, 2013 and Chitsaz et al., 2011) it is likely that these taxa also comprise ecologically distinct lineages. Conversely, the recently characterized SAR11 1C, or deep SAR11 clade, maintains high conservation of gene content and gene order when compared
to surface clades (Thrash et al., 2014) indicating that it employs a similar metabolic strategy. The majority of the organic carbon remineralization occurs below the photic zone (del Giorgio and Duarte, 2002) and genes associated with a particle attached lifestyle such as pilus synthesis, protein export, and polysaccharide and antibiotic synthesis genes, appear to be relatively more abundant in deep than surface waters (DeLong et al., 2006). There is also considerable autotrophic carbon assimilation or primary production
in the deep ocean (e.g. Karl et al., 1984, Walsh et al., 2009, Swan et al., 2011 and Anantharaman et al., Selleck BIBW2992 2013). This capacity is apparent selleck screening library in many common and abundant deep sea lineages including the deltaproteobacterial SAR324 clade, and the gammaproteobacterial ARCTIC96BD-19, SUP05, Agg54 and Oceanospirillum clades ( Walsh et al., 2009, Swan et al., 2011 and Anantharaman et al., 2013). These organisms possess genes consistent with the ability to utilize dissimilatory sulfur oxidation for energetic support of autotrophic carbon fixation ( Walsh et al., 2009 and Swan et al., 2011). Mixotrophy and metabolic flexibility appear to be common lifestyle traits
enabling successful habitation of the deep sea. All the above organisms are capable of heterotrophy and, at least for the SAR324, sulfur oxidation and carbon fixation as well as C1 utilization and heterotrophy may all operate in a population simultaneously ADP ribosylation factor ( Sheik et al., 2014). Similarly, the highly abundant heterotrophic Thaumarchaeota also display significant chemoautotrophic metabolism, fuelled by oxidation of ammonia to nitrite ( Berg et al., 2007). Genomic plasticity in the SUP05 clade enables this group to optimize its energy metabolism to suite its local environment. For example, genes involved for H2 and sulfur oxidation are over expressed in hydrothermal plumes, an environment where these electron donors are enriched, while in the background deep-sea a second hydrogenase is more prevalent ( Anantharaman et al., 2013). While many traits have distributions that correlate strictly with the taxonomic structure of the underlying community, such as the variations in photosynthetic capacity described within the picocyanobacteria, other traits, such as nitrogen fixation (e.g. Mahaffey et al., 2005), display a habitat-dependant but taxon-independent distribution. Indeed, several re-analyses of the GOS metagenomics datasets examining different levels of metabolic complexity, including pathways, modules and operons (Gianoulis et al.