Investigating the Conservation of BamA in Gram-Negative Bacteria

Abstract

Gram-negative bacteria, such as Escherichia coli, have a strong outer membrane (OM) permeability barrier which prevents antibiotics from reaching intracellular targets. This barrier contributes to the lack of antibiotics that target Gram-negative bacteria. However, a new approach to develop drugs against this class of microbes is to target BamA, a surface-exposed protein and an essential part of the BAM complex, which bypasses the need to penetrate the OM. Previous experimental work has identified functionally important parts of BamA such as β1 strand, β16 strand, extracellular loop 6 (eL6), and amino acids E470, A499, A496, F494, G655, G771, and E373. This thesis aimed to analyze the conservation of these important segments of BamA in 42 species of proteobacteria, a major phylum of Gram-negative bacteria, by using a multiple sequence alignment. Additionally, this study investigated the evolutionary pressure on BamA in clinical isolates and environmental isolates of E. coli and Salmonella. The results show that some proteobacteria species and classes have different BamA sequences in comparison to that of E. coli. Finally, BamA is shown to be highly conserved in clinical and environmental isolates and did not mutate due to evolutionary pressure. Further understanding of BamA function and conservation can offer effective new targets for the development of novel antibiotics against Gram-negative bacteria.