HALOARCHAEA FROM THE ANDEAN PUNA: BIOLOGICAL ROLE IN THE ENERGY METABOLISM OF ARSENIC

ORDOÑEZ OMAR F.; RASUK MARIA CECILIA; SORIA MARIANA N.; CONTRERAS MANUEL; FARIAS MARIA EUGENIA

MICROBIAL ECOLOGY

SPRINGER

Lugar: Berlin; Año: 2018

0095-3628

Biofilms, microbial mats and microbialites dwell under highle limiting conditions (high salinity, extreme aridity, pH and elevated arsenic concentration) in the Andean Puna. Even so, not only recent pioneering studies have described the microbial diversity of different Altiplano lakes, but also revealed unexpectedly diverse microbial communities. Arsenic metabolism is proposed to be an ancient mechanism in microbial life. In fact, some Bacteria and Archaea are able to exploit arsenic as a bioenergetic substrate in either anaerobic arsenate respiration or chemolithotrophic growth on arsenite. Only six aioAB sequences coding for arsenite oxidase and three arrA sequences coding for arsenate reductase from haloarchaea were previously deposited in the NCBI Database. However, no experimental data on their expression and function has been reported. Recently our working group reported in a High-Altitude Andean Lake (HAAL) in Argentinean Puna a prevalence of haloarchaea in a biofilm. Besides, it had a surprisingly high abundance of genes used for anaerobic arsenate respiration (arr) and arsenite oxidation (aio). Herein, were investigated the presence and expression of both genes involved in obtaining energy from arsenic compounds in the communities harboring microbial mats and microbialites, and isolated strains. Their presence was confirmed in metagenomic DNA from Diamante and Tebenquiche Lakes, and the expression of these genes was confirmed by metatranscriptomic RNA samples. Using selective isolation techniques, eighteen microorganisms belonging to the Halorubrum genera (phylum Euryarchaeota) were isolated. The aioA and arrA genes were detected in most of the isolates and their expression was verified in two selected strains. A positive effect of As[III] and A[V] on cell growth was observed in two isolate (DM2 and TC1). Moreover, DM2 was able to oxidize and reduce As. The confirmation of the oxidation/reduction of arsenic and the transcriptional expression of these genes by RT-PCR in DM2 strongly support that the arsenic could be used in bioenergetics processes, by the microorganisms that inhabit these environments.