Relative transcript abundances for bacteriochlorophyll synthesis genes of six different phototrophs. Mean±s.e.m. are shown here for all bacteriochlorophyll synthesis genes of six different phototrophs, expression levels of which are statistically different (P<0.001) between at least a pair of samples. Syne, Synechococcus sp. strain A and B′ Cab, Candidatus Chloracidobacterium thermophilum; GSB, a Chlorobiales population; Rosei, Roseiflexus sp.; Chlor, Chloroflexus sp.; Anaer, novel Anaerolineae-like Chloroflexi population.