Oxygen regulation of development of the photosynthetic membrane system in Chloroflexus aurantiacus

Abstract

Oxygen levels which control induction of the assembly of the pigment-protein photosynthetic polypeptides in dark-grown Chloroflexus aurantiacus were determined. The induction signal by low-oxygen tension is not directly related to the respiratory competence of these photosynthetic cells. Cytochrome c554, the primary electron donor to P865+ of the reaction center, is not present in dark-grown respiratory cells but is induced in parallel with bacteriochlorophylls a and c and at similar oxygen partial pressure. The development of these components of the photosynthetic apparatus and its electron transport chain is completely independent of the presence of any detectable light or bacteriochlorophyll c or a pigments in C. aurantiacus.

Comparison of Chloroflexus aurantiacus strain J-10-fl proteomes of cells grown chemoheterotrophically and photoheterotrophically

“…Only one peptide for protein HemD (Caur_2595) and one peptide for protein BchF (Caur_0415) were observed in the global cell lysate fraction (Supplementary Table 2), and no peptides were observed for proteins HemN (Caur_0209), BchI (Caur_1255), BchK (Caur_0138), BchX (Caur_0417), BchG (Caur_2088), and BciC (Caur_0916). Inhabitation experiment suggested that Bchl a and c synthesis were sensitive to the presence of oxygen, especially Bchl c (Foster et al 1986;Oelze 1992). Hence all proteins (except Caur_0117) involved in the formation of BChl a and BChl c (from ALA to the final products) were either uniquely detected or showed a substantial increase in abundance in cells grown photoheterotrophiclly under anoxic condition in the light agreed with inhabitation experiments.…”

The bchU Gene of Chlorobium tepidum Encodes the C-20 Methyltransferase in Bacteriochlorophyll c Biosynthesis

“…As noted above, although such clustering is not pronounced in the C. tepidum genome, analyses of the chlorophyll biosynthesis genes in the green filamentous bacterium Chloroflexus aurantiacus showed more evidence for clustering (16). In Chloroflexus aurantiacus, BChl biosynthesis and chlorosome production are strongly induced when cells are shifted from oxic to anoxic conditions in light (13,27). Interestingly, genes encoding several chlorosome envelope proteins are clustered together with bchK, the BChl c synthase, and a gene encoding a methyltransferase that had been annotated as crtF (26,45) (Fig.…”

Structure of Chlorosomes from the Green Filamentous Bacterium Chloroflexus aurantiacus

“…In contrast to Chlorobi species, C. aurantiacus is a facultatively aerobic bacterium. The expression of BChl synthesis and photosystem structural genes is suppressed in the presence of oxygen (12,29), and therefore more efficient protection of the existing photosynthetic apparatus against singlet oxygen and radical damage may be needed. The mechanism of this modulation of gene expression is not understood, but it may be similar to that found in purple phototrophic bacteria (17).…”