Dr. P.M. Fidopiastis


The role of N-acetylmuramoyl-L-alanine amidase was investigated in Vibrio fischeri ES114, a symbiotic bioluminescent, gram negative microbe. The transposon mutant C10, has a transposon inserted into the gene of interest and was used in this study to characterize role N-acetylmuramoyl-L-alanine amidase in Vibrio fischeri ES114. It is known that the enzyme cleaves the bond between NAM and the first L-alanine in peptidoglycan. The phenotypic effects of the transposon mutation were observed through gram stain, hanging drop, motility assay, biofilm formation, and growth curve. The mutant was observed in chain arrangement with cells measuring 2 μm by 1 μm about twice the size of the wild-type. Furthermore, motility of the mutant was still functional but hindered greatly. An increase in biofilm formation was observed. The increased size of cells and the presence of chain formation suggest that the amidase enzyme is greatly reduced in function causing the mutant to have reduced septation and increased peptidoglycan polymerization. Motility was severely attenuated, due the polar flagella associated with the cell on the end of the chain not being able to produce enough motor rotation to move the whole chain effectively or the sharing of periplasmic space between the cells caused the Na+ concentration to change which led to a defect in the coupling of Na+ flux and the motor rotation. Interestingly the C10 mutant also showed hyper specific luminescence, One possible explanation for this is that due to the large aggregations of cell chains, the microbes’ may be experiencing an artificially high sense of surrounding culture density, and be prematurely expressing their lux genes.


Bacteriology | Biology | Environmental Microbiology and Microbial Ecology | Microbial Physiology | Microbiology