Aerobic Anoxygenic Phototrophic Bacteria

Abstract

SUMMARY The aerobic anoxygenic phototrophic bacteria are a relatively recently discovered bacterial group. Although taxonomically and phylogenetically heterogeneous, these bacteria share the following distinguishing features: the presence of bacteriochlorophyll a incorporated into reaction center and light-harvesting complexes, low levels of the photosynthetic unit in cells, an abundance of carotenoids, a strong inhibition by light of bacteriochlorophyll synthesis, and the inability to grow photosynthetically under anaerobic conditions. Aerobic anoxygenic phototrophic bacteria are classified in two marine (Erythrobacter and Roseobacter) and six freshwater (Acidiphilium, Erythromicrobium, Erythromonas, Porphyrobacter, Roseococcus, and Sandaracinobacter) genera, which phylogenetically belong to the α-1, α-3, and α-4 subclasses of the class Proteobacteria. Despite this phylogenetic information, the evolution and ancestry of their photosynthetic properties are unclear. We discuss several current proposals for the evolutionary origin of aerobic phototrophic bacteria. The closest phylogenetic relatives of aerobic phototrophic bacteria include facultatively anaerobic purple nonsulfur phototrophic bacteria. Since these two bacterial groups share many properties, yet have significant differences, we compare and contrast their physiology, with an emphasis on morphology and photosynthetic and other metabolic processes.

Unexpectedly high bacteriochlorophyll a concentrations in neotropical tank bromeliads

“…3A), providing the conditions necessary for the creation of an anaerobic microcosm (Yavitt, 2010). Therefore, it is conceivable that anaerobic APB, whose BChl a cellular content is up to 50-fold greater than that of aerobic APB (Fleischman and Kramer 1998;Yurkov and Beatty, 1998) form aggregates and are associated with particles producing BChl a once anoxic zones develop.…”

Putative novel photosynthetic reaction centre organizations in marine aerobic anoxygenic photosynthetic bacteria: insights from metagenomics and environmental genomics

“…Indeed, in most species of anaerobic anoxygenic photosynthetic bacteria (AnAnP), the synthesis of photosynthetic apparatus is highly repressed by oxygen and modulated by light intensity (Bowman et al ., 1999). However, since 1979, when the first member of aerobic anoxygenic photosynthetic bacteria (AAnP) has been reported (Shiba et al ., 1979), many AAnP representatives were described from a wide variety of marine, freshwater and terrestrial habitats (Yurkov and Beatty, 1998). These bacteria grow photoheterotrophically, using light as an additional source of energy, and require oxygen for both growth and synthesis of their photosynthetic apparatus.…”

“…These bacteria grow photoheterotrophically, using light as an additional source of energy, and require oxygen for both growth and synthesis of their photosynthetic apparatus. Besides that, AAnPs have some features that distinguish them from the AnAnP group: they contain relatively low amount of photosynthetic units per cell and have high abundance of carotenoid pigments (Yurkov and Beatty, 1998;Rathgeber et al ., 2004).…”

“…Phylogenic relationships based on conserved photosynthetic genes (e.g. pufM ) do not match the 16S-based phylogenies, suggesting that lateral gene transfer may have occurred (Nagashima et al ., 1997;Yurkov and Beatty, 1998). This photosynthesis-related gene clustering offers us the ability to use different genomic approaches, as these approaches are not influenced by the need to grow the AAnP organisms.…”

Aerobic anoxygenic photosynthesis genes and operons in uncultured bacteria in the Delaware River

“…Aerobic anoxygenic photosynthetic (AAP) bacteria appear to be common in oxic aquatic ecosystems (Kolber et al ., 2000;Beja et al ., 2002;Schwalbach and Fuhrman, 2005) and may alter current models of the carbon cycle and other biogeochemical processes (Karl, 2002). Cultured AAP bacteria photosynthesize with the use of bacteriochlorophyll a (bchl a), but do not evolve oxygen (Yurkov and Beatty, 1998). A more thorough understanding of AAP bacteria is needed to elucidate their role in aquatic environments.…”