This is the network for all anabolic synthesis and it is the subgraph of the pathways for the basic building blocks in the main metabolic chart presented earlier for reductive chemoautotrophs
(Srinivasan and Morowitz, 2009); it is presumably universal for all autotrophs.
This network portrays the canonical chart of autotrophic intermediary metabolism that composes the minimal metabolome of a reductive chemoautotroph. Among the different types of chemical reactions required, a sparse set of simple reactions that dominate and cause chemical transformations stepwise and advance the start compounds through intermediates to the final monomers are represented by arrows that are color-coded (see Supplemental Figure 1, at http://www.biolbull.org/supplemental/).
Our choice of Aquifex is further justified by its placement at the deepest phylogenetic branch point, closest to the last universal common ancestor (Burggraf et al., 1992), and by the fact that it is among the known thermophilic chemoautotrophs whose genomes have been completely sequenced,
At the present time, at least five autotrophic mechanisms have been well established for carbon assimilation (Thauer, 2007; Berg et al., 2007); among these, the reductive TCA cycle (rTCA) is the pathway utilized by many reductive chemoautotrophs (Fuchs, 1989; Nakagawa and Takai, 2008).
Because these two morphotypes were of the same general size and ultrastructure as the two types of symbionts described from other bathymodiolin mussels (Cavanaugh et al., 1987; Fisher et al., 1993; Distel et al., 1995; Fiala-Medioni et al., 2002), we refer to them herein as chemoautotrophic and methanotrophic symbiont morphotypes, or simply as chemoautotrophs and methanotrophs.
azoricus (chemoautotrophs, P = 0.115; methanotrophs, P = 0.383).
heckerae did not differ among the size-classes examined (chemoautotrophs, P = 0.67; methanotrophs, P = 0.342).
The ratio of chemoautotrophs to methanotrophs was also species-specific and independent of size class, with chemoautotrophs much more numerous than methanotrophs (13:1 to 18:1) in B.
The dominance of chemoautotrophs over methanotrophs in B.
There is, however, no positive evidence suggesting that SCB are chemoautotrophs. Bacterial morphology sometimes provides clues to trophic biology (Berkeley, 1979), but the morphology of the SCB from the New Zealand echinoderms was not particularly informative.
None appear to be chemoautotrophs. Molecular techniques will be the best way to investigate the links between host phylogeny and SCB distribution.