Extremophile Culture Collection from Andean Lakes: Extreme Pristine Environments that Host a Wide Diversity of Microorganisms with Tolerance to UV Radiation

Abstract

A total of 88 bacterial strains were isolated from six Andean lakes situated at altitudes ranging from 3,400 to 4,600 m above sea level: L. Aparejos (4,200 m), L. Negra (4,400 m), L. Verde (4,460 m), L. Azul (4,400 m), L. Vilama (4,600 m), and Salina Grande (3,400 m). Salinity ranged from 0.4 to 117 ppm. General diversity was determined by denaturing gradient gel electrophoresis (DGGE) analysis. From the excised DGGE bands, 182 bacterial sequences of good quality were obtained. Gammaproteobacteria and Cytophaga/Flavobacterium/Bacteroides (CFB) were the most abundant phylogenetic groups with 42% and 18% of identified bands, respectively. The isolated strains were identified by sequence analysis. Isolated bacteria were subjected to five different UV-B exposure times: 0.5, 3, 6, 12, and 24 h. Afterwards, growth of each isolate was monitored and resistance was classified according to the growth pattern. A wide interspecific variation among the 88 isolates was observed. Medium and highly resistant strains accounted for 43.2% and 28.4% of the isolates, respectively, and only 28.4% was sensitive. Resistance to solar radiation was equally distributed among the isolates from the different lakes regardless of the salinity of the lakes and pigmentation of isolates. Of the highly resistant isolates, 44.5% belonged to gammaproteobacteria, 33.3% to betaproteobacteria, 40% to alphaproteobacteria, 50% to CFB, and among gram-positive organisms, 33.3% were HGC and 44.5% were Firmicutes. Most resistant strains belonged to genera like Exiguobaceterium sp., Acinetobacter sp., Bacillus sp., Micrococcus sp., Pseudomonas sp., Sphyngomonas sp., Staphylococcus sp., and Stenotrophomonas sp. The current study provides further evidence that gammaproteobacteria are the most abundant and the most UV-B-resistant phylogenetic group in Andean lakes and that UV resistance in bacteria isolated from these environments do not depend on pigmentation and tolerance to salinity.

Genome comparison of two Exiguobacterium strains from high altitude andean lakes with different arsenic resistance: identification and 3D modeling of the Acr3 efflux pump

“…The study of HAAL allowed isolation of bacteria resistant to UVR, antibiotic, arsenic and other extreme factors (Fernandez Zenoff et al, 2006;Dib et al, 2008;Flores et al, 2009;Ordoñez et al, 2009). In this place a predominance of Exiguobacterium spp.…”

“…The HAAL ecosystems are systems of shallow lakes formed during the Tertiary geological period (Seufferheld et al, 2008;Farias et al, 2011). These ecosystems are unique not only for their geographical characteristics and broad range of extreme environments but also for their abundant biodiversity (Fernandez Zenoff et al, 2006;Dib et al, 2008;Seufferheld et al, 2008;Flores et al, 2009;Ordoñez et al, 2009;Albarracín et al, 2011;Farias et al, 2013). In these environments high concentrations of arsenic were described in the water due to a natural geochemical phenomenon (Mantelli et al, 2003;Romero et al, 2003;Escudero et al, 2007;Dib et al, 2008Dib et al, , 2009Escalante et al, 2009).…”

“…In these environments high concentrations of arsenic were described in the water due to a natural geochemical phenomenon (Mantelli et al, 2003;Romero et al, 2003;Escudero et al, 2007;Dib et al, 2008Dib et al, , 2009Escalante et al, 2009). The high concentration of arsenic present in HAAL is strongly limiting not only for human life but also for growth of many microorganisms (Valko et al, 2005) and selects development of arsenic tolerant bacteria (Dib et al, 2008;Ordoñez et al, 2009). Different concentrations of arsenic (maximum values) were reported in these environments, 2.3 mg L −1 in Tebenquiche Lake (Farías et al, 2014), 9.1 mg L −1 in Salar de Llamara , 0.8-11.8 mg L −1 in Andean Lakes , 0.9-28 mg L −1 in salt lakes (Lara et al, 2012).…”

Experimental evolution of Bacillus subtilis

“…They have been isolated everywhere from the upper layers of the atmosphere to the depths of ocean trenches, and from almost every conceivable environment in between (Fajardo-Cavazos et al, 2014;Zeigler and Perkins, 2015). Members include not only mesophiles, but acidophiles (Ciuffreda et al, 2015), alikaliphiles (Preiss et al, 2015), halophiles (Hanelt and Muller, 2013), psychrophiles (Larkin and Stokes, 1966), thermophiles (Zeigler, 2014;Hussein et al, 2015) and UV-radiation tolerant organisms (Ordonez et al, 2009). Their physiological capabilities suggest they play a significant role in global carbon, nitrogen and sulphur cycles and in the degradation of plant, fungus and insect biomass (Mandic-Mulec and Prosser, 2011).…”

Towards a Microbial Conservation Perspective in High Mountain Lakes

“…High mountain lakes formed by glaciers erosion are very comparable worldwide ecosystems, and the new lakes that are currently appearing after the glacial retreat in mountain areas offer great opportunities for ecological and limnological studies (Catalan and Rondon 2016). Microbial diversity in high-altitude aquatic ecosystems from highlands such as Tibetan lakes (Zhang et al 2013) and Andean lakes (Ordoñez et al 2009) are not considered here because of the consistent limnological, physicochemical and environmental differences mostly characteristic from the relatively flat terrain of plateau areas.…”