Community Variability of Bacteria in Alpine Snow (Mont Blanc) Containing Saharan Dust Deposition and Their Snow Colonisation Potential

Abstract

Microorganisms uplifted during dust storms survive long-range transport in the atmosphere and could colonize highaltitude snow. Bacterial communities in alpine snow on a Mont Blanc glacier, associated with four depositions of Saharan dust during the period 2006-2009, were studied using 16S rRNA gene sequencing and flow cytometry. Also, sand from the Tunisian Sahara, Saharan dust collected in Grenoble and Mont Blanc snow containing no Saharan dust (one sample of each) were analyzed. The bacterial community composition varied significantly in snow containing four dust depositions over a 3-year period. Out of 61 phylotypes recovered from dusty snow, only three phylotypes were detected in more than one sample. Overall, 15 phylotypes were recognized as potential snow colonizers. For snow samples, these phylotypes belonged to Actinobacteria, Proteobacteria and Cyanobacteria, while for Saharan sand/dust samples they belonged to Actinobacteria, Bacteroidetes, Deinococcus-Thermus and Proteobacteria. Thus, regardless of the time-scale, Saharan dust events can bring different microbiota with no common species set to alpine glaciers. This seems to be defined more by event peculiarities and aeolian transport conditions than by the bacterial load from the original dust source.

Microbial communities and primary succession in high altitude mountain environments

“…An additional important input of microorganisms is from far territories, such as the arid Sahara desert in the case of the European Alps (Kellogg and Griffin 2006). Sandy storms from the Sahara to alpine glaciers carry several types of microbial cells, both in viable and quiescent form (Chuvochina et al 2011(Chuvochina et al , 2012. These cells are physically attached to and protected by microparticles of clay-sized minerals, such as illite and smectite.…”

Potential sources of microbial colonizers in an initial soil ecosystem after retreat of an alpine glacier

“…Mineral debris released after glacier retreat is exposed to continuous atmospheric input (exogenous source) of microbes (Womack et al, 2010) through precipitations (Zhang et al, 2010;Šantl-Temkiv et al, 2012) and dry deposition, such as wind-blown dust and plant debris (Chuvochina et al, 2011;Bowers et al, 2012;DeLeon-Rodriguez et al, 2013). The atmosphere in particular is often wrongly considered sterile because of harsh ultraviolet (UV) radiation and extreme C and nutrient limitations (Womack et al, 2010).…”

Microbial Community Structure of Subalpine Snow in the Sierra Nevada, California

“…While N 2 fixation appears to be a relatively unconserved microbial trait (genus to species level; Martiny et al, 2015), the prevalence of this phylotype and its similarity with A. siamensis suggests that there may be the genetic potential for N 2 fixation in this environment. Previous studies suggested that snow-associated microbial communities are largely derived from eolian movement and deposition of microorganisms (Bowers et al, 2012;Chuvochina et al, 2011b). Windborne dust is one primary vector of such movement, although aerosolized microorganisms do not necessarily require association with dust particles.…”

“…In addition, we recovered four lesser abundant genera (Methylobacterium, Geodermatophilus, Hymenobacter, and Janthinobacterium) that are known to survive in the cryosphere (Chuvochina et al, 2011a;Kim et al, 2012b;Rainey et al, 2005). The first three genera can tolerate high doses of ionizing radiation (Chuvochina et al, 2011b;Rainey et al, 2005), while the fourth is a genus that contains psychrotolerant bacteria (Segawa et al, 2005). Burkholderia, a genus comprised of bacteria found in polar environments and that dominate some subalpine soils (Lipson et al, 2008), was also found in the snowpack, albeit at a low relative abundance (0.15%-0.45% of sequences in upper and lower layers of snow, respectively).…”

“…In addition, montane environments likely receive microbial inputs from different source locations. The few available studies of montane snow-associated microbial communities have revealed microbial densities ranging from 680 to 720,000 cells mL -1 snow (Bauer et al, 2002;Lazzaro et al, 2015;Liu et al, 2009), with a predominance of bacteria in the Proteobacteria and Actinobacteria phyla (Chuvochina et al, 2011b;Liu et al, 2007;Meola et al, 2015). In the Sierra Nevada, California, bacterial abundances were found to range from 9.8 × 10 4 to 5.5 × 10 5 cells mL -1 in white (no algae) and red (algae present) snow areas, respectively (Thomas and Duval, 1995); however, bacterial community composition was not assessed.…”