Genetic Competence and Transformation in Oral Streptococci

2001 ◽  
Vol 12 (3) ◽  
pp. 217-243 ◽  
Author(s):  
D.G. Cvitkovitch
Keyword(s):  
Genetic Transformation ◽  
Genetic Information ◽  
Physiological State ◽  
Oral Streptococci ◽  
Dna Uptake ◽  
Genetic Competence ◽  
Gram Positive Bacteria ◽  
Oral Biofilms ◽  
Foreign Dna ◽  
Natural Genetic Transformation

The oral streptococci are normally non-pathogenic residents of the human microflora. There is substantial evidence that these bacteria can, however, act as "genetic reservoirs" and transfer genetic information to transient bacteria as they make their way through the mouth, the principal entry point for a wide variety of bacteria. Examples that are of particular concern include the transfer of antibiotic resistance from oral streptococci to Streptococcus pneumoniae. The mechanisms that are used by oral streptococci to exchange genetic information are not well-understood, although several species are known to enter a physiological state of genetic competence. This state permits them to become capable of natural genetic transformation, facilitating the acquisition of foreign DNA from the external environment. The oral streptococci share many similarities with two closely related Gram-positive bacteria. S. pneumoniae and Bacillus subtilis. In these bacteria, the mechanisms of quorum-sensing, the development of competence, and DNA uptake and integration are well-charaterized. Using this knowledge and the data available in genome databases allowed us to identify putative genes involved in these processes in the oral organism Streptococcus mutans. Models of competence development and genetic transformation in the oral streptococci and strategies to confirm these models are discussed. Future studies of competence in oral biofilms, the natural environment of oral streptococci, will be discussed.

scholarly journals An Unstable Competence-Induced Protein, CoiA, Promotes Processing of Donor DNA after Uptake during Genetic Transformation in Streptococcus pneumoniae

2006 ◽  
Vol 188 (14) ◽  
pp. 5177-5186 ◽  
Author(s):  
Bhushan V. Desai ◽  
Donald A. Morrison
Keyword(s):  
Streptococcus Pneumoniae ◽  
Genetic Transformation ◽  
Transcriptional Activation ◽  
Response Regulator ◽  
Specific Response ◽  
Dna Uptake ◽  
Gram Positive Bacteria ◽  
Specific Alternative ◽  
Natural Genetic Transformation

ABSTRACT Natural genetic transformation in Streptococcus pneumoniae entails transcriptional activation of at least two sets of genes. One set of genes, activated by the competence-specific response regulator ComE, is involved in initiating competence, whereas a second set is activated by the competence-specific alternative sigma factor ComX and functions in DNA uptake and recombination. Here we report an initial characterization of CoiA, a ComX-dependent gene product that is induced during competence and is required for transformation. CoiA is widely conserved among gram-positive bacteria, and in streptococci, the entire coiA locus composed of four genes is conserved. By use of immunoblot assay, we show that, similar to its message, CoiA protein is transient, appearing at 10 min and largely disappearing by 30 min post-competence induction. Using complementation analysis, we establish that coiA is the only gene of this induced locus needed for transformability. We find no indication of CoiA having a role in regulating competence. Finally, using 32P- and 3H-labeled donor DNA, we demonstrate that a coiA mutant can internalize normal amounts of donor DNA compared to the wild-type strain but is unable to process it into viable transformants, suggesting a role for CoiA after DNA uptake, either in DNA processing or recombination.

scholarly journals Direct Visualization of Horizontal Gene Transfer by Transformation in Live Pneumococcal Cells Using Microfluidics

Genes ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 675
Author(s):  
Isabelle Mortier-Barrière ◽  
Patrice Polard ◽  
Nathalie Campo
Keyword(s):  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Expression Profiles ◽  
Physiological State ◽  
Microfluidic System ◽  
Live Cells ◽  
Microfluidic Channels ◽  
Dna Uptake ◽  
Fluorescent Reporters ◽  
Natural Genetic Transformation

Natural genetic transformation is a programmed mechanism of horizontal gene transfer in bacteria. It requires the development of competence, a specialized physiological state during which proteins involved in DNA uptake and chromosomal integration are produced. In Streptococcus pneumoniae, competence is transient. It is controlled by a secreted peptide pheromone, the competence-stimulating peptide (CSP) that triggers the sequential transcription of two sets of genes termed early and late competence genes, respectively. Here, we used a microfluidic system with fluorescence microscopy to monitor pneumococcal competence development and transformation, in live cells at the single cell level. We present the conditions to grow this microaerophilic bacterium under continuous flow, with a similar doubling time as in batch liquid culture. We show that perfusion of CSP in the microfluidic chamber results in the same reduction of the growth rate of individual cells as observed in competent pneumococcal cultures. We also describe newly designed fluorescent reporters to distinguish the expression of competence genes with temporally distinct expression profiles. Finally, we exploit the microfluidic technology to inject both CSP and transforming DNA in the microfluidic channels and perform near real time-tracking of transformation in live cells. We show that this approach is well suited to investigating the onset of pneumococcal competence together with the appearance and the fate of transformants in individual cells.

scholarly journals Pseudomonas stutzeri Has Two Closely RelatedpilA Genes (Type IV Pilus Structural Protein) with Opposite Influences on Natural Genetic Transformation

2001 ◽  
Vol 183 (7) ◽  
pp. 2359-2366 ◽  
Author(s):  
Stefan Graupner ◽  
Wilfried Wackernagel
Keyword(s):  
Genetic Transformation ◽  
Pseudomonas Stutzeri ◽  
Leader Peptide ◽  
Duplex Dna ◽  
Dna Uptake ◽  
Structural Protein ◽  
Dichelobacter Nodosus ◽  
Type Iv ◽  
Insertional Inactivation ◽  
Natural Genetic Transformation

ABSTRACT Pseudomonas stutzeri has type IV pili for which the pilA gene (here termed pilAI) provides the structural protein and which are required for DNA uptake and natural genetic transformation. Downstream of pilAIwe identified a gene, termed pilAII, coding for a deduced protein with a size similar to that of PilAI with 55% amino acid sequence identity and with a typical leader peptide including a leader peptidase cleavage site. Fusions to lacZ revealed that pilAII is expressed only about 10% compared topilAI, although the genes are cotranscribed as shown by reverse transcription-PCR. Surprisingly, insertional inactivation ofpilAII produced a hypertransformation phenotype giving about 16-fold-increased transformation frequencies. Hypertransformation also occurred in pilAI pilAII double mutants expressing heterologous pilA genes of nontransformable bacteria, like Pseudomonas aeruginosa or Dichelobacter nodosus. The overexpression of pilAII decreased transformation up to 5,000-fold compared to that of thepilAII mutant. However, neither inactivation ofpilAII nor its overexpression affected the amounts of [3H]thymidine-labeled DNA that were competence-specifically bound and taken up by the cells. In thepilAII mutant, the transformation by purified single-stranded DNA (which depends on comA andexbB, as does transformation by duplex DNA) was also increased 17-fold. It is concluded that PilAII suppresses a step in transformation after the uptake of duplex DNA into the cell and perhaps before its translocation into the cytoplasm. The idea that the degree of the transformability of cells could be permanently adjusted by the expression level of an antagonistic protein is discussed.

scholarly journals An Effective Strategy, Applicable toStreptococcus salivarius and Related Bacteria, To Enhance or Confer Electroporation Competence

1999 ◽  
Vol 65 (9) ◽  
pp. 3800-3804 ◽  
Author(s):  
Nicole D. Buckley ◽  
Christian Vadeboncoeur ◽  
Donald J. LeBlanc ◽  
Linda N. Lee ◽  
Michel Frenette
Keyword(s):  
Cell Concentration ◽  
Oral Streptococci ◽  
Strain Atcc ◽  
Effective Strategy ◽  
Streptococcus Salivarius ◽  
Gram Positive Bacteria ◽  
Wide Range ◽  
Series Of Experiments ◽  
Foreign Dna ◽  
Fresh Isolate

ABSTRACT Despite the large number of techniques available for transformation of bacteria, certain species and strains are still resistant to introduction of foreign DNA. Some oral streptococci are among the organisms that can be particularly difficult to transform. We performed a series of experiments that involved manipulation of growth and recovery media and cell wall weakening, in which the electroporation conditions, cell concentration, and type and concentration of the transforming plasmid were varied. The variables were optimized such that a previously untransformable Streptococcus salivariusstrain, ATCC 25975, could be transformed reproducibly at a level of 105 transformants per μg of DNA. The technique was used to introduce a plasmid into other strains of S. salivarius, including a fresh isolate. Moreover, the same technique was applied successfully to a wide range of oral streptococci and other gram-positive bacteria.

scholarly journals Properties and Biological Role of Streptococcal Fratricins

2012 ◽  
Vol 78 (10) ◽  
pp. 3515-3522 ◽  
Author(s):  
Kari Helene Berg ◽  
Truls Johan Biørnstad ◽  
Ola Johnsborg ◽  
Leiv Sigve Håvarstein
Keyword(s):  
Cell Wall ◽  
Genetic Transformation ◽  
Natural Transformation ◽  
Current View ◽  
Dna Uptake ◽  
Cell Wall Degrading Enzymes ◽  
Content Type ◽  
Streptococcal Species ◽  
Natural Genetic Transformation

ABSTRACTCompetence for natural genetic transformation is widespread in the genusStreptococcus. The current view is that all streptococcal species possess this property. In addition to the proteins required for DNA uptake and recombination, competent streptococci secrete muralytic enzymes termed fratricins. Since the synthesis and secretion of these cell wall-degrading enzymes are always coupled to competence development in streptococci, fratricins are believed to carry out an important function associated with natural transformation. This minireview summarizes what is known about the properties of fratricins and discusses their possible biological roles in streptococcal transformation.

scholarly journals Steady at the wheel: conservative sex and the benefits of bacterial transformation

2016 ◽  
Author(s):  
Ole Herman Ambur ◽  
Jan Engelstädter ◽  
Pål J. Johnsen ◽  
Eric L. Miller ◽  
Daniel E. Rozen
Keyword(s):  
Genetic Transformation ◽  
Large Body ◽  
Theoretical Studies ◽  
Bacterial Cells ◽  
Bacterial Transformation ◽  
Bacterial Populations ◽  
Direct Benefits ◽  
Foreign Dna ◽  
Genomic Conservation ◽  
Natural Genetic Transformation

SummaryMany bacteria are highly sexual, but the reasons for their promiscuity remain obscure. Did bacterial sex evolve to maximize diversity and facilitate adaptation in a changing world, or does it instead help to retain the bacterial functions that work right now? In other words, is bacterial sex innovative or conservative? Our aim in this review is to integrate experimental, bioinformatic and theoretical studies to critically evaluate these alternatives, with a main focus on natural genetic transformation, the bacterial equivalent of eukaryotic sexual reproduction. First, we provide a general overview of several hypotheses that have been put forward to explain the evolution of transformation. Next, we synthesize a large body of evidence highlighting the numerous passive and active barriers to transformation that have evolved to protect bacteria from foreign DNA, thereby increasing the likelihood that transformation takes place among clonemates. Our critical review of the existing literature provides support for the view that bacterial transformation is maintained as a means of genomic conservation that provides direct benefits to both individual bacterial cells and to transformable bacterial populations. We examine the generality of this view across bacteria and contrast this explanation with the different evolutionary roles proposed to maintain sex in eukaryotes.

Sperm cells as vectors for introducing foreign DNA into eggs: Genetic transformation of mice

Cell ◽  
1989 ◽  
Vol 57 (5) ◽  
pp. 717-723 ◽  
Author(s):  
Marialuisa Lavitrano ◽  
Antonella Camaioni ◽  
Vito M. Fazio ◽  
Susanna Dolci ◽  
Maria G. Farace ◽  
...  
Keyword(s):  
Genetic Transformation ◽  
Sperm Cells ◽  
Foreign Dna

scholarly journals Streptococcal Antagonism in Oral Biofilms: Streptococcus sanguinis and Streptococcus gordonii Interference with Streptococcus mutans

2008 ◽  
Vol 190 (13) ◽  
pp. 4632-4640 ◽  
Author(s):  
Jens Kreth ◽  
Yongshu Zhang ◽  
Mark C. Herzberg
Keyword(s):  
Streptococcus Mutans ◽  
Bacterial Species ◽  
Ecological Factors ◽  
Oral Streptococci ◽  
Streptococcus Gordonii ◽  
Interspecies Interactions ◽  
Streptococcus Sanguinis ◽  
Production Of Hydrogen ◽  
Oral Biofilms ◽  
Competence System

ABSTRACT Biofilms are polymicrobial, with diverse bacterial species competing for limited space and nutrients. Under healthy conditions, the different species in biofilms maintain an ecological balance. This balance can be disturbed by environmental factors and interspecies interactions. These perturbations can enable dominant growth of certain species, leading to disease. To model clinically relevant interspecies antagonism, we studied three well-characterized and closely related oral species, Streptococcus gordonii, Streptococcus sanguinis, and cariogenic Streptococcus mutans. S. sanguinis and S. gordonii used oxygen availability and the differential production of hydrogen peroxide (H2O2) to compete effectively against S. mutans. Interspecies antagonism was influenced by glucose with reduced production of H2O2. Furthermore, aerobic conditions stimulated the competence system and the expression of the bacteriocin mutacin IV of S. mutans, as well as the H2O2-dependent release of heterologous DNA from mixed cultures of S. sanguinis and S. gordonii. These data provide new insights into ecological factors that determine the outcome of competition between pioneer colonizing oral streptococci and the survival mechanisms of S. mutans in the oral biofilm.

scholarly journals Methyltransferase DnmA is responsible for genome-wide N6-methyladenosine modifications at non-palindromic recognition sites in Bacillus subtilis

2020 ◽  
Vol 48 (10) ◽  
pp. 5332-5348
Author(s):  
Taylor M Nye ◽  
Lieke A van Gijtenbeek ◽  
Amanda G Stevens ◽  
Jeremy W Schroeder ◽  
Justin R Randall ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Bacillus Subtilis ◽  
Consensus Sequence ◽  
Dna Uptake ◽  
Cellular Functions ◽  
Promoter Regions ◽  
Gram Positive Bacteria ◽  
Genome Wide ◽  
Domains Of Life ◽  
Reporter Assays

Abstract The genomes of organisms from all three domains of life harbor endogenous base modifications in the form of DNA methylation. In bacterial genomes, methylation occurs on adenosine and cytidine residues to include N6-methyladenine (m6A), 5-methylcytosine (m5C), and N4-methylcytosine (m4C). Bacterial DNA methylation has been well characterized in the context of restriction-modification (RM) systems, where methylation regulates DNA incision by the cognate restriction endonuclease. Relative to RM systems less is known about how m6A contributes to the epigenetic regulation of cellular functions in Gram-positive bacteria. Here, we characterize site-specific m6A modifications in the non-palindromic sequence GACGmAG within the genomes of Bacillus subtilis strains. We demonstrate that the yeeA gene is a methyltransferase responsible for the presence of m6A modifications. We show that methylation from YeeA does not function to limit DNA uptake during natural transformation. Instead, we identify a subset of promoters that contain the methylation consensus sequence and show that loss of methylation within promoter regions causes a decrease in reporter expression. Further, we identify a transcriptional repressor that preferentially binds an unmethylated promoter used in the reporter assays. With these results we suggest that m6A modifications in B. subtilis function to promote gene expression.

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