Usefulness of FTIR spectroscopy to distinguish rough and smooth variants of Lactobacillus farciminis CNCM-I-3699
Résumé
In this study, the potential of Fourier transform infrared (FTIR) spectroscopy for assessing putative biochemical and structural differences between the two variants, rough (R) and smooth (S), of Lactobacillus farciminis CNCM-I-3699, a pleomorphic strain, was investigated. The main differences observed were localized in the polysaccharide (1200–900 cm−1) and protein (1700–1500 cm−1) regions. Based on spectral information in these two spectral ranges, clustering resulted in a dendrogram that showed a clear discrimination between both morphotypes. Significant increases in favor of morphotype S compared to R at specific wavenumbers for polysaccharides (22.18% vs. 5.24% at 1068 cm−1) and capsular polysaccharides (16% vs. 13.17% at 1048 cm−1) were recorded. Compared to S, the morphotype R exhibits a 1.27-fold higher signal at the wavenumber of 1637 cm−1 assigned to the amide I β-sheet and a 2.71-fold higher signal at the wavenumber of 1513 cm−1 assigned to the tyrosine involved in the β-sheet arrangement of proteins. The FTIR analysis is efficient to separate and give data on mainly surface component differences observed previously between S colony morphotype (ropy and exopolysaccharide positive) and the R colony morphotype (non-ropy but highly autoaggregative).