Calcium and the ecology of photosynthesis in purple sulfur bacteria.

The ecological success of purple sulfur bacteria (PSB) is linked to their ability to collect near-infrared solar energy by membrane-integrated, pigment-protein photocomplexes. These include a Core complex containing both light-harvesting 1 (LH1) and reaction centre (RC) components (called the LH1-RC photocomplex) present in all PSB and a peripheral light-harvesting complex present in most but not all PSB. In research to explain the unusual absorption properties of the thermophilic purple sulfur bacterium Thermochromatium tepidum, Ca was discovered bound to LH1 polypeptides in its LH1-RC; further work showed that calcium controls both the thermostability and unusual spectrum of the Core complex.

Genomic basis for the unique phenotype of the alkaliphilic purple nonsulfur bacterium Rhodobaca bogoriensis.

Although several species of purple sulfur bacteria inhabit soda lakes, Rhodobaca bogoriensis is the first purple nonsulfur bacterium cultured from such highly alkaline environments. Rhodobaca bogoriensis strain LBB1 was isolated from Lake Bogoria, a soda lake in the African Rift Valley. The phenotype of Rhodobaca bogoriensis is unique among purple bacteria; the organism is alkaliphilic but not halophilic, produces carotenoids absent from other purple nonsulfur bacteria, and is unable to grow autotrophically or fix molecular nitrogen.

Genomic Features of the Bundle-Forming Heliobacterium .

Eight species of heliobacteria have had their genomes sequenced. However, only two of these genomes have been analyzed in detail, those from the thermophilic and the alkaliphilic . Here we present analyses of the draft genome sequence of a species of heliobacterium that grows optimally at a moderate temperature and neutral pH.

Allochromatium tepidum, sp. nov., a hot spring species of purple sulfur bacteria.

We describe a new species of purple sulfur bacteria (Chromatiaceae, anoxygenic phototrophic bacteria) isolated from a microbial mat in the sulfidic geothermal outflow of a hot spring in Rotorua, New Zealand. This phototroph, designated as strain NZ, grew optimally near 45 °C but did not show an absorption maximum at 915 nm for the light-harvesting-reaction center core complex (LH1-RC) characteristic of other thermophilic purple sulfur bacteria. Strain NZ had a similar carotenoid composition as Thermochromatium tepidum, but unlike Tch.