Date of Award:
5-1-2004
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Biology
Committee Chair(s)
Jon Y. Takemoto
Committee
Jon Y. Takemoto
Committee
Bart Weimer
Committee
Anne J. Anderson
Committee
Michelle Grilley
Abstract
Many strains of the plant bacterium Pseudomonas syringae produce two major classes of cyclic lipodepsipeptides, the syringomycins and the syringopeptins. Four groups of small cyclic lipodepsipeptides are well known: the syringomycins, syringostatins, syringotoxins, and pseudomycins. They all have antimicrobial activities and tend to be more active against yeasts than against bacteria. The syringopeptins are lesser-known. The best-studied syringopeptins are SP22 and SP25. They possess antibacterial and antifungal activities, but their mechanisms of action and antimicrobial spectra are less studied. Saccharomyces cerevisiae sphingolipid and sterol biosynthetic mutants were used to investigate the mechanism of action of syringopeptins against fungi. Similarly to syringomycin, the growth inhibitory activities of the syringopeptins were less in the mutants as compared to the wild type. It was concluded that sphingolipids and ergosterol play major roles in syringopeptin action against yeast. A new syringopeptin, SP508, isolated from Pseudomonas syringae pv. lachrymans was identified. SP508 represents a new structural variation of the well known SP22 with 22 amino acids residues comprising the peptide moiety. SP508 shows a different antimicrobial activity spectrum than SP22A and was more inhibitory to a bacterium Mycobacterium smegmatis. The minimum inhibitory concentrations of syringopeptins, SP25A, SP22A, SP508, and SP268, were determined for a variety of Gram-positive and Gram-negative bacteria and fungi. It was found that syringopeptins have strong inhibitory activities against Gram-positive bacteria, mycobacterium, and fungi. However, less or no inhibition was observed against Gram-negative bacteria. The mechanism of action against Gram-positive bacteria was investigated by analyzing Bacillus subtilis teichoic acid mutants.
Recommended Citation
Bensaci, Mekki F., "Antimicrobial Activities of Lipodepsipeptide Syringopeptins" (2004). Biology. 694.
https://digitalcommons.usu.edu/etd_biology/694
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