The more distant matches are diverse, and somewhat different for the two subunits. Two sets of putative pyruvate oxidoreductase (Por) genes are found in the BOGUAY genome, one for the homodimeric form (PorABCD, Fig. S6E) related to several

gamma- and betaproteobacterial sequences and another for a possible multisubunit type (PorAB, PorC, PorD, Fig. S7). The PorAB sequence is most closely related to one from Symbiobacterium thermophilum ATCC 14863 (a species also seen in the PorABCD tree), and more distantly to a large group of Bacilli. S. thermophilum is a clostridial strain isolated see more from compost, which grows in apparently obligate association with a Geobacillus strain ( Ohno et al., 2000) from whom it obtains CO2 ( Ueda and Beppu, 2007) and may also have obtained one set of Por genes. The putative PorD and PorC have a somewhat similar set of affiliates, notably including sequences from Thermotogales and diverse Archaea, but appear to be divergent from all of these. The three pathways just considered – the Calvin–Benson–Bassham and

the oxidative and reverse tricarboxylic acid cycles – seem to be encoded by mosaics of vertically and horizontally transmitted genes, with the horizontally transmitted ones often at key branch points. For the CBB, RuBisCO (carrying out the initial carbon fixation step) and one of two possible PPi-dependent 6-phosphofructokinases (proposed to be part of an energy-conserving CBB variant Kleiner et al., 2012) are the only two genes where the BOGUAY inferred Selleck Alpelisib amino acid sequence is not most closely related to that from BgP (where found) or B. alba. In the TCA and rTCA cycles, the carboxylation (rTCA) or decarboxylation (TCA) steps likewise appear Carnitine palmitoyltransferase II to be carried out by enzymes with histories of horizontal transfer (PdhAB, KorAB, AclAB, PorAB, IcdA), with the BOGUAY sequences having few or no close gammaproteobacterial relatives. SdhABC, which can link the (r)TCA cycle to the electron

transport chain in its role as Complex II, appears to have been acquired by the marine Beggiatoaceae (BOGUAY, BgP, BgS) at some point after these diverged from B. alba, or to have been preferentially retained by them. Interestingly, the BOGUAY genome appears to lack the membrane-anchor subunit SdhD, while BgP and B. alba are both annotated as having one (Table S5); if it is actually missing, the connection to electron transport may be as well. Analysis of additional Beggiatoaceae genome sequences should shed light on when and in which species the current patchwork was assembled, and how this process may have been governed by the environmental conditions (oxygen, CO2, and organic carbon availability) encountered by different strains. Identification of a possible sodium:acetate symporter (00830_3288) suggests that the BOGUAY strain may be facultatively heterotrophic.