Assessing the effects of adaptive mutations in cusS on motility in Escherichia coli

Student Classification

Naya M. Lewis, 3rd -Year, Biology Zaria A. Ferguson, 3rd -Year, Biology

Faculty Mentor

Dr. Misty Thomas , Department of Biology ; Brittany Sanders Department of Applied Science and Technology

Document Type


Publication Date

Spring 2023


All bacteria including, Escherichia coli, show extreme toxicity to silver, but with use of silver efflux pumps (cusCFBA) low levels of silver can be expelled from the cell. When the bacterial cell is overpowered, it causes a buildup of silver, resulting in cell lysis. E. coli can rapidly develop resistance through adaptive mutations within cusS which is part of a two-component response system with cusR that activates transcription of the cusCFBA efflux pump. As part of the methodology the lab used in vivo recombineering to insert chromosomal mutations into the WT cusS. RNAseq on these mutant strains showed upregulation of flagella genes in presence of silver nitrate. Swarming has been previously correlated with environmental silver as migration may confer an overall fitness advantage. Therefore, our research goal, was to evaluate how adaptive mutations in cusS affected swarming which is the measurable phenotype associated with flagellar genes. For the swarming assay, we used two types of media LB or DMB combined with a low percentage of agar to allow for higher fluidity within the media. After method optimization, we assessed the swarming ability of our four silver resistant cusS mutants and compared it to the WT. Swarming assays showed an increase in swarming for one (T17P) of our cusS mutants on LB media whereas the others showed no changes from the WT. Moving forward, it would be beneficial to image the WT and mutant cells using electron microscopy to visualize and count the number of flagella associated with each cell to better understand the increase in flagella gene expression.

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