Fontibacterium commune gen. nov. sp. nov.

Aerobic, chemoorganoheterotrophic, and oligotrophic. Cells are small, curved rods roughly 1 × 0.1 µm. Non-motile. On the basis of phylogenomics and 16S rRNA gene phylogenetics, subclade IIIb/LD12 occurs on a separate branch within the Pelagibacteraceae (SAR11), sister to subclade IIIa containing strains HIMB114 and IMCC9063. Owing to the depth of branching between these clades using concatenated protein-coding genes, and the 92 and 91% 16S rRNA gene sequence identity with HIMB114 and IMCC9063, respectively, we propose LSUCC0530 and subclade IIIb/LD12 as a novel genus in the Pelagibacteraceae.

In addition to the properties given in the genus description, the species is described as follows. Growth occurs at temperatures between 23 °C and 30 °C, but not at 11 °C or below, nor at 35 °C or above. Optimal salinity is 1.45 and below, and growth occurs between 0.36 and 4.68. At optimal temperature and salinity, cells divide at an average rate of 0.52 day^-1. Genome size is 1.16 Mbp, with 1271 predicted genes, and a GC content of 29.02% (calculated). LSUCC0530 had an ANI of 75.3 and 75.9% and an AAI of 58.1 and 59.7% with HIMB114 and IMCC9063, respectively. The genome is available on GenBank under accession number CP024034.