Pigment Analysis of “ Candidatus Chlorothrix halophila,” a Green Filamentous Anoxygenic Phototrophic Bacterium

Abstract

The pigment composition of "Candidatus Chlorothrix halophila," a filamentous anoxygenic phototrophic bacterium found in Baja California Sur, Mexico, was determined. Previous work showed that bacteriochlorophyll c (BChl c) was the major pigment in "Ca. Chlorothrix halophila," but it was not clear if this bacterium also contains BChl a (J. A. Klappenbach and B. K. Pierson, Arch. Microbiol. 181:17-25, 2004). Here we show that in addition to BChl c, a small amount of a pigment that is spectrally indistinguishable from BChl a is present in cell extracts of "Ca. Chlorothrix halophila." Nevertheless, the BChl a-like pigment from "Ca. Chlorothrix halophila" has a different molecular weight and a different high-performance liquid chromatography elution time than BChl a from other photosynthetic bacteria. Based on mass spectrometry and other spectroscopic analysis, we determined that the BChl a-like pigment in "Ca. Chlorothrix halophila" contains a tetrahydrogeranylgeraniol tail rather than the phytol tail that is present in BChl a. The carotenoids and major BChl c homologs in "Ca. Chlorothrix halophila" were also identified. BChls c were found to be farnesol esterified and geranylgeraniol esterified.

Initial Characterization of the Photosynthetic Apparatus of “ Candidatus Chlorothrix halophila,” a Filamentous, Anoxygenic Photoautotroph

“…The reason for this difference is not clear, and the difference is not likely to be due to the difference in structure of the BChl a of "Ca. Chlorothrix halophila," as the tail is modified and the head group is not modified (23).…”

“…The nature of the photosynthetic apparatus has remained enigmatic as initial investigations suggested that no BChl a was present in the cells and there was no evidence of a reaction center. Recently, the presence of a BChl a variant has been established (23). In this work we characterized the absorbance and fluorescence emission characteristics of whole cells and isolated chlorosomes of "Ca.…”

A Rapid Method for the Extraction and Analysis of Carotenoids and Other Hydrophobic Substances Suitable for Systems Biology Studies with Photosynthetic Bacteria

“…This extraction procedure yields mainly BChl a as well as small amounts of BPh a and some phospholipids, mainly PG. The concentration of BChl a was determined using the molar extinction coefficient of 6 × 10 4 M −1 ·cm −1 at 772 nm [ 48 ]. For the phospholipid calibration, we utilized the fact that the phospholipid ionization rate does not depend on the fatty acid composition [ 47 ]) as well as the fact that PG, PE and phosphatidylcholine appear as DAG fragments in the mass spectrum.…”

Extraction and quantification of pigments in aerobic anoxygenic phototrophic bacteria

“…Pellets were either extracted with cold 100% acetone, a mixture of acetone/methanol (7:2 v/v), or with 95% cold-buffered methanol (2% ammonium acetate), always at -20°C in the dark. The mixture of acetone/methanol (7:2 v/v) was chosen because it is the most used combination in the extraction of bacterial pigments (e.g., Biebl et al 2005;Glaeser and Klug 2005;Biebl and Wagner-Dobler 2006;Koblížek et al 2006;Olson et al 2007;Boldareva et al 2009). Solvent extracts were filtered through Fluoropore PTFE filter membranes (0.2 μm pore size, Merck) to remove cell debris and immediately injected in the HPLC.…”

“…Methanol and acetone are two of the most suitable and widely used pigment extraction solvents due to their good extraction properties and low toxicity (Wright et al 1997). Generally, BChl a has been identified and quantified with methanol (Koblížek et al 2007;Lami et al 2007), acetone (Le Bris et al 1998), or a mixture of both (Koblížek et al 2006;Olson et al 2007). Duration of the extraction period reported in available literature is also variable, ranging from few minutes (Fujimoto et al 2006;Gerjets et al 2009) to 24 h (Hurley and Watras 1991).…”