Variability of the photosynthetic antenna of a Pelodictyon clathratiforme population from a freshwater holomictic pond

Abstract

A population of the green sulfur bacterium Pelodictyon clathratiforme was monitored during the stratification period of Coromina Lake, a freshwater, holomictic pond of the Banyoles lacustrine area (Girona, NE Spain). The chromatographic analysis of this population revealed the presence of a wide variety of both bacteriochlorophyll (BChl) d and BChl c homologues. Isolation of chlorosomes from cultured Pelodictyon cells and their further analysis by steady‐state fluorescence indicated that, although both pigment were present in chlorosomes, only BChl c gave rise to an emission signal, suggesting a fast energy transfer from BChl d to BChl c. Likewise, chlorosomes isolated from natural samples were significantly larger (60–70 nm in width and 115–120 nm in length) than those isolated from cells grown in laboratory under optimal light conditions (48±6.8 nm and 100±15.8 nm in width and length, respectively). The potential role of heterogeneous BChl c‐ and BChl d‐containing chlorosomes and the differences in chlorosome size measured are discussed in terms of the severe light limitation (available light intensity <0.1 μmol photons m−2 s−1 at the bacterial plate) under which the population subsisted during the study period.

Active bacteria and archaea cells fixing bicarbonate in the dark along the water column of a stratified eutrophic lagoon

“…In turn, purple sulfur bacteria were rarely observed on the microscope, agreeing both with the low BChl a concentrations measured (27 μg L −1 , Fig. 1b) and with previous studies (Gich et al , 2001).…”

“…In this regard, the presence of green‐colored three‐dimensional nets composed by cells with ternary fission resembling those of Chlorobium clathratiforme (formerly Pelodictyon clathratiforme ) were easily distinguished on the microscope. This branching species of green sulfur bacteria (GSB) contains bacteriochlorophyll (BChl) c and d (Overmann, 2006) and it has repeatedly been found as the dominant species of GSB in the lagoon (Borrego & Garcia‐Gil, 1994; Gich et al , 2001). In this study, C. clathratiforme constituted a dense population as indicated by the high concentrations of their signature pigments (970 μg L −1 of BChl c + d , Fig.…”

“…and Chlorella sp.) and by anoxygenic phototrophic sulfur bacteria (both purple‐ and green‐colored species) have consistently been reported (Borrego & Garcia‐Gil, 1994; Gich et al , 2001).…”

Green sulphur bacteria as a component of the photosynthetic plankton community in small dimictic humic lakes with an anoxic hypolimnion

“…Chlorobium clathratiforme is known to belong to the green subset of the GSB, and its pigment composition has been reported to be BChl c, d, or both (Gich et al 2001). In Lago di Cadagno, C. clathratiforme covered 95% of the anoxygenic phototrophic community (Habicht et al 2009).…”

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

“…These environments are usually light limited, with typical light intensities ranging from 0.1 to 10 mol of photons m Ϫ2 s Ϫ1 (18,38,39). In nature, browncolored BChl e-containing organisms are frequently found at lower light intensities than those containing BChl c or d (21,25,28,41).…”