Type genome is Fontibacterium meridianamericanum N-IMU-22jan24-050 (GCA_965235635.1), a metagenome-assembled genome (MAG) assembled from 0.5 m depth from Represa de India Muerta, a freshwater reservoir in Uruguay (date: 2024-01-22). N-IMU-22jan24-050 has a genome size of 1.0 Mbp with a genomic GC content of 29.3% and contains 30 tRNAs. The genome is of high quality, consisting of 4 contigs, with a completeness of 95.8%, contamination of 1.2% and strain heterogeneity of 100% as assessed with checkM. The metagenome was assembled with FLYE from combined long-and short-read sequencing (Oxford Nanopore and Illumina NovaSeq). Metagenomic fragment recruitment of >600 samples from five continents indicate that the species is present mainly in subtropical and tropical lakes in South America. The closest cultivated relatives are Fontibacterium commune, syn. ‘Candidatus Fonsibacter ubiquis’ LSUCC0530 (GCF_002688585.1; later reclassified to ‘Ca. Allofontibacter communis’), with an average amino acid identity of 86.94% and average nucleotide identity of 84.39% and another newly proposed species, Fontibacterium abundans MiE-29 (GCA_965235095.1), with an AAI of 90.5% and an ANI of 88.11%. Current GTDB classification (R220): d__Bacteria; p__Pseudomonadota; c__Alphaproteobacteria; o__Pelagibacterales; f__Pelagibacteraceae; g__Fonsibacter; s__