Bacteria recovered from a high-altitude, tropical glacier in Venezuelan Andes

Abstract

Glacial-ice microorganisms are intensively studied world-wide for a number of reasons, including their psychrophilic lifestyle, their usefulness in biotechnology procedures and their relationship with the search of life outside our planet. However, because of the difficulties for accessing and working at altitudes of >5.000 m above sea level, tropical glaciers have received much less attention than their arctic and antarctic counterparts. In the present work we isolated and characterized a total of forty-five pure isolates originating from direct plating of melted ice collected at the base of a rapidly-retreating, small glacier located at around 4.900 m.a.s.l. in Mount Humboldt (Sierra Nevada National Park, Mérida State, Venezuela). Initial examination of melted ice showed the presence of abundant- (>10⁶ cells ml⁻¹), morphologically diverse- and active bacterial cells, many of which were very small ("dwarf cells"). The majority of the isolates were psychrophilic or psychrotolerant and many produced and excreted cold-active extracellular enzymes (proteases and amylases). The antibiotic tests showed an elevated percentage of isolates resistant to high doses (100 μg/ml) of different antibiotics including ampicillin, penicillin, nalidixic acid, streptomycin, chloramphenicol, kanamycin and tetracycline. Multiresistance was also observed, with 22.22 % of the strains simultaneously resistant up to five of the antibiotics tested. Metal resistance against Ni⁺⁺, Zn⁺⁺ and Cu⁺⁺ was also detected. In accordance with these results, plasmids of low and high molecular weight were detected in 47 % of the isolates. Twenty-two partial 16S rDNA sequences analyzed allowed grouping the isolates within five different phyla/classes: Alpha-, Beta- and Gamma-proteobacteria, Actinobacteria and Flavobacteria. This is the first report concerning South American Andean glacial ice microorganisms.

Clean Low-Biomass Procedures and Their Application to Ancient Ice Core Microorganisms

“…Although microorganisms have been known to be present in glacier ice for nearly a century ( McLean, 1919 ; Darling and Siple, 1941 ), such early findings were largely ignored until microorganisms were investigated in the deep Vostok ice core in the 1980s ( Abyzov et al, 1982 ; Abyzov, 1993 ). This motivated further studies of microorganisms in ice cores collected from polar glaciers, such as the Greenland and Antarctic ice sheets ( Priscu et al, 1998 ; Karl et al, 1999 ; Miteva et al, 2004 ; Tung et al, 2005 ; Knowlton et al, 2013 ), as well as some low-latitude ice caps, such as Guliya, Geladangdong, Zuoqiupu, and Noijinkangsang in China ( Christner et al, 2000 ; Liu et al, 2016 ), Pastoruri in Peru ( Gonzalez-Toril et al, 2015 ), Sajama in Bolivia ( Christner et al, 2000 ), and Mount Humboldt in Venezuela ( Ball et al, 2014 ).…”

The Diversity of Pseudomonas species from the Accumulation Zone of Kanchengayao Glacier, North Sikkim, India

“…The ice core samples from the Accumulation zone of Kanchengayao glacier was aseptically collected in a sterile thermal cryo sampling box. These sterile sampling containers were sealed tightly and were immediately brought to the laboratory [16][17][18][19] . For microbiological analysis, the ice core samples were cut aseptically with a sterilized sawtooth knife and around 5 mm annulus of glacial ice core was discarded 20 .…”

“…After enrichment, bacterial isolation was carried on Pseudomonas isolation agar as mentioned above. Morphologically different colonies were selected and sub-cultured by streak plate method [16][17][18][19] . A total of 22 pure bacterial isolates were isolated from Kanchengayao glacier samples and stored at -80°C in 40% glycerol.…”

“…Similarly, NaCl dependent growth profile was determined by incubating bacterial isolates in LB media containing different concentrations of NaCl (0%, 1% 2%, 4%, 6%, 8% and 10%) at 15°C incubator. For 0% NaCl concentration in LB media following media composition was used (Casein enzymic hydrolysate: 10g/L; Yeast Extract: 5g/L; d.w. 1L) and pH dependent growth profile were also checked at different range pH (4, 6, 8 and 10) at 15°C in an incubator [16][17][18][19] .…”

The end of the eternal snows: Integrative mapping of 100 years of glacier retreat in the Venezuelan Andes

“…Interest in detailed studies of glacier coverage in Venezuela has recently renewed, both because of the imminent disappearance of the last glacier on Humboldt Peak and because of demand from research projects related to ice retreat. For example, in a series of pioneer studies in the tropical Andes, psychrophyllic bacteria were recovered from Humboldt Peak glacier (Ball et al 2014) and Bolívar Peak glacier (Balcazar et al 2015;Rondón et al 2016). Currently, a detailed study of primary succession with a chronosequence approach is underway on Humboldt Peak, of which the work presented here is a key first step (within the framework of the Last Venezuelan Glacier project, funded by the National Geographic Society).…”