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Photosynth Res (2012) 111:173183 DOI 10.1007/s11120-011-9715-4
REGULAR PAPER
Different phycobilin antenna organisations affect the balance between light use and growth rate in the cyanobacterium Microcystis aeruginosa and in the cryptophyte Cryptomonas ovata
Christfried Kunath Torsten Jakob
Christian Wilhelm
Received: 16 September 2011 / Accepted: 8 December 2011 / Published online: 20 December 2011 Springer Science+Business Media B.V. 2011
Abstract During the recent years, wide varieties of methodologies have been developed up to the level of commercial use to measure photosynthetic electron transport by modulated chlorophyll a-in vivo uorescence. It is now widely accepted that the ratio between electron transport rates and new biomass (PFl/BC) is not xed and
depends on many factors that are also taxonomically variable. In this study, the balance between photon absorption and biomass production has been measured in two phycobilin-containing phototrophs, namely, a cyanobacterium and a cryptophyte, which differ in their antenna organization. It is demonstrated that the different antenna organization exerts inuence on the regulation of the primary photosynthetic reaction and the dissipation of excessively absorbed radiation. Although, growth rates and the quantum efciency of biomass production of both phototrophs were comparable, the ratio PFl/BC was twice as high in the cryptophyte in comparison to the cyanobacterium. It is assumed that this discrepancy is because of differences in the metabolic regulation of cell growth. In the cryptophyte, absorbed photosynthetic energy is used to convert assimilated carbon directly into proteins and lipids, whereas in the cyanobacterium, the photosynthetic energy is preferentially stored as carbohydrates.
Keywords Biomass formation Cyanobacteria
Cryptophytes Electron transport rate NPQ
Introduction
Both cryptophytes and cyanobacteria use phycobiliproteins as major light-harvesting antennae. In contrast to the cyanobacteria where the phycobiliproteins form phycobilisomes as a complex structure outside of the thylakoid membrane (for review, see Bailey and Grossman 2008), the cryptophytes contain the phycobiliproteins inside the thylakoid membrane. A second important difference between both phycobilin and antennae concerns the energy transfer from the antennae to the reaction centers. In cyanobacteria, the phycobilisomes are primarily associated with PSII that is associated with the inner antenna proteins CP43 and CP47 only and lacks the outer antenna system LHCII of higher plants and green algae. In cryptophytes, however, a membrane intrinsic Chla/c-binding protein serves as additional light-harvesting complex that shares some sequence similarities...