ISOLATION AND CHARACTERISATION OF A NEW DEVELOPED MUTANT STRAIN LACKING ANTENNA LIGHT HARVESTING COMPLEX I (B870 COMPLEX

LAURA J. RAIGER-IUSTMAN; NORMA L. PUCHEU; NORMA L. KERBER; AUGUSTO F. GARCIA

Villa Carlos Paz, Córdoba

Congreso; “XXXVIII Reunión anual de la Sociedad Argentina en investigación en Bioquímica y Biología Molecular; 2002

In the marine photosynthetic bacteria Rhodovulum sulfidophilum, the light is captured by the light-harvesting complex 2 (LH2) and funnelled to the core antenna complex LH1-RC (light harvesting complex 1 – reaction center). The aim of this work is to develop a photosynthetically competent mutant lacking LH1 who is able to transfer light energy from the peripheral light-harvesting complex directly to the reaction center. The mutant was designed specifically to delete only the pufBA genes replacing them by a Kanamicin resistance cassette. The mutation in the bacterial chromosome was analysed with a restriction map and a reversion assay.  We obtained one mutant named M1, which presented a green-brownish colony, whereas the WT was dark red. The absorption spectrum shows that it lacks the 880 nm. peak corresponding to the LH1 complex, and the pigment pattern is different from the WT strain. The duplication time in semiaerobiosis is equal to the WT but under photosynthetic conditions the duplication time is significantly lower, especially at intensities of 42 W per m2 or less. We conclude that in Rhodovulum sulfidophilum, as well as described earlier in Rb. sphaeroides, the LH2- RC energy transfer is possible but is less effective and requires of high light intensities to grow under photosynthetic conditions.