Author's School

Graduate School of Arts & Sciences

Author's Department/Program



English (en)

Date of Award

January 2010

Degree Type


Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Robert Blankenship


Photosynthetic organisms have evolved diverse antennas to harvest light of various qualities and intensities. Anoxygenic phototrophs can have bacteriochlorophyll Qy antenna absorption bands ranging from about 700-1100 nm. This broad range of usable wavelengths has allowed many organisms to thrive in unique environments. Roseiflexus castenholzii is a niche-adapted, filamentous anoxygenic phototroph: FAP) that lacks chlorosomes, the dominant antenna found in all green bacteria. Light-harvesting is realized only in the membrane with BChl a and a variety of carotenoids. Through biochemical and spectroscopic methods, a model for the size and organization of the photosynthetic antenna is presented. Despite the wide distribution of antennas, photochemistry occurs in the reaction center: RC), which can be separated into two groups distinguishable by the identity of the terminal electron acceptor. These are the Fe-S type or type-I and the quinone-type or type -II RCs. All known anoxygenic phototrophs have evolved to utilize only one type of RC. R. castenholzii contains a type-II RC. Through the successful isolation of the RC the kinetics of electron transfer have been investigated by ultrafast pump-probe spectroscopy. Lastly, the energetics of some of the RC cofactors were determined by using redox titrations. The combination of the antenna model and RC kinetics and energetics allows for a nearly complete model of the primary photochemistry in Roseiflexus castenholzii and the expansion of photosynthetic data available among FAPs.


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