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Chlorobaculum tepidum regulates chlorosome structure and function in response to temperature and electron donor availability

“…BChl c molecules exist as a set of homologs which differ in the number and identity of alkyl groups on positions 8 and 12 of the chlorin ring (Nozawa et al 1991) that can be resolved by HPLC (Persson et al 2000). Despite being considered low-light specialists (Overmann and Garcia-Pichel 2006), C. tepidum and other green phototrophic bacteria can acclimate to changes in growth light intensity by altering the distribution of BChl c homologs (Bobe et al 1990;Borrego and Garcia-Gil 1994;Borrego et al 1999). More recently, Bryant and coworkers reported that strains carrying mutations in the C. tepidum bchQ and bchR genes, which encode Bacteriochlorophyllide c C-8 2 and C-12 1 methyltransferases, display decreased specific BChl c content, altered Q y absorption maxima, and grew less rapidly at low-light intensities than the wild type.…”

Characterization of Three Homologs of the Large Subunit of the Magnesium Chelatase from Chlorobaculum tepidum and Interaction with the Magnesium Protoporphyrin IX Methyltransferase

“…tepidum produces three types of Chls/Bcls: bacteriochlorophyll c, bacteriochlorophyll a, and Chl a. Bacteriochlorophyll c, the most abundant (B)Chl, is the primary pigment of the chlorosome, a light-harvesting antenna structure, whereas bacteriochlorophyll a and Chl a are the pigments involved in the primary electron transfer reactions in the photosynthetic reaction center complexes (3,6,7). Bacteriochlorophyll c is characterized by a C-3 1 hydroxyl group and the absence of the methoxycarbonyl of ring E. Both characteristics lead to selfassembling properties of bacteriochlorophyll c that extend the absorption properties of the supramolecular complex to longer wavelengths (8,9).…”

Chlorobaculum tepidum Modulates Amino Acid Composition in Response to Energy Availability, as Revealed by a Systematic Exploration of the Energy Landscape of Phototrophic Sulfur Oxidation

“…Bradford and BCA protein assays are simple, rapid, and inexpensive yet exhibit protein-to-protein variability, measure protein indirectly relative to a chosen protein standard, and are subject to interference from a range of compounds, including photosynthetic pigments (26). As C. tepidum pigment content changes in response to the electron donor (12), light intensity (27,28), and culture duration, we used cultures grown across the energy landscape to examine this interference by using AAA as the "gold standard" for protein quantitation (46). This work established that BCA-EX measurements provided good overall accuracy in predicting C. tepidum protein without correction.…”

“…However, excluding individual amino acids from the ϳP avg calculation did not eliminate the re- lationship between ϳP avg and light flux (see Table S4 in the supplemental material), consistent with a globally coordinated alteration of biomass composition. As C. tepidum is known to increase its BChl c content and chlorosome volume fraction in response to decreased light flux (27,28), we considered the possibility that the observed bias in amino acid composition at low light levels could be the result of increased abundance of chlorosome-associated proteins. The BChl c-to-protein ratio increased with decreasing light for sulfideand S 0 -grown cultures, as expected (see Fig.…”

“…However, differences between the amino acid compositions of biomass and protein standards and interference from a range of compounds (26), including photosynthetic pigments, mean that colorimetric protein assays often do not reflect the absolute protein concentration. While pigment extraction prior to protein measurement is common (12,18,25), the effects of extraction and of varying pigment content, induced by changes in light level (27,28) and electron donor (12), have not been investigated systematically.…”