Date of Award

Spring 2001

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Wayne L. Hynes

Committee Member

Keith A. Carson

Committee Member

Christopher Osgood

Call Number for Print

Special Collections LD4331.B46 Q56 2001


The lantibiotic SA-FF22, produced by Streptococcus pyogenes strain FF22, was the first described antimicrobial peptide produced by a Streptococcus species. S. pyogenes is a group A Streptococcus responsible for such human illness as strep-throat, rheumatic fever, necrotizing fasciitis, endocarditis, and meningitis. Previous studies of SA-FF22 have shown that antimicrobial activity is lost in the presence of lmM magnesium. We hypothesize that the lack of SA-FF22 activity in the presence of magnesium is due to an absence of transcription of scnA, the gene encoding SA-FF22. The lack of transcriptional activation of scnA may be due to an absence of ScnR, a putative transcriptional activator of scnA. To examine this hypothesis, individual reporter constructs were made to assay the transcriptional activation of scnR and scnA in the presence and absence of magnesium. The firefly luciferase gene (luc) was used as a reporter by placing it downstream of the putative scnA or scnR promoters. These constructs were subsequently integrated into the chromosome of S. pyogenes strain FF22. Luciferase production was measured as an indication of transcription from the putative scnA or scnR promoters. Luciferase assay results indicate that scnA transcription is slightly increa5'ed by magnesium levels ≤10mM, and abolished at levels of 15mM magnesium. Our inhibition studies indicate that SA-FF22 activity is present, but slightly reduced, at magnesium levels ~5mM. This suggests that inhibition of SA-FF22 in the presence of magnesium is not occurring at the transcriptional level as was originally hypothesized. These results indicate that the absence of SA-FF22 activity in the presence of magnesium (>5mM) is occurring at a post-transcriptional stage of SA-FF22production.


In Copyright. URI: This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).