the smallest genome (1,308,759 bp) of any free-living organism encoding only 1,354 open reading frames (1,389 genes total). The only species with smaller genomes are intracellular symbionts and parasites, such as Mycoplasma genitalium or Nanoarchaeum equitans It has the smallest number of open reading frames of any free living organism, and the shortest intergenic spacers, but it still has metabolic pathways for all 20 amino acids and most co-factors. Its genome has been streamlined. This streamlining concept is important because it reduces the amount of energy required for cell replication. "Ca. P. communis" saves energy by using the base pairs A and T (≈70.3% of all base pairs) because they contain less nitrogen, a resource that is hard for organisms to acquire. Non-coding RNAs have been identified in "Ca. P. communis" through a bioinformatics screen of the published genome and metagenomic data. Examples of ncRNA found in these organisms include the SAM-V riboswitch, and other cis-regulatory elements like the rpsB motif. Another example of an important ncRNA in "Ca. P. communis" and other SAR11 clade members is a conserved, glycine-activated riboswitch on malate synthase, putatively leading to "functional auxotrophy" for glycine or glycine precursors in order to achieve optimal growth. It is found to have proteorhodopsin genes, which help power light-mediated proton pumps. Subtle differences arise in the expression of its codon sequences when it is subjected to either light or dark treatments. More genes for oxidative phosphorylation are expressed when it is subjected to darkness. Name The name of the genus (Pelagibacter) stems from the Latin neuter noun (but with masculine ending) pelagus ("sea") combined with the suffix -bacter (rod, bacterium), to mean "bacterium of the sea". The connecting vowel is an "i" and not an "o", as the first term is the Latin "pelagus" and not the Greek original πέλαγος (pelagos) (the word pelagus is a Greek word used in Latin poetry, it is a 2nd declension noun with a Greek-like irregular nominative plural pelagē and not pelagi, the Greek word being a 3rd declension neuter in -ος (pl. -η) unrelated with 2nd declension latin words in -us). The name of the specific epithet (ubique) is a Latin adverb meaning "everywhere"; species with the status Candidatus are not validly published so do not have to be grammatically correct, such as having specific epithets having to be adjectives or nouns in apposition in the nominative case or genitive nouns