Distribution of bacteriochlorophyll homologs in natural populations of brown-colored phototrophic sulfur bacteria

Abstract

The relative content of the four main bacteriochlorophyll (BChl) e homologs of several populations of brown‐colored photosynthetic sulfur bacteria grown in different waterbodies have been measured by high performance liquid chromatography and statistically compared by principal component analysis. All the studied populations possessed representative pigment patterns enriched in highly alkylated bacteriochlorophyll e homologs, with average contents of 0.02±0.01%, 24.92±1.01%, 35.2±0.70%, and 39.9±0.71% for bacteriochlorophyll e1, e2, e3, and e4, respectively. These values clearly differ from those obtained for the same species growing under optimal conditions in laboratory batch cultures (4.99±1.11%, 50.34±1.73%, 28.99±0.63%, and 15.6±1.10% for bacteriochlorophyll e1, e2, e3, and e4, respectively). Multivariate statistical analyses grouped samples into two main clusters, both related to the developmental state of the population. Within these clusters, samples were arranged in several groups according to the physiological pigment response of bacterial populations to light limitation. Although bacteriochlorophyll homolog distribution cannot be considered a real taxonomic character, the data presented demonstrate that it can be useful in field studies since it reflects both the physiological status of the cells and the light regime under which the population has been growing.

Predation impact of ciliated and flagellated protozoa during a summer bloom of brown sulfur bacteria in a meromictic coastal lake

“…The distribution of photosynthetic picoplankton was investigated by means of HPLC separation of photosynthetic pigments followed by photodiode array detection (PDA). The biomass of oxygenic phototrophs was inferred by the concentration of chlorophyll a (Chl a ), while the dynamics of anoxygenic phototrophs were traced by monitoring the variations in the concentration of bacteriochlorophyll e (BChl e ), a well‐known biomarker for brown‐colored species of GSB (Borrego et al , 1997). Variable water volumes ranging from 200 to 700 mL from the sampled depths were prefiltered onto 2 μm Nuclepore ® (Whatman Co.) polycarbonate membranes and then filtered onto GFF glass fiber filters (Millipore Co.).…”

Contribution of deep dark fixation processes to overall CO2 incorporation and large vertical changes of microbial populations in stratified karstic lakes

“…Green Sulfur Bacteria of both green-and brown-colored Chlorobiaceae were identified in all the lakes studied. These bacteria have a great ecological success in the colonization of microenvironments characterized by dim light intensities and high sulfide concentrations (Borrego et al 1997;Marschall et al 2010;Overmann et al 1992).…”

The Role of Carotenoids in the Photoadaptation of the Brown-colored Sulfur Bacterium Chlorobium phaeobacteroides

“…Cb. phaeobacteroides may look brown because of a large amount of aggregated BChl e. Compared with green-colored bacteria, brown-colored bacteria live deeper in the water column where the light is very weak and the spectral range is limited to 400-600 nm (3,4).…”