Diversity of culturable bacteria recovered from Pico Bolívar’s glacial and subglacial environments,at 4950 m,in Venezuelan tropical Andes

Abstract

Even though tropical glaciers are retreating rapidly and many will disappear in the next few years,their microbial diversity remains to be studied in depth. In this paper we report on the biodiversity of the culturable fraction of bacteria colonizing Pico Bolívar’s glacier ice and subglacial meltwaters,at ~4950 m in the Venezuelan Andean Mountains. Microbial cells of diverse morphologies and exhibiting uncompromised membranes were present at densities ranging from 1.5 × 104 to 4.7 × 104 cells/mL in glacier ice and from 4.1 × 105 to 9.6 × 105 cells/mL in subglacial meltwater. Of 89 pure isolates recovered from the samples,the majority were eurypsychrophilic or stenopsychrophilic,according to their temperature range of growth. Following analysis of their 16S rDNA nucleotidic sequence,54 pure isolates were assigned to 23 phylotypes distributed within 4 different phyla or classes: Beta- and Gammaproteobacteria,Actinobacteria,and Bacteroidetes. Actinobacteria dominated the culturable fraction of glacier ice samples,whereas Proteobacteria were dominant in subglacial meltwater samples. Chloramphenicol and ampicillin resistance was exhibited by 73.07% and 65.38%,respectively,of the subglacial isolates,and nearly 35% of them were multiresistant. Considering the fast rate at which tropical glaciers are melting,this study confirms the urgent need to study the microbial communities immured in such environments.