Characterization of chasmoendolithic community in Miers Valley, McMurdo Dry Valleys, Antarctica.

The Antarctic Dry Valleys are unable to support higher plant and animal life and so microbial communities dominate biotic ecosystem processes. Soil communities are well characterized, but rocky surfaces have also emerged as a significant microbial habitat. Here, we identify extensive colonization of weathered granite on a landscape scale by chasmoendolithic microbial communities.

Evidence of species recruitment and development of hot desert hypolithic communities.

Hypoliths, photosynthetic microbial assemblages found underneath translucent rocks, are widely distributed within the western region of the Namib Desert and other similar environments. Terminal restriction fragment length polymorphism (T-RFLP) analysis was used to assess the bacterial community structure of hypoliths and surrounding soil (below and adjacent to the hypolithic rock) at a fine scale (10 m radius). Multivariate analysis of T-RFs showed that hypolithic and soil communities were structurally distinct.

Hypolithic microbial communities: between a rock and a hard place.

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.

Stochastic and deterministic processes interact in the assembly of desert microbial communities on a global scale.

Extreme arid regions in the worlds' major deserts are typified by quartz pavement terrain. Cryptic hypolithic communities colonize the ventral surface of quartz rocks and this habitat is characterized by a relative lack of environmental and trophic complexity. Combined with readily identifiable major environmental stressors this provides a tractable model system for determining the relative role of stochastic and deterministic drivers in community assembly.

Ancient origins determine global biogeography of hot and cold desert cyanobacteria.

Factors governing large-scale spatio-temporal distribution of microorganisms remain unresolved, yet are pivotal to understanding ecosystem value and function. Molecular genetic analyses have focused on the influence of niche and neutral processes in determining spatial patterns without considering the temporal scale. Here, we use temporal phylogenetic analysis calibrated using microfossil data for a globally sampled desert cyanobacterium, Chroococcidiopsis, to investigate spatio-temporal patterns in microbial biogeography and evolution.

Cyanobacteria and chloroflexi-dominated hypolithic colonization of quartz at the hyper-arid core of the Atacama Desert, Chile.

Quartz stones are ubiquitous in deserts and are a substrate for hypoliths, microbial colonists of the underside of such stones. These hypoliths thrive where extreme temperature and moisture stress limit the occurrence of higher plant and animal life. Several studies have reported the occurrence of green hypolithic colonization dominated by cyanobacteria.

Hypolithic microbial community of quartz pavement in the high-altitude tundra of central Tibet.

The hypolithic microbial community associated with quartz pavement at a high-altitude tundra location in central Tibet is described. A small-scale ecological survey indicated that 36% of quartz rocks were colonized. Community profiling using terminal restriction fragment length polymorphism revealed no significant difference in community structure among a number of colonized rocks.

Endolithic microbial colonization of limestone in a high-altitude arid environment.

The morphology of endolithic colonization in a limestone escarpment and surrounding rocky debris (termed float) at a high-altitude arid site in central Tibet was documented using scanning electron microscopy. Putative lichenized structures and extensive coccoid bacterial colonization were observed. Absolute and relative abundance of rRNA gene signatures using real-time quantitative polymerase chain reaction and phylogenetic analysis of environmental phylotypes were used to characterize community structure across all domains.

Thermophilic microbial mats in a tropical geothermal location display pronounced seasonal changes but appear resilient to stochastic disturbance.

We demonstrate for the first time a dynamic seasonality within thermophilic mat communities in a tropical geothermal spring. Biomass fluctuated such that it is greatest in the dry season, before falling drastically as the summer rains arrive, and then re-colonization culminates in a new climax in the following dry season. Species richness estimates based upon 16S rRNA gene environmental phylotypes mirrored this pattern, where those unique to the dry season disappear during the wet season only to reappear the following year, and vice versa.

Hypolithic community shifts occur as a result of liquid water availability along environmental gradients in China's hot and cold hyperarid deserts.

Hypolithic cyanobacterial communities occur in hot and cold hyperarid environments but the physical factors determining their diversity are not well understood. Here we report hypolithic diversity and colonization of a common quartz substrate at several hyperarid locations in the ancient deserts of north-western China, that experience varying mean annual temperature, rainfall and concomitant availability of liquid water in soil. Microscopy and enrichment culture resulted only in Chroococcidiopsis morphotypes which were ubiquitous, but community phylogenetic analysis revealed considerable cyanobacterial and heterotrophic bacterial diversity.

Hypolithic cyanobacteria, dry limit of photosynthesis, and microbial ecology in the hyperarid Atacama Desert.

The occurrence of hypolithic cyanobacteria colonizing translucent stones was quantified along the aridity gradient in the Atacama Desert in Chile, from less arid areas to the hyperarid core where photosynthetic life and thus primary production reach their limits. As mean rainfall declines from 21 to View Article and Find Full Text PDF

Community structure of free-floating filamentous cyanobacterial mats from the Wonder Lake geothermal springs in the Philippines.

Cyanobacterial mats were characterized from pools of 45-60 degrees C in near-neutral pH, low-sulphide geothermal springs in the Philippines. Mat structure did not vary with temperature. All mats possessed highly ordered layers of airspaces at both the macroscopic and microscopic level, and these appear to be an adaptation to a free-floating growth habit.

Community phylogenetic diversity of cyanobacterial mats associated with geothermal springs along a tropical intertidal gradient.

The 16S rRNA gene-defined bacterial diversity of tropical intertidal geothermal vents subject to varying degrees of seawater inundation was investigated. Shannon-Weaver diversity estimates of clone library-derived sequences revealed that the hottest pools located above the mean high-water mark that did not experience seawater inundation were most diverse, followed by those that were permanently submerged below the mean low-water mark. Pools located in the intertidal were the least biodiverse, and this is attributed to the fluctuating conditions caused by periodic seawater inundation rather than physicochemical conditions per se.

Community phylogenetic analysis of moderately thermophilic cyanobacterial mats from China, the Philippines and Thailand.

Most community molecular studies of thermophilic cyanobacterial mats to date have focused on Synechococcus occurring at temperatures of approximately 50-65 degrees C. These reveal that molecular diversity exceeds that indicated by morphology, and that phylogeographic lineages exist. The moderately thermophilic and generally filamentous cyanobacterial mat communities occurring at lower temperatures have not previously been investigated at the community molecular level.