Quantification of viable endospores from a Greenland ice core

Abstract

Endospores (i.e., bacterial spores) embedded in polar ices present an opportunity to investigate the most durable form of life in an ideal medium for maintaining long-term viability. However, little is known about the endospore distribution and viability in polar ices. We have determined germinable endospore concentrations of bacterial spores capable of germination in a Greenland ice core (GISP2 94 m, ID# G2-271) using two complementary endospore viability assays (EVA), recently developed in our laboratory. These assays are based on bulk spectroscopic analysis (i.e., spectroEVA), and direct microscopic enumeration (i.e., microEVA) of ice core concentrates. Both assays detect dipicolinic acid (DPA) release during l-alanine induced germination via terbium ion (Tb3+)-DPA luminescence. Using spectroEVA, the germinable and total bacterial spore concentrations were found to be 295+/-19 spores mL(-1) and 369+/-36 spores mL(-1), respectively, (i.e., 80% of the endospores were capable of germination). Using microEVA, the germinating endospore concentration was found to be 27+/-2 spores mL(-1). The total cell concentration, as determined by DAPI stain fluorescence microscopy, was 7.0 x 10(3)+/-6.7 x 10(2) cells mL(-1). Culturing attempts yielded 2 CFU mL(-1) (4 degrees C). We conclude that endospores capable of germination in the GISP2 ice cores are readily determined using novel endospore viability assays.

Legal immigrants: invasion of alien microbial communities during winter occurring desert dust storms

“…Similarly, viable Bacillus species originating from Chinese deserts were shown to be distributed via the atmosphere to long distance habitats in Japan [32, 33]. The ability to form spores provides resistance to extreme environments [34] and indicates that these genera have a high probability of surviving years of enclosure in the snowpack [35], while for the survival in the troposphere pigmentation seems to be an important factor [4, 8]. Regarding the latter case, the pigmented Deinococcus-Thermus and Gemmatimonadetes were recently considered as bio-indicators for Saharan dust events [8] which is supported by our observations (Additional file 1: Table S4).…”

Recovery of metallo-tolerant and antibiotic resistant psychrophilic bacteria from Siachen glacier, Pakistan

“…These findings strongly support our study as most of the Gram positive bacteria in our study were psychrotrophic and spore formers. Spore formation might help overcome the stress conditions to low temperature, desiccation and damage of bacteria by UV [50–51]. The possible mechanism of survival in Gram negative bacteria could be associated with upregulation of desaturase genes and increase of membrane lipids like Poly-unsaturated fatty acids (PUFAs) in association with decrease in temperature [52, 53].…”

Abundance, viability and diversity of the indigenous microbial populations at different depths of the NEEM Greenland ice core

“…Fungi and algae were also cultivated from these ice cores (Catranis & Starmer 1991;Christner et al 2000;Starmer et al 2005). Over 10% of viable bacterial spores were enumerated in GISP2 ice (Yung et al 2007). Systematic studies of 3043-m-deep silty GISP2 ice detected an abundant and diverse microbial population and recovered isolates including ultrasmall and novel microorganisms (Sheridan et al 2003;Miteva et al 2004;Miteva & Brenchley 2005;LovelandCurtze et al 2008LovelandCurtze et al , 2010.…”