FT-IR spectroscopic investigation of bacterial cell envelopes from Zymomonas mobilis which have different surface hydrophobicities

Abstract

Changes in the cell envelope composition of bacteria Zymomonas mobilis 113S which resulted in varied cell surface hydrophobicity (CSH) were examined using FT-IR-spectroscopy and conventional methods of biochemical analysis. Significant differences in all analyses were detected between hydrophilic and hydrophobic compounds in the envelopes of Z. mobilis. A significant positive linear relationship (P<0.01) was observed between CSH values of Z. mobilis and the ratio of absorbance band intensities assigned to the CH2 and CH3 vibrations from lipids as well as the asymmetric and symmetric stretching vibrations of these methylene and methyl groups. Differences were also seen between the ratio of band absorbances arising from Amide I and Amide II. In addition, the ratio of absorbance intensities assigned to carbohydrates was found to correlate with the CSH of Z. mobilis. Furthermore, a significant inverse relationship (P<0.01) was detected between CSH of Z. mobilis and the band position (frequency) shift of asymmetric and symmetric stretching of methylene groups, alkyl esters (>CO str) and Amide I, as well as a positive linear relationship (P<0.05) between the band position shift of Amide II and carbohydrates and CSH of Z. mobilis. Qualitative and quantitative composition of the cell envelopes was found to correlate with both the CSH of Z. mobilis and the spectral data. The observed multiple correlations between the concentration of proteins, carbohydrates and lipids of cell envelopes and selected indices of FT-IR spectra indicate the complex relationship of Z. mobilis cell envelope constituents. The results of present study suggest that FT-IR spectroscopy can be used as a convenient method to evaluate the properties of cell envelopes from Gram-negative bacteria.