Metabolic diversity and co-occurrence of multiple Ferrovum species at an acid mine drainage site

Abstract

Background: Ferrovum spp. are abundant in acid mine drainage sites globally where they play an important role in biogeochemical cycling. All known taxa in this genus are Fe(II) oxidizers. Thus, co-occurring members of the genus could be competitors within the same environment. However, we found multiple, co-occurring Ferrovum spp. in Cabin Branch, an acid mine drainage site in the Daniel Boone National Forest, KY. Results: Here we describe the distribution of Ferrovum spp. within the Cabin Branch communities and metagenome assembled genomes (MAGs) of two new Ferrovum spp. In contrast to previous studies, we recovered multiple 16S rRNA gene sequence variants suggesting the commonly used 97% cutoff may not be appropriate to differentiate Ferrovum spp. We also retrieved two nearly-complete Ferrovum spp. genomes from metagenomic data. The genomes of these taxa differ in several key ways relating to nutrient cycling, motility, and chemotaxis. Conclusions: Previously reported Ferrovum genomes are also diverse with respect to these categories suggesting that the genus Ferrovum contains substantial metabolic diversity. This diversity likely explains how the members of this genus successfully co-occur in Cabin Branch and why Ferrovum spp. are abundant across geochemical gradients.

Metagenome-Assembled Genomes of Novel Taxa from an Acid Mine Drainage Environment

“…1 and 2 ). The Ferrovum MAGs (MAG 23 and MAG24) were described in reference 33 , and MAG 7 is closely related to a previously described genome ( 39 , 40 ).…”

“…pH, Fe(II), and D.O. were measured at the time of sample collection and are reported in reference 33 . Red bars indicate MAGs that encode Cyc2.…”

“… a Taxa in italic text were not analyzed in this work because they were either closely related to cultured taxa (e.g., MAG 7) or presented previously (MAGs 24 and 24 [ 33 ]). b NA, not analyzed.…”

“…Nine are from the gammaproteobacterial order Burkholderiales . Two of these were described previously and were not analyzed here ( 33 ). Three encode genes for N 2 fixation (MAGs 20, 21, and 27), six encode genes for carbon fixation, (MAGs 20 to 22, 25, 26, and 28), seven encode genes for Fe(II) oxidation (MAGs 20 to 22 and 25 to 28), and three encode genes for partial sulfate reduction (MAGs 22, 25, and 26).…”

“…Even in well-studied AMD groups such as the Gammaproteobacteria , multiple closely related taxa may occur in AMD sites but may play different roles from their close relatives. For example, multiple Ferrovum taxa differ in their ability to fix nitrogen ( 30 – 33 ). This intragenus metabolic diversity complicates our ability to understand biogeochemical cycling in AMD environments.…”