Photochemical changes during rehydration of an intertidal cyanobacterial mat exposed to variations in salinity and light intensity.

This study focuses on a cf. dominated mat community from the intertidal zone of the Laguna Ojo de Liebre, Baja California Sur. In this environment, the mat is desiccated for several days between spring tides.

Phototrophic Co-cultures From Extreme Environments: Community Structure and Potential Value for Fundamental and Applied Research.

Cyanobacteria are found in most illuminated environments and are key players in global carbon and nitrogen cycling. Although significant efforts have been made to advance our understanding of this important phylum, still little is known about how members of the cyanobacteria affect and respond to changes in complex biological systems. This lack of knowledge is in part due to our dependence on pure cultures when determining the metabolism and function of a microorganism.

Phototrophic microbes form endolithic biofilms in ikaite tufa columns (SW Greenland).

Marine tufa-columns, formed by the hydrated carbonate mineral ikaite, present a unique alkaline microbial habitat only found in Ikka Fjord (SW-Greenland). The outermost parts of the ikaite columns exhibit a multitude of physico-chemical gradients, and the porous ikaite is colonized by endolithic phototrophic biofilms serving as a substrate for grazing epifauna, where scraping by sea urchins affects overall column-topography. We present a detailed study of the optical microenvironment, spatial organization, and photosynthetic activity of endolithic phototrophs within the porous ikaite crystal matrix.

Portrait of a Geothermal Spring, Hunter's Hot Springs, Oregon.

Although alkaline Hunter's Hot Springs in southeastern Oregon has been studied extensively for over 40 years, most of these studies and the subsequent publications were before the advent of molecular methods. However, there are many field observations and laboratory experiments that reveal the major aspects of the phototrophic species composition within various physical and chemical gradients of these springs. Relatively constant temperature boundaries demark the upper boundary of the unicellular cyanobacterium, Synechococcus at 73-74 °C (the world-wide upper limit for photosynthesis), and 68-70 °C the upper limit for Chloroflexus.

In situ gene expression profiling of the thermoacidophilic alga Cyanidioschyzon in relation to visible and ultraviolet irradiance.

Ultraviolet and high-intensity visible radiation generate reactive intermediates that damage phototrophic microorganisms. In Yellowstone National Park, the thermoacidophilic alga Cyanidioschyzon exhibits an annual seasonal biomass fluctuation referred to as 'mat decline', where algal viability decreases as ultraviolet and visible irradiances increase during summer. We examined the role irradiance might play in mat decline using irradiance filters that uncouple ultraviolet and visible effects along with custom microarrays to study gene expression in situ.