V^V Reduction by <i>Polaromonas</i> spp. in Vanadium Mine Tailings

Vanadium
(V) is an important metal with critical industrial and
medical applications. Elevated V contamination, however, can be a
threat to the environment and human health. Microorganisms can reduce
the more toxic and mobile VV to the less toxic and immobile
VIV, which could be a detoxification and energy metabolism
strategy adopted by V-reducing bacteria (VRB). The limited understanding
of microbial responses to V contamination and the mechanisms for VV reduction, however, hamper our capability to attenuate V
contamination. This study focused on determining the microbial responses
to elevated V concentration and the mechanisms of VV reduction
in V tailings. The bacterial communities were characterized and compared
between the V tailings and the less contaminated adjacent mineral
soils. Further, VV-reducing enrichments indicated that
bacteria associated with Polaromonas, a genus belonging
to the family Burkholderiaceae, were potentially
responsible for VV reduction. Retrieved metagenome-assembled
genomes (MAGs) suggested that the Polaromonas spp.
encoded genes (cymA, omcA, and narG) were responsible for VV reduction. Additionally, Polaromonas spp. was metabolically versatile and could use
both organic and inorganic electron donors. The metabolic versatility
of Polaromonas spp. may be important for its ability
to flourish in the V tailings.