O antigen diversity.

scholarly journals CRISPR-Cas systems restrict horizontal gene transfer in Pseudomonas aeruginosa

2020 ◽  
Author(s):  
Rachel M. Wheatley ◽  
R. Craig MacLean
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Gc Content ◽  
Adaptive Immune System ◽  
Opportunistic Pathogen ◽  
Adaptive Immune ◽  
Foreign Dna ◽  
Integrative Conjugative Elements ◽  
Major Target

AbstractCRISPR-Cas systems provide bacteria and archaea with an adaptive immune system that targets foreign DNA. However, the xenogenic nature of immunity provided by CRISPR-Cas raises the possibility that these systems may constrain horizontal gene transfer. Here we test this hypothesis in the opportunistic pathogen Pseudomonas aeruginosa, which has emerged an important model system for understanding CRISPR-Cas function. Across the diversity of P. aeruginosa, active CRISPR-Cas systems are associated with smaller genomes and a reduced GC content, suggesting that CRISPR-Cas inhibits the acquisition of foreign DNA. Although phage are the major target of CRISPR-Cas spacers, more than 80% of isolates with an active CRISPR-Cas system have spacers that target integrative conjugative elements (ICE) or the conserved conjugative transfer machinery used by plasmids and ICE. Consistent with these results, genomes containing active CRISPR-Cas systems harbor a lower abundance of both prophage and ICE. Crucially, spacers in genomes with active CRISPR-Cas systems map to ICE and phage that are integrated into the chromosomes of closely related genomes lacking CRISPR-Cas immunity, providing direct evidence that CRISPR-Cas constrains horizontal gene transfer in these lineages. In conclusion, we find that CRISPR-Cas acts as an important constraint to horizontal gene transfer, suggesting that CRISPR-Cas may constrain the ability of this pathogen to adapt to new niches and stressors.

scholarly journals Primary endosymbiosis: have cyanobacteria and Chlamydiae ever been roommates?

2014 ◽  
Vol 83 (4) ◽  
pp. 291-302 ◽  
Author(s):  
Philippe Deschamps
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Green Algae ◽  
Red Algae ◽  
The Other ◽  
Tripartite Model ◽  
Plant Genomes ◽  
Comparable Level ◽  
Ecological Success ◽  
Primary Endosymbiosis

Eukaryotes acquired the ability to process photosynthesis by engulfing a cyanobacterium and transforming it into a genuine organelle called the plastid. This event, named primary endosymbiosis, occurred once more than a billion years ago, and allowed the emergence of the Archaeplastida, a monophyletic supergroup comprising the green algae and plants, the red algae and the glaucophytes. Of the other known cases of symbiosis between cyanobacteria and eukaryotes, none has achieved a comparable level of cell integration nor reached the same evolutionary and ecological success than primary endosymbiosis did. Reasons for this unique accomplishment are still unknown and difficult to comprehend. The exploration of plant genomes has revealed a considerable amount of genes closely related to homologs of Chlamydiae bacteria, and probably acquired by horizontal gene transfer. Several studies have proposed that these transferred genes, which are mostly involved in the functioning of the plastid, may have helped the settlement of primary endosymbiosis. Some of these studies propose that Chlamydiae and cyanobacterial symbionts coexisted in the eukaryotic host of the primary endosymbiosis, and that Chlamydiae provided solutions for the metabolic symbiosis between the cyanobacterium and the host, ensuring the success of primary endosymbiosis. In this review, I present a reevaluation of the contribution of Chlamydiae genes to the genome of Archaeplastida and discuss the strengths and weaknesses of this tripartite model for primary endosymbiosis.

scholarly journals CRISPR-Cas systems restrict horizontal gene transfer in Pseudomonas aeruginosa

2020 ◽  
Author(s):  
Rachel M. Wheatley ◽  
R. Craig MacLean
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Gc Content ◽  
Adaptive Immune System ◽  
Opportunistic Pathogen ◽  
Evolutionary Mechanisms ◽  
Foreign Dna ◽  
Integrative Conjugative Elements ◽  
Major Target

AbstractCRISPR-Cas systems provide bacteria and archaea with an adaptive immune system that targets foreign DNA. However, the xenogenic nature of immunity provided by CRISPR-Cas raises the possibility that these systems may constrain horizontal gene transfer. Here we test this hypothesis in the opportunistic pathogen Pseudomonas aeruginosa, which has emerged as an important model system for understanding CRISPR-Cas function. Across the diversity of P. aeruginosa, active CRISPR-Cas systems are associated with smaller genomes and higher GC content, suggesting that CRISPR-Cas inhibits the acquisition of foreign DNA. Although phage is the major target of CRISPR-Cas spacers, more than 80% of isolates with an active CRISPR-Cas system have spacers that target integrative conjugative elements (ICE) or the conserved conjugative transfer machinery used by plasmids and ICE. Consistent with these results, genomes containing active CRISPR-Cas systems harbour a lower abundance of both prophage and ICE. Crucially, spacers in genomes with active CRISPR-Cas systems map to ICE and phage that are integrated into the chromosomes of closely related genomes lacking CRISPR-Cas immunity. We propose that CRISPR-Cas acts as an important constraint to horizontal gene transfer, and the evolutionary mechanisms that ensure its maintenance or drive its loss are key to the ability of this pathogen to adapt to new niches and stressors.

scholarly journals The effect of aminoglycosides on horizontal gene transfer in Klebsiella pneumoniae

2020 ◽  
Vol 44 (170) ◽  
pp. 105-120
Author(s):  
Iván Camilo Acosta ◽  
Leonardo Posada ◽  
Mónica Gabriela Huertas ◽  
María Mercedes Zambrano Eder
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Klebsiella Pneumoniae ◽  
Cell Envelope ◽  
Low Frequency ◽  
Opportunistic Pathogen ◽  
Extracellular Dna ◽  
Common Mechanism ◽  
Resistant Bacteria ◽  
Global Risk

Antibiotic-resistant bacteria represent a global risk to public health. Horizontal gene transfer, a common mechanism for genetic exchange in bacteria, plays an essential role in the acquisition of resistance genes. In this work, we evaluated the effect of sub-lethal concentrations of antibiotics on plasmid transfer by conjugation and transformation in the opportunistic pathogen Klebsiella pneumoniae. Despite not being naturally competent, this bacterium could acquire extracellular DNA from various plasmids at a very low frequency, which increased upon incubating cells with the aminoglycoside antibiotics amikacin and gentamicin. Transfer by conjugation analyzed using a clinical isolate carrying plasmid pNDM-1 also increased in the presence of sub-lethal concentrations of antibiotics. An RNAseq analysis showed differential expression of several genes when cells were incubated in the presence of sub-lethal concentrations of amikacin suggesting metabolic and regulatory changes, as well as alteration of cell envelope components that could affect the uptake of foreign DNA. These results suggest that sub-lethal concentrations of some aminoglycosides, in particular amikacin, can promote the transfer of resistance-bearing genetic elements in K. pneumoniae, which is relevant for understanding the spread of resistance determinants in this human pathogen.

scholarly journals Two Distinct Mechanisms Cause Heterogeneity of 16S rRNA

1999 ◽  
Vol 181 (1) ◽  
pp. 78-82 ◽  
Author(s):  
Kumiko Ueda ◽  
Tatsuji Seki ◽  
Takuji Kudo ◽  
Toshiomi Yoshida ◽  
Masakazu Kataoka
Keyword(s):  
Secondary Structure ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
16S Rrna ◽  
Direct Sequencing ◽  
The Other ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Rrna Gene ◽  
The 16S Rrna Gene

ABSTRACT To investigate the frequency of heterogeneity among the multiple 16S rRNA genes within a single microorganism, we determined directly the 120-bp nucleotide sequences containing the hypervariable α region of the 16S rRNA gene from 475 Streptomyces strains. Display of the direct sequencing patterns revealed the existence of 136 heterogeneous loci among a total of 33 strains. The heterogeneous loci were detected only in the stem region designated helix 10. All of the substitutions conserved the relevant secondary structure. The 33 strains were divided into two groups: one group, including 22 strains, had less than two heterogeneous bases; the other group, including 11 strains, had five or more heterogeneous bases. The two groups were different in their combinations of heterogeneous bases. The former mainly contained transitional substitutions, and the latter was mainly composed of transversional substitutions, suggesting that at least two mechanisms, possibly misincorporation during DNA replication and horizontal gene transfer, cause rRNA heterogeneity.

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