The cyanobacterial genome core and the origin of photosynthesis

Abstract

Comparative analysis of 15 complete cyanobacterial genome sequences, including ''near minimal'' genomes of five strains of Prochlorococcus spp., revealed 1,054 protein families [core cyanobacterial clusters of orthologous groups of proteins (core CyOGs)] encoded in at least 14 of them. The majority of the core CyOGs are involved in central cellular functions that are shared with other bacteria; 50 core CyOGs are specific for cyanobacteria, whereas 84 are exclusively shared by cyanobacteria and plants and͞or other plastid-carrying eukaryotes, such as diatoms or apicomplexans. The latter group includes 35 families of uncharacterized proteins, which could also be involved in photosynthesis. Only a few components of cyanobacterial photosynthetic machinery are represented in the genomes of the anoxygenic phototrophic bacteria Chlorobium tepidum, Rhodopseudomonas palustris, Chloroflexus aurantiacus, or Heliobacillus mobilis. These observations, coupled with recent geological data on the properties of the ancient phototrophs, suggest that photosynthesis originated in the cyanobacterial lineage under the selective pressures of UV light and depletion of electron donors. We propose that the first phototrophs were anaerobic ancestors of cyanobacteria (''procyanobacteria'') that conducted anoxygenic photosynthesis using a photosystem I-like reaction center, somewhat similar to the heterocysts of modern filamentous cyanobacteria. From procyanobacteria, photosynthesis spread to other phyla by way of lateral gene transfer.cyanobacteria ͉ protein families ͉ lateral gene transfer

Constraining the timing of the Great Oxidation Event within the Rubisco phylogenetic tree

“…However, lines of evidence from extant organismal physiology and Precambrian geochemical indicators corroborate the possibility that some rise in oxygen or other oxidized chemical species preceded the emergence of Form I Rubisco enzymes within cyanobacterial clades. Previous phylogenetic analyses indicate that anoxygenic photosynthetic lineages are more deeply rooted than oxygenic cyanobacterial lineages (Mulkidjanian et al., 2006; Xiong, 2007) and that cyanobacteria represent an evolutionary intermediate between anaerobic and obligate aerobic organisms (Harel, Karkar, Cheng, Falkowski, & Bhattacharya, 2015). Co‐evolution at organismal (i.e., the emergence or development of localized CO 2 or O 2 control volumes within cells) and protein (i.e., direct accumulation of mutations in sequences representing oxygen‐sensitive regions of proteins) levels may have been tightly coupled just prior to the GOE due to oxygen stresses and diminishing CO 2 availability in the near‐surface environment (Knoll, 2006; Tomitani et al., 2006).…”

Genome-wide comparison of cyanobacterial transposable elements, potential genetic diversity indicators

“…A systematical IS element collection and IS family based classification system have been established by some professional databases, such as IS Finder (Siguier et al, 2006) and GenBank. Cyanobacteria, considered as the ancestor of photosynthetic organisms on the earth, consist of large groups of organisms from unicellular to filamentous forms (Mulkidjanian et al, 2006). However, less is known about the transposable elements in cyanobacteria.…”

Anoxygenic photosynthesis modulated Proterozoic oxygen and sustained Earth's middle age

“…In oxygenic cyanobacteria, photosystem I (PSI) strips electrons from chlorophyll to generate energy and reductants (ATP and NADPH), while a second photosystem (PSII), assisted by a Mn-based catalytic complex, replenishes the electron pool by oxidizing H 2 O to O 2 (21). In contrast, green and purple sulfur bacteria (anoxygenic photoautotrophs) commonly use sulfide to drive primary production with PSI-and PSII-like machinery, respectively (22,23). In this case, the production of oxidized sulfur compounds (S 0 or SO 4 ), rather than O 2 , balances the formation of OM.…”