Genome-centric metagenomic insights into the role of Chloroflexi in anammox, activated sludge and methanogenic reactors

BOVIO WINKLER, P.; GUERRERO, L.D.; ERIJMAN, L.; OYARZUA, P.; SUÁREZ-OJEDA, M.E.; CABEZAS, A.; ETCHEBEHERE, C.

BMC MICROBIOLOGY

BIOMED CENTRAL LTD

Lugar: Londres; Año: 2023

1471-2180

The phylum Chloroflexi is highly abundant in diverse wastewater treatment bioreactors. It has been suggested that they play relevant roles in these ecosystems, particularly in degrading carbon compounds and on structuring flocs or granules. Nevertheless, their function is not yet well understood as most species are not present in axenic cultures. Here we used a metagenomic approach to investigate Chloroflexi diversity and their metabolic potential in three completely different bioreactors: a methanogenic full-scale reactor, a full-scale activated sludge reactor and a lab scale anammox reactor. Differential coverage binning approach was used to assemble the genomes of 17 new Chloroflexi species, two of which are proposed as new Candidatus genus. In addition, we recovered the first representative genome belonging to the genus ‘Ca. Villigracilis’. Even though samples analyzed were collected from completely different bioreactors, the assembled genomes share several metabolic features: anaerobic metabolism, fermentative pathways and several genes coding for hydrolytic enzymes. Interestingly, genome analysis from the anammox reactor indicated a putative role of Chloroflexi in nitrogen conversion. Genes related to adhesiveness and exopolysaccharides production were also detected. Complementing sequencing analysis, filamentous morphology was detected by Fluorescent in situ hybridization. Our results suggest that Chloroflexi participate in organic matter degradation, nitrogen removal and biofilm aggregation, playing different roles depending on the environmental conditions