Mekki Bensaci
Utah State University
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Publication
Featured researches published by Mekki Bensaci.
Antimicrobial Agents and Chemotherapy | 2005
Ingeborg Grgurina; Mekki Bensaci; Gabriella Pocsfalvi; Luisa Mannina; Oscar Cruciani; Alberto Fiore; Vincenzo Fogliano; Kevin N. Sorensen; Jon Y. Takemoto
ABSTRACT The syringopeptins are a group of antimicrobial cyclic lipodepsipeptides produced by several plant-associated pseudomonads. A novel syringopeptin, SP508, was shown to be produced as two homologs (A and B) by Pseudomonas syringae pv. lachrymans strain 508 from apple and to structurally resemble syringopeptin SP22. SP508 differed from SP22 and other syringopeptins by having three instead of four α,β-unsaturated amino acids and a longer β-hydroxy acyl chain. Both SP508 and SP22 displayed growth-inhibitory activities against Mycobacterium smegmatis, other gram-positive bacteria, and yeasts but not against gram-negative bacteria. Structure-activity analyses of the SP508 and SP22 homologs indicated chemical structural features that lead to enhanced antimycobacterial activity by these pseudomonad cyclic lipodepsipeptides.
The Journal of Antibiotics | 2010
Cheng-Wei Tom Chang; Marina Y. Fosso; Yukie Kawasaki; Sanjib K. Shrestha; Mekki Bensaci; Jinhua Wang; Conrad K. Evans; Jon Y. Takemoto
Many Actinomycetes aminoglycosides are widely used antibiotics. Although mainly antibacterials, a few known aminoglycosides also inhibit yeasts, protozoans and important crop pathogenic fungal oomycetes. Here we show that attachment of a C8 alkyl chain to ring III of a neamine-based aminoglycoside specifically at the 4″-O position yields a broad-spectrum fungicide (FG08) without the antibacterial properties typical for aminoglycosides. Leaf infection assays and greenhouse studies show that FG08 is capable of suppressing wheat fungal infections by Fusarium graminearum—the causative agent of Fusarium head blight—at concentrations that are minimally phytotoxic. Unlike typical aminoglycoside action of ribosomal protein translation miscoding, FG08s antifungal action involves perturbation of the plasma membrane. This antibacterial to antifungal transformation could pave the way for the development of a new class of aminoglycoside-based fungicides suitable for use in crop disease applications. In addition, this strategy is an example of reviving a clinically obsolete drug by simple chemical modification to yield a new application.
The Journal of Antibiotics | 2009
Jianjun Zhang; Katherine Keller; Jon Y. Takemoto; Mekki Bensaci; Anthony Litke; Przemyslaw Greg Czyryca; Cheng-Wei Tom Chang
A library of 5″-modified neomycin derivatives were synthesized for an antibacterial structure–activity optimization strategy. Two leads exhibited prominent activity against both methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Antibacterial activities were measured when combined with other clinically used antibiotics. Significant synergistic activities were observed, which may lead to the development of novel therapeutic practices in the battle against infectious bacteria.
Frontiers in Microbiology | 2011
Mekki Bensaci; Philip A. Gurnev; Sergey M. Bezrukov; Jon Y. Takemoto
The plant-associated bacterium Pseudomonas syringae pv. syringae simultaneously produces two classes of metabolites: the small cyclic lipodepsinonapeptides such as the syringomycins and the larger cyclic lipodepsipeptide syringopeptins SP22 or SP25. The syringomycins inhibit a broad spectrum of fungi (but particularly yeasts) by lipid-dependent membrane interaction. The syringopeptins are phytotoxic and inhibitory to Gram-positive bacteria. In this study, the fungicidal activities of two major syringopeptins, SP22A and SP25A, and their mechanisms of action were investigated and compared to those of syringomycin E. SP22A and SP25A were observed to inhibit the fungal yeasts Saccharomyces cerevisiae and Candida albicans although less effectively than syringomycin E. S. cerevisiae mutants defective in ergosterol and sphingolipid biosyntheses were less susceptible to SP22A and SP25A but the relative inhibitory capabilities of SRE vs. SP22A and SP25A were maintained. Similar differences were observed for capabilities to cause cellular K+ and Ca2+ fluxes in S. cerevisiae. Interestingly, in phospholipid bilayers the syringopeptins are found to induce larger macroscopic ionic conductances than syringomycin E but form single channels with similar properties. These findings suggest that the syringopeptins target the yeast plasma membrane, and, like syringomycin E, employ a lipid-dependent channel-forming mechanism of action. The differing degrees of growth inhibition by these lipodepsipeptides may be explained by differences in their hydrophobicities. The more hydrophobic SP22A and SP25A might interact more strongly with the yeast cell wall that would create a selective barrier for their incorporation into the plasma membrane.
Journal of Organic Chemistry | 2004
Bryan Elchert; Jie Li; Jinhua Wang; Yu Hui; Ravi Rai; Roger G. Ptak; Priscilla Ward; Jon Y. Takemoto; Mekki Bensaci; Cheng-Wei Tom Chang
Bioorganic & Medicinal Chemistry | 2004
Jinhua Wang; Bryan Elchert; Yu Hui; Jon Y. Takemoto; Mekki Bensaci; John Wennergren; Huiwen Chang; Ravi Rai; Cheng-Wei Tom Chang
ACS Combinatorial Science | 2007
Jianjun Zhang; Hsiao-Nung Chen; Fang-I Chiang; Jon Y. Takemoto; Mekki Bensaci; Cheng-Wei Tom Chang
Archive | 2006
N R Gandhi; Victoria Palmer Skebba; Jon Y. Takemoto; Mekki Bensaci
American Journal of Enology and Viticulture | 2010
Jon Y. Takemoto; Mekki Bensaci; Anthony J. De Lucca; Thomas E. Cleveland; N R Gandhi; Victoria Palmer Skebba
Fems Microbiology Letters | 2007
Mekki Bensaci; Jon Y. Takemoto