Featured Research

from universities, journals, and other organizations

The human pathogen Streptococcus pneumonia shields foreign DNA derived from other bacteria to promote genetic diversity and vaccine evasion

Date:
February 14, 2013
Source:
Public Library of Science
Summary:
A new report shows that the human pathogen Streptococcus (S.) pneumoniae (one of the known causes of bacterial pneumonia) has an unusual enzyme that protects foreign DNA taken up during transformation, allowing exchange of pathogenicity islands donated from other pathogenic bacteria.

A new report demonstrates that the human pathogen Streptococcus (S.) pneumoniae (one of the known causes of bacterial pneumonia) possesses an unusual enzyme that protects foreign DNA taken up during transformation, allowing exchange of pathogenicity islands donated from other pathogenic bacteria.

This study, published February 14 in the Open Access journal PLOS Pathogens by researchers from the Laboratory of Microbiology and Molecular Genetics (CNRS-Universitι Paul Sabatier, Toulouse, France), establishes a role for this enzyme in protecting internalized DNA from restriction, and simultaneously shows that S. pneumoniae uses transformation, for example by DNA picked up from other bacterial strains, specifically to promote genome diversification.

Exchange of pathogenicity islands is crucial for pneumococcal virulence, as illustrated by the impressive variability in the polysaccharide capsule, which is usually targeted by current vaccines. Acquisition of different capsule loci, by relying on this genetic transformation, thus allows for vaccine evasion. Natural genetic transformation is thought of as the bacterial equivalent of sexual reproduction, allowing intra- and inter-species genetic exchange. This process, involving uptake of foreign DNA as single-strands (ss) that leads to chromosomal integration, is transient in S. pneumoniae.

Restriction-modification (R-M) systems classically include a restrictase, which protects the host bacteria from attack by bacteriophage via the degradation of only the foreign double-stranded (ds) DNA, and a dsDNA methylase that methylates the host genome, providing self-immunity against this restrictase. Since they degrade only foreign DNA, R-M systems are proposed to antagonize transformation by DNA from other bacteria. The DpnII R-M system investigated in this study is present in around half of pneumococcal isolates tested and also possesses an unusual methylase of ssDNA, DpnA, which is specifically induced during the brief genetic transformation time window.

This study shows that DpnA gene is crucial for the exchange of pathogenicity islands when the foreign DNA is unmethylated (i.e., from a non-DpnII modified DNA donor). By methylating the internalized foreign ssDNA, DpnA protects the chromosome of those transformants that incorporate the foreign pathogenicity islands, such as the capsule locus. In the absence of this unique methylation, the novel transformant chromosomes would be degraded by the DpnII restrictase, thus forbidding the acceptance of the foreign DNA sequences.

The researchers found that the role of DpnA is to protect foreign DNA, allowing pathogenicity island exchange between bacteria. Jean-Pierre Claverys, Principal Investigator and senior author of the paper concludes that "this finding is the first evidence for a mechanism that actively promotes genetic diversity of S. pneumoniae through programmed protection and incorporation of foreign DNA."


Story Source:

The above story is based on materials provided by Public Library of Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. Calum Johnston, Bernard Martin, Chantal Granadel, Patrice Polard, Jean-Pierre Claverys. Programmed Protection of Foreign DNA from Restriction Allows Pathogenicity Island Exchange during Pneumococcal Transformation. PLoS Pathogens, 2013; 9 (2): e1003178 DOI: 10.1371/journal.ppat.1003178

Cite This Page:

Public Library of Science. "The human pathogen Streptococcus pneumonia shields foreign DNA derived from other bacteria to promote genetic diversity and vaccine evasion." ScienceDaily. ScienceDaily, 14 February 2013. <www.sciencedaily.com/releases/2013/02/130214194101.htm>.
Public Library of Science. (2013, February 14). The human pathogen Streptococcus pneumonia shields foreign DNA derived from other bacteria to promote genetic diversity and vaccine evasion. ScienceDaily. Retrieved August 22, 2014 from www.sciencedaily.com/releases/2013/02/130214194101.htm
Public Library of Science. "The human pathogen Streptococcus pneumonia shields foreign DNA derived from other bacteria to promote genetic diversity and vaccine evasion." ScienceDaily. www.sciencedaily.com/releases/2013/02/130214194101.htm (accessed August 22, 2014).

Share This




More Health & Medicine News

Friday, August 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Newsy (Aug. 21, 2014) — An experimental drug used to treat Marburg virus in rhesus monkeys could give new insight into a similar treatment for Ebola. Video provided by Newsy
Powered by NewsLook.com
Two US Ebola Patients Leave Hospital Free of the Disease

Two US Ebola Patients Leave Hospital Free of the Disease

AFP (Aug. 21, 2014) — Two American missionaries who were sickened with Ebola while working in Liberia and were treated with an experimental drug are doing better and have left the hospital, doctors say on August 21, 2014. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
Cadavers, a Teen, and a Medical School Dream

Cadavers, a Teen, and a Medical School Dream

AP (Aug. 21, 2014) — Contains graphic content. He's only 17. But Johntrell Bowles has wanted to be a doctor from a young age, despite the odds against him. He was recently the youngest participant in a cadaver program at the Indiana University NW medical school. (Aug. 21) Video provided by AP
Powered by NewsLook.com
American Ebola Patients Released: What Cured Them?

American Ebola Patients Released: What Cured Them?

Newsy (Aug. 21, 2014) — It's unclear whether the American Ebola patients' recoveries can be attributed to an experimental drug or early detection and good medical care. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins