Discrimination of E. coli B E BL21(DE3) porin mutants by attenuated total reflectance Fourier-transformed infrared (ATR-FTIR) spectroscopy

Abstract

Attenuated total reflectance Fourier-transformed infrared (ATR-FTIR) spectroscopy measures the changes that occur in a totally internally reflected infrared beam when the evanescent wave it produces penetrates only a few micrometers (0.5-5μm) into the sample, deposited on top of an optically dense crystal (Figure 1) [1]. Both conventional FTIR and ATR-FTIR have been successfully used for bacteria discrimination and classification, as each species presents an unique spectral “fingerprint”, making it a promising, fast and reliable screening method for pathogen identification in a clinic setting [2-3]. In this study, ATR-FTIR is used in an attempt to discriminate between Escherichia (E.) coli BE BL21(DE3) and a derived mutant lacking the major E. coli porins OmpF and OmpC (Table 1). Porins are transmembrane proteins located in the outer membrane of Gram-negative bacteria such as E. coli that allow the passage of various solutes, including antibiotics, playing therefore an important role in the development of antibiotic resistance. The ability to effectively distinguish between strains differing only in the porin profile would mean more than just information on structural differences, but also an initial indication on resistance mechanisms [4]. Strain Relevant genotype