@article{TEXTUAL,
      recid = {10448},
      author = {Sun, Fei and Cho, Hoonsik and Jeong, Do-Won and Li,  Chunling and He, Chuan and Bae, Taeok},
      title = {Aureusimines in &amp;lt;i&amp;gt;Staphylococcus aureus&amp;lt;/i&amp;gt;  Are Not Involved in Virulence},
      journal = {PLOS ONE},
      address = {2010-12-29},
      number = {TEXTUAL},
      abstract = {&lt;p&gt;Background: Recently, dipeptide aureusimines were  reported to activate expression of staphylococcal virulence  genes, such as alpha-hemolysin, and increase &lt;em&gt;S.  aureus&lt;/em&gt; virulence. Surprisingly, most of the virulence  genes affected by aureusimines form part of the regulon of  the SaeRS two component system (TCS), raising the  possibility that SaeRS might be directly or indirectly  involved in the aureusimine-dependent signaling  process.&lt;/p&gt;&lt;p&gt;Methodology/Principal Findings: Using HPLC  analyses, we confirmed that a transposon mutant of  &lt;em&gt;ausA&lt;/em&gt;, the gene encoding the aureusimine dipeptide  synthesis enzyme, does not produce dipeptides. However, the  transposon mutant showed normal hemolysis activity and  alpha-hemolysin/SaeP production. Furthermore, the P1  promoter of the &lt;em&gt;sae&lt;/em&gt; operon, one of the targets of  the SaeRS TCS, showed normal transcription activity.  Moreover, in contrast to the original report, the  &lt;em&gt;ausA&lt;/em&gt; transposon mutant did not exhibit attenuated  virulence in an animal infection model. DNA sequencing  revealed that the &lt;em&gt;ausA&lt;/em&gt; deletion mutant used in the  original study has an 83 nt-duplication in &lt;em&gt;saeS&lt;/em&gt;.  Hemolysis activity of the original mutant was restored by a  plasmid carrying the &lt;em&gt;sae&lt;/em&gt; operon. A mutant of the  &lt;em&gt;sae&lt;/em&gt; operon showed elevated resistance to  chloramphenicol and erythromycin, two antibiotics widely  used during staphylococcal mutagenesis. At 43°C in the  presence of erythromycin and aeration, the conditions  typically employed for staphylococcal mutagenesis, an  &lt;em&gt;saeR&lt;/em&gt; transposon mutant grew much faster than a  control mutant and the &lt;em&gt;saeR&lt;/em&gt; mutant was highly  enriched in a mixed culture  experiment.&lt;/p&gt;&lt;p&gt;Conclusions/Significance: Our results  show that the previously reported roles of aureusimines in  staphylococcal gene regulation and virulence were due to an  unintended mutation in &lt;em&gt;saeS&lt;/em&gt;, which was likely  selected due to elevated resistance of the mutant to  environmental stresses. Thus, there is no evidence  indicating that the dipeptide aureusimines play a role in  &lt;em&gt;sae&lt;/em&gt;-mediated virulence factor production or  contribute to staphylococcal virulence.&lt;/p&gt;},
      url = {http://knowledge.uchicago.edu/record/10448},
}