Abstract
Asinibacterium spp. (Family Chitinophagaceae, Phylum Bacteroidota) are abundant in environments contaminated with heavy metals. We characterized the physiology and genome of two Asinibacterium species to elucidate their ability to survive and grow at ambient conditions in the uranium-contaminated environments. Both strains were able to grow at pH 4.5 or 50 mM nitrate under aerobic conditions and did not grow with alternative electron acceptors under anaerobic conditions. Asinibacterium sp. OR53 grew in medium with uranium concentrations up to 300 µM uranium while Asinibacterium sp. OR43 could not grow at uranium concentrations > 200 µM. Elemental mapping using energy dispersive X-ray spectroscopy indicate that uranium co-localized with phosphorus-containing compounds on the cell surface. Genes potentially encoding resistance mechanisms to a variety of heavy metals were detected in the genomes of both strains. The localization of uranium and missing acidic and alkaline phosphatase genes in the genome suggest that biosorption of uranium to the lipopolysaccharide layer might be the mechanism of uranium resistance. In summary, Asinibacterium spp. OR43 and OR53 are physiologically similar to closely related strains within the Chitinophagaceae family but are uniquely acclimated to the presence of uranium and other heavy metals prevalent in the subsurface at Oak Ridge, Tennessee.
Highlights
IntroductionThe family Chitinophagaceae in the phylum Bacteroidota contains among many other genera, the genera Sediminibacterium, Hydrotalea, and Asinibacterium [1,2,3,4]
OR43 and OR53 are similar to other cultured relatives (Tables S1 and S2) and are resistant to elevated concentrations of heavy metals such as uranium (Figure 3), and cobalt and nickel [21]
OR43 and OR53 to uranium, cobalt, and nickel did not necessarily correspond with heavy metal genes identified in the genome
Summary
The family Chitinophagaceae in the phylum Bacteroidota contains among many other genera, the genera Sediminibacterium, Hydrotalea, and Asinibacterium [1,2,3,4]. Described strains belonging to these genera have been found in freshwater (Sediminibacterium and Hydrotalea), sediments (Sediminibacterium and Hydrotalea), soil (Sediminibacterium), and Donkey milk powder (Asinibacterium) [1,2,3,4,5,6]. Sediminibacterium spp. and Hydrotalea spp. are the closest relatives to Asinibacterium lactis [2]. Sequences closely related to Sediminibacterium spp. were detected in freshwater biofilms, eutrophic lakes, salt water, wastewater, and the gut of beetles and cows [7,8,9,10,11,12,13,14,15].
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