Bacterial community of sediments under the Eastern Boundary Current System shows high microdiversity and a latitudinal spatial pattern.

The sediments under the Oxygen Minimum Zone of the Eastern Boundary Current System (EBCS) along Central-South Peru and North-Central Chile, known as Humboldt Sulfuretum (HS), is an organic-matter-rich benthic habitat, where bacteria process a variety of sulfur compounds under low dissolved-oxygen concentrations, and high sulfide and nitrate levels. This study addressed the structure, diversity and spatial distribution patterns of the HS bacterial community along Northern and South-Central Chile using 16S rRNA gene amplicon sequencing. The results show that during the field study period, the community was dominated by sulfur-associated bacteria. Indeed, the most abundant phylum was , while Sva0081 sedimentary group, of the family (the most abundant family), which includes sulfate-reducer and H scavenger bacteria, was the most abundant genus. Furthermore, a spatial pattern was unveiled along the study area to which the family contributed the most to the spatial variance, which encompasses 42 uncharacterized amplicon sequence variants (ASVs), three assigned to . Electrothrix and two to . Moreover, a very high microdiversity was found, since only 3.7% of the ASVs were shared among localities, reflecting a highly diverse and mature community.