Characterization of a mutan strain of Rhodovulum sulfidophilum lacking the puf A and pufB genes encoding the polpeptides for the light harvesting complex I (B 870)

RAIGER-IUSTMAN, LAURA .; KERBER, NORMA L; PUCHEU, NORMA L; BORNMANN, MARC J.; KOHLER, SIMON; LABAHN, ANDREAS; TADROS, MONIER H; DREWS, GERHART; GARCIA, AUGUSTO F

Arch. Microbiol.

Springer

Año: 2006 vol. 185 p. 407 - 415

0302-8933

Contradictory results on the effectiveness of energy transfer from the light harvesting complex 2 (LH2) directly to the reaction center (RC) in mutant strains lacking the core light-harvesting complex 1 (LH1) have been obtained with cells of Rhodobacter capsulatus and Rhodobacter sphaeroides. A LH1_ mutant of Rhodovulum sulfidophilum, named rsLRI, was constructed by deletion of the pufBA genes, resulting in a kanamycin resistant photosynthetically positive clone. To restore the wild type phenotype, a complemented strain C2 was constructed by inserting in trans a DNA segment containing the pufBA genes. Light induced FTIR difference spectra indicate that the RC in the rsLRI mutant and in the C2 complemented strains are functionally and structurally identical with those in the wild type strain, demonstrating that the assembly and the function of the RC is not impaired by the LH1 deletion. The photosynthetic growth rate of the rsLRI strain increased with decreasing light intensity. At 50 W m_2 no photosynthetic growth was observed. These results indicate that the light energy harvested by the LH2 complex was not or inefficiently transferred to the RC; thus most of the energy necessary for photosynthetic growth is in the LH1_ strain directly absorbed by the RC. It is supposed that in the mutant strain, RC and LH2 cannot interact in an efficient way