Identification and characterization of pigmented photoreceptor-producing microorganisms using FTIR spectroscopy

The identification, differentiation and classification of microorganisms have been subjects of research for many years. Recently, Fourier transform infrared (FTIR) spectroscopy techniques have gained attention in the characterization and classification of microorganisms based on biochemical profiles and cell structure characteristics. In the present study, the characterization and differentiation of pigmented photoreceptor-producing microorganisms using FTIR spectroscopy was carried out. For this purpose some microorganisms were isolated from different environments, of which three photoreceptor-producing bacteria were selected to limit the scope of the study to one phenotypic characteristic. Genomic relatedness among the isolated strains was investigated and it was shown that these strains had similarities to the Kushneria marisflavi, Halobacillus halophilus and Halobacillus faecis species. In addition, Halobacterium salinarum was investigated as a typical representative photoreceptor-producing archaeon. Spectra (500-4000 cm-1) of the intact cells and crude extracted pigments were recorded on an FTIR spectrometer and compared with each other. The similarities among the spectra were evaluated using hierarchical cluster analysis and compared with the phylogenic tree based on genomic study. Our results demonstrate that hierarchical clustering based on extracted pigments shows separation of strains more distinctly than those based on intact cells. The results of the present study suggest that FTIR analysis of bacterial pigments is an easy and economical technique comparable to other phylogenetic markers, for the differentiation and characterization of bacteria.