U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Food Safety and Enteric Pathogens Research: Ames, IA
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                People

                    Staff Listing
                                    Careers


        


                    Additional ResourcesSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Midwest Area Ames, Iowa National Animal Disease Center Food Safety and Enteric Pathogens Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            Bearson, Bradley

                                                         - *Brad*item
                                            Casey, Thomasitem
                                            Bearson, Shawn
  Submitted to: American Society for Microbiology
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 2/27/2004
                                    Publication  Date: 5/23/2004
                                    Citation: Bearson, B.L., Casey, T., Bearson, S.M. 2004. Expression of ldrd in E. coli O157:H7 and Salmonella enterica serovar Typhimurium inhibits growth [abstract]. American Society for Microbiology. p. 297.Interpretive Summary:
                                Technical Abstract: Four copies of a toxin-antisense RNA module designated ldr are present in the genome of E. coli K-12.  Expression of ldrD from a multicopy plasmid inhibits cell growth of E. coli (Kawano et al, Mol. Micro. 2002. 45:333).  Homology searches indicate that the ldr modules are present in the genomes of E. coli O157:H7 and Salmonella enterica serovar Typhimurium.  To determine if expression of ldrD inhibits E. coli O157:H7 and S. typhimurium cell growth, the ldrD gene from E. coli O157:H7 was cloned into a plasmid containing an arabinose inducible promoter.  E. coli O157:H7 transformed with the ldrD plasmid followed by plating onto media containing arabinose have a small flat, translucent colony morphology.  S. typhimurium transduced with phage containing the ldrD plasmid do not form visible colonies on inducible media.  Expression of ldrD in E. coli O157:H7 or S. typhimurium also inhibits log-phase cell growth for up to seven hours.  Although the cultures overcome the inhibition following overnight growth, data indicates it is due to loss of the plasmid expressing ldrD.  Furthermore, E. coli O157:H7 containing the ldrD plasmid can be rescued from an inhibited log-phase culture and once again be induced to inhibit cell growth.  Single colony isolation of E. coli O157:H7 containing the ldrD plasmid onto MacConkey arabinose media only formed single colonies in the primary quadrant where growth would usually be confluent.  As LdrD is predicted to be a membrane protein based on topology algorithms, a component of MacConkey media such as bile salts or crystal violet may disrupt the membrane of bacterial cells expressing ldrD.  Recently, chromosome-encoded toxin modules (relBE and mazEF) have been shown to be involved in the regulation of cellular physiology.  As the ldr modules may also regulate aspects of cellular physiology, their cellular role is being investigated.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov