In either case, PRCs have two related proteins (L/M; D1/D2; PsaA/PsaB) making up a quasi-symmetrical 5-helical core complex with pockets for pigment binding.

[2] The Type II photosynthetic apparatus in non-oxygenic bacteria consists of light-harvesting protein-pigment complexes LH1 and LH2, which use carotenoid and bacteriochlorophyll as primary donors.

[3] LH1 acts as the energy collection hub, temporarily storing it before its transfer to the photosynthetic reaction centre (RC).

[5][6][7] The core complex is anchored in the cell membrane, consisting of one unit of RC surrounded by LH1; in some species there may be additional subunits.

[2] The D1 (PsbA) and D2 (PsbD) photosystem II (PSII) reaction centre proteins from cyanobacteria, algae and plants only show approximately 15% sequence homology with the L and M subunits, however the conserved amino acids correspond to the binding sites of the photochemically active cofactors.

As a result, the reaction centres (RCs) of purple photosynthetic bacteria and PSII display considerable structural similarity in terms of cofactor organisation.

PSII thus provides a source of electrons that can be used by photosystem I to produce the reducing power (NADPH) required to convert CO2 to glucose.

Transduction is presumed to be common in general, but for any single piece of DNA to be routinely transduced would be highly unexpected.