An in silico approach to characterize the resistance against heavy metals and UV-B radiation of poly-extremophilic Nesterenkonia strains

ALVARADO, NN; PALOPOLI, N; ALBARRACÍN V. H.

Corrientes

Congreso; IIX Congreso Argentino de Bioinformática y Biología Computacional; 2022

Asociación Argentina de Bioinformática y Biología Computacional

An in silico approach to characterize the resistance against heavy metals and UV-B radiation ofpoly-extremophilic Nesterenkonia strainsNatalia N. Alvarado (1), Nicolás Palopoli (2), Virginia H. Albarracín (1)1. Centro Integral de Microscopía Electrónica (CIME), CCT-CONICET, UNT, Tucumán, Argentina.2. Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes - CONICET, Bernal,Buenos Aires, Argentina.BACKGROUNDNesterenkonia is a genus of halophilic actinobacteria that thrive in extreme environments such asthe High Altitude Andean Lakes (HAAL) in the South American Central Andes. These microbialcommunities present unique mechanisms to adapt to adverse conditions such as high levels ofultraviolet radiation, hypersalinity, desiccation, high concentration of heavy metals, andtemperature fluctuations. We previously demonstrated that the UV-B and heavy metals resistanceprofiles of Nesterenkonia Act20 (Act20), isolated from HAALS, are superior than those ofNesterenkonia halotolerans YIM70084 (NH), a reference strain from high salinity soils in China.Here we compare computational genome-wide annotations of Act20 and NH, previously obtainedin our group, with other reference organisms to pinpoint candidate genes that could explain theresistance (or lack thereof) to stress in Nesterenkonia. Sequence-based analysis of amino acidresidue conservation provides further details about the best candidate proteins.RESULTSWe found that high UV-B resistance could be related with differences in CPD photolyases, a class oflight-dependent enzymes that repair DNA damage caused by formation of cyclobutane pyrimidinedimers induced by ultraviolet light. We observed that the predicted Act20 CPD photolyase gene is48.88% identical to the well-described CPD photolyase PhrA of Agrobacterium tumefaciens.Moreover, almost all of the amino acid residues that constitute the binding site for 5,10-MTHF asan antenna chromophore, as well as those that bind DNA and FAD, are conserved at the proteinlevel. In contrast, the putative NH CPD photolyase has a lower identity of 22.69% with PhrA, andbarely any conservation of functional residues.CONCLUSIONSAlthough Act20 and NH might be very similar (i.e., their 16 S-rDNA sequences share 97.4%identity), we found significant differences in coding genes that may account for the observed stressresponses. We propose that a CDP photolyase has an essential role for the high UV-B resistance inNesterenkonia Act20 that is absent in NH. Experimental validation will allow us to test thishypothesis. We also observed suggesting differences between Act20 and NH in genes that mediatecopper sequestration, although similar computational analysis are needed to characterize theheavy metal resistance profiles