Culturable Bacteria in Subglacial Sediments and Ice from Two Southern Hemisphere Glaciers

Abstract

Viable prokaryotes have been detected in basal sediments beneath the few Northern Hemisphere glaciers that have been sampled for microbial communities. However, parallel studies have not previously been conducted in the Southern Hemisphere, and subglacial environments in general are a new and underexplored niche for microbes. Unfrozen subglacial sediments and overlying glacier ice samples collected aseptically from the Fox Glacier and Franz Josef Glacier in the Southern Alps of New Zealand now have been shown to harbor viable microbial populations. Total direct counts of 2-7 x 10(6) cells g(-1) dry weight sediment were observed, whereas culturable aerobic heterotrophs ranged from 6-9 x 10(5) colony-forming units g(-1) dry weight. Viable counts in the glacier ice typically were 3-4 orders of magnitude smaller than in sediment. Nitrate-reducing and ferric iron-reducing bacteria were detected in sediment samples from both glaciers, but were few or below detection limits in the ice samples. Nitrogen-fixing bacteria were detected only in the Fox Glacier sediment. Restriction fragment analysis of 16S rDNA amplified from 37 pure cultures of aerobic heterotrophs capable of growth at 4 degrees C yielded 23 distinct groups, of which 11 were identified as beta-Proteobacteria. 16S rDNA sequences from representatives of these 11 groups were analyzed phylogenetically and shown to cluster with bacteria such as Polaromonas vacuolata and Rhodoferax antarcticus, or with clones obtained from permanently cold environments. Chemical analysis of sediment and ice samples revealed a dilute environment for microbial life. Nevertheless, both the sediment samples and one ice sample demonstrated substantial aerobic mineralization of 14C-acetate at 8 degrees C, indicating that sufficient nutrients and viable psychrotolerant microbes were present to support metabolism. Unfrozen subglacial sediments may represent a significant global reservoir of biological activity with the potential to influence glacier meltwater chemistry.

Comparative analysis of metagenomes from three methanogenic hydrocarbon-degrading enrichment cultures with 41 environmental samples

“…Total DNA from NAPDC used for 16S rRNA gene pyrosequencing was extracted and PCR amplified performed as described by Foght et al (2004) and Tan et al (2013). All 16S rRNA gene pyrotag sequencing reads were generated using the same 'universal' primer set, 926 F and 1392 R, targeting the V6-V8 regions of the 16S rRNA gene of bacteria and archaea .…”

“…Additionally, total DNA was obtained from two oil sands tailings ponds located in Alberta, Canada: MLSB (the same tailings pond used for enrichment of the NAPDC and SCADC cultures), and Tailings Pond 6 (TP6; RamosPadrón et al, 2011). These tailings samples were collected and handled as described by An et al (2013) before total DNA isolation using the beadbeating methods described by Ramos-Padrón et al (2011) for TP6 andFoght et al (2004) for MLSB. DNA was sequenced on a half plate using the GS FLX Titanium Sequencing Kit XLR70 (Roche Diagnostics, Laval, QC, Canada) at McGill University and the Génome Québec Innovation Centre, Montreal, Canada.…”

Subglacial methanogenesis: A potential climatic amplifier?

“…[5] Viable microbes have now been detected in significant concentrations (10 4 -10 7 cells mL À1 ) beneath all types of ice mass, including small valley glaciers [Sharp et al, 1999;Foght et al, 2004], polythermal-based glaciers [Skidmore et al, 2000], ice caps [Gaidos et al, 2004], and the Greenland [Kivimaki, 2004;Christner et al, 2003;Miteva et al, 2004] and Antarctic ice sheets [Mikucki et al, 2004;Christner et al, 2006]. These viable microbes include methanogens, found in basal ice from Greenland (via GISP2 [Tung et al, 2005]) and John Evans Glacier, Canada [Skidmore et al, 2000].…”

“…[3] Subglacial environments are now known to harbor significant numbers of microorganisms (10 6 -10 7 cells mL À1 including methanogens [Sharp et al, 1999;Skidmore et al, 2000;Foght et al, 2004;Price and Sowers, 2004]) and are likely to be anoxic [Wadham et al, 2004;Tranter et al, 2005;Wynn et al, 2006]. There are three important prerequisites for subglacial methane production; that anoxic conditions prevail, that a suitable carbon substrate exists (e.g., overridden soil carbon) and that physical conditions are favorable (e.g., meltwater is present).…”

Microbial nitrogen cycling on the Greenland Ice Sheet

“…Nitrogen fixation can be active in cryoconite (surface sediment) holes on smaller Arctic valley glaciers, suggesting that nitrogen inputs from snowmelt, icemelt and organic remineralization can be insufficient to meet the demands of microbial growth (Telling et al, 2011). Microorganisms capable of nitrogen fixation have also been documented in sediment on a New Zealand glacier (Foght et al, 2004). Mass balance considerations suggest that nitrification may be important in glacial catchments in the Arctic (Hodson et al, 2005;Wynn et al, 2007), the Alps (Tockner et al, 2002), the Rockies (Baron et al, 1995;Campbell et al, 2000), and the maritime Antarctic (Hodson, 2006;).…”