Biology of the Chlorophyll D-Containing Cyanobacterium Acaryochloris Marina

Oxygenic phototrophs (cyanobacteria, algae and higher plants) primarily absorb solar energy in the visible spectral (400–700 nm) region by use of various chlorophylls, while anoxygenic phototrophs are bacteria, which can absorb infrared wavelengths (>700–1100 nm) by use of different bacteriochlorophylls (Overmann and Garcia-Pichel, 2004). Each of the groups also has a variety of characteristic antenna pigments and other accessory pigments that can enhance light capture and/or provide protection against excess actinic light and UV-radiation in specific habitats. However, amongst these broadly defined groups there are outlier organisms exhibiting atypical photopigmentation. Amongst the oxygenic phototrophs, the most conspicuous are:

• 1. The endolithic green alga Ostreobium sp. that inhabits coral skeletons and thrives under extreme shade below the coral tissue due to possession of a special Chl a antenna absorbing in the far-red region around 700–730 nm (Halldal, 1968; Fork and Larkum, 1989; Koehne et al., 1999), that is a region of the solar spectrum which is not absorbed by the overlying coral tissue (Magnusson et al., 2007);

• 2. The prochlorophytes present three independent lineages of cyanobacteria, that is the genera Prochlorococcus, Prochlorothrix and Prochloron. Prochlorococcus contains unique divinyl-Chl a and divinyl-Chl b photopigments and only minor amounts of phycobiliprotein (PBP) pigment, while Prochlorothrix and Prochloron are the only prokaryotes containing Chl b (Partensky and Garczarek, 2003).