It undergoes regular seasonal cycles in abundance—in summer reaching ~50% of the cells in the temperate ocean surface waters.

Its discovery was the subject of "Oceans of Microbes", Episode 5 of Intimate Strangers: Unseen Life on Earth by PBS.

They have sensors for nitrogen, phosphate, and iron limitation, and a very unusual requirement for reduced sulfur compounds.

P. communis" can be grown on a defined, artificial medium with additions of reduced sulfur, glycine, pyruvate and vitamins.

P. communis" has the smallest genome (1,308,759 bp) of any free-living organism[6] encoding only 1,354 open reading frames (1,389 genes total).

[14] The only species with smaller genomes are symbionts and parasites, such as Mycoplasma genitalium or Nanoarchaeum equitans[6] 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.

Examples of ncRNA found in these organisms include the SAM-V riboswitch, and other cis-regulatory elements like the rpsB motif.

Subtle differences arise in the expression of its codon sequences when it is subjected to either light or dark treatments.

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 according to rule 12c of the IBCN.

[20] The term "Candidatus" is used for proposed species for which the lack of information[21] prevents it from being a validated species according to the bacteriological code,[22][23] such as deposition in two public cell repositories or lack of FAME analysis,[24][25] whereas "Candidatus Pelagibacter communis" is not in ATCC and DSMZ, nor has analysis of lipids and quinones been conducted.