Hypolithic microbial communities: between a rock and a hard place

Abstract

Summary Drylands are the largest terrestrial biome on Earth and a ubiquitous feature is desert pavement terrain, comprising rocks embedded in the mineral soil surface. Quartz and other translucent rocks are common and microbial communities termed hypoliths develop as biofilms on their ventral surfaces. In extreme deserts these represent major concentrations of biomass, and are emerging as key to geobiological processes and soil stabilization. These highly specialized communities are dominated by cyanobacteria that support diverse heterotrophic assemblages. Here we identify global‐scale trends in the ecology of hypoliths that are strongly related to climate, particularly with regard to shifts in cyanobacterial assemblages. A synthesis of available data revealed a linear trend for colonization with regard to climate, and we suggest potential application for hypoliths as ‘biomarkers’ of aridity on a landscape scale. The potential to exploit the soil‐stabilizing properties of hypolithic colonization in environmental engineering on dryland soils is also discussed.

Ecology and biogeochemistry of cyanobacteria in soils, permafrost, aquatic and cryptic polar habitats

“…While these niches may be physically dominated by cyanobacteria, they include a wide range of bacterial and fungal phylotypes. BSCs are found on soil surfaces, while lithic communities depend on the mineral substrate (Vincent 2004; Budel and Colesie Bahl et al (2011, Chan et al (2012), Cowan and Tow (2004), Cowan et al (2011), De La Torre et al (2003, Friedmann et al (1988), Jungblut et al (2005), Khan et al (2011), Pointing et al (2009), Smith et al (2006, Taton et al (2003a, b), Wong et al (2010), and Wood et al (2008a, b) 2014; Makhalanyane et al 2014). BSCs are a dominant feature of many semi-arid and arid environments, and are thought to significantly improve the stability and nutrient status of soils (Belnap and Lange 2002).…”

“…The variability in the environmental factors, together with the less than ideal levels of nutrients required for biological activity, severely restrict microbial communities in polar environments. In the absence of other photoautotrophic clades, it is accepted that cyanobacteria are largely responsible for providing the most important ecosystem services, and that cyanobacterial autotrophy supports substantial and diverse populations of heterotrophic microorganisms (such as Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes) together with smaller numbers of organisms in higher trophic levels (Aislabie et al 2006;Babalola et al 2009;Chan et al 2012;Stomeo et al 2012;Makhalanyane et al 2013a;de los Rios et al 2014;Yung et al 2014).…”

“…Both classical and modern microbiological techniques have highlighted the presence of cyanobacteria in a wide range of terrestrial Arctic and Antarctic niches, including permafrost (Jansson and Tas¸ 2014), ice shelves Bottos et al 2008), rocks (Chan et al 2012;de los Rios et al 2014;Makhalanyane et al 2014), ponds and lakes (Taton et al 2003b;Bonilla et al 2005), glaciers and the resulting meltwater streams (Nadeau and Castenholz 2000;Jungblut et al 2005), and mineral soils (Wood et al 2008b; Lee et al 2012;Makhalanyane et al 2013a). Cyanobacteria are thought to be the primary colonizers in these niches (Vincent 2000), and are known to contribute to structural stability, moisture retention and fertility (Belnap and Gardner 1993).…”

Microbial Diversity in Soil, Sand Dune and Rock Substrates of the Thar Monsoon Desert, India

“…Soil surfaces may support well-defined biological soil crusts dominated by cyanobacteria, fungi, lichens and mosses, and these have been extensively studied [7]. Similarly the cyanobacterial and lichenized lithic microbial communities of desert pavements and exposed rocks have also received significant recent attention [2,5,8]. Relatively less attention has focused on open soils and sand dunes and these have been shown in a few studies to be dominated by a small number of heterotrophic bacterial phyla [9][10][11].…”

“…Desert soil microbiology has been shown to differ fundamentally from that in other biomes [3], and lithic niches also support unique microbial communities [2,4]. Biodiversity of desert microbial communities has been relatively well studied (see for example recent reviews: [2,5,6]. Soil surfaces may support well-defined biological soil crusts dominated by cyanobacteria, fungi, lichens and mosses, and these have been extensively studied [7].…”