Characterization of the LH complexes from a new thermophilic purple bacterium Allochromatium tepidum

T. Kawakamia, N. Nakamuraa, Y. Kimurab, K. Okazakia, A. Ohkoshia, M. T. Madiganc, Z.-Y. Wang-Otomoa
aFaculty of Science, Ibaraki University, Japan; bDepartment of Agrobioscience, Graduate School of Agriculture, Kobe University, Kobe 657-8501, Japan; cDepartment of Microbiology, Southern Illinois University, Carbondale, IL 62901 USA

Allochromatium (A.) tepidum is a new species of thermophilic purple sulfur bacteria isolated from a sulfidic New Zealand microbial mat[1]. It grows optimally near 45˚C, slightly lower than another thermophilic purple sulfur bacterium Thermochromatium (T.) tepidum, but distinctly higher than the mesophilic bacterium A. vinosum. Unlike T. tepidum, the core antenna complex (LH1) of A. tepidum exhibits an absorption maximum (Qy transition) at 890 nm in the near-infrared region, a feature similar to that of A. vinosum and the majority of purple bacteria.

In this work, we describe isolation and purification processes of the LH1-RC and LH2 complexes from A. tepidum strain NZ. The purified complexes have been characterized using absorption spectra, TOF/MS, SDS-PAGE, reverse-phase HPLC chromatography, differential scanning calorimetry, resonance Raman and ATR-FTIR spectroscopies. Comparisons of the spectroscopic and thermodynamic properties between the three purple sulfur bacteria A. tepidum, T. tepidum and A. vinosum will be presented.


[1] M. T. Madigan, M. Asao, S. Takaichi, J. N. Crespi, J. E. Mayers, M. L. Kempher, “Allochromatium tepidum, a New Thermophilic Purple Sulfur Bacterium” 15th International Symposium on Phototrophic Prokaryotes 2015 (Tübingen Germany), Abstract ID186, pp129.