A grant has been awarded to Drs. Richard Castenholz (University of Oregon), Timothy McDermott (Montana State University), and Scott Miller, and Frank Rrosenzweig (both of University of Montana) to study the unicellular algae of the order Cyanidiales that thrive in extreme environments in Yellowstone National Park (YNP). The sheer numbers, biomass, and brilliant blue-green color establish these algae as a dominant feature of the microbial communities inhabiting acidic geothermal springs and are especially conspicuous in YNP. There is considerable interest in studying how these simple plant-like microorganisms tolerate the extreme environmental features [high temperature, acidity, heavy metal(loid)s] that define their habitat. These algae contain nearly the smallest numbers of genes of all photosynthetic eukaryotic organisms and are also structurally relatively simple. Current efforts have resulted in major discoveries regarding population diversity and dynamics, generating evidence that strongly suggests that UV radiation is a keystone environmental factor that governs the general health and activity of these algae in these harsh environments. The experiments to be conducted in this study will continue to explore the genetic and physiologic mechanisms and processes of these algae with the goal being to better appreciate how these algae thrive in such extreme environments. Gene expression will be studied in response to UV irradiation in pure cultures and in YNP geothermal springs inhabited by these algae. The study of these algae occupies a key link in the study of the thermophilic microorganisms in Yellowstone, and will align closely with the work of other scientists in YNP to maximize research synergy and discovery. This work should also result in an improved understanding of factors that limit the environmental range of plants in general.
YNP is a World Heritage Convention Site and an UNESCO Biosphere Preserve; however, there is a paucity of information for use in assessing the ecological health of YNP (including any temporal changes due to natural or anthropogenic activity). Work in this study represents a critical resource evaluation tool for YNP managers, who depend almost entirely on academic scientists to document the diversity and richness of species within the park. Furthermore, information generated in this study will be used in YNP's education and outreach efforts to educationally enrich the millions of park visitors who marvel at YNP's geothermal pools and springs, with some of the most obvious and frequently viewed springs being those that are home to extensive Cyanidiales mats. Finally, work to be completed in this study also bears on human resource development. Graduate and undergraduate students will obtain important training, helping them acquire positions that are consistent with their early career goals (private sector, graduate school, academia).
General Background Yellowstone National Park (YNP) is a World Heritage Convention Site and an UNESCO Biosphere Preserve. It is one of the few protected geothermal environments on Earth, containing incredibly diverse geothermal features that are home to large populations of uncharacterized and unknown microorganisms that generate the vibrant colors park visitors observe as they stroll along the boardwalks in YNP. Surprisingly, however, there is little information available for assessing the ecological health of YNP at a time when anthropogenic activity has brought about significant changes throughout the Greater Yellowstone Ecosystem. The research conducted in this study represents a critically important tool for park managers to understand the very YNP resources they are charged with monitoring and managing but that do not have a budget to study. Specifically, the research conducted in this study enables their efforts to define organismal diversity and species richness within the park boundaries, linking the various organisms to habitat type, and to understand the normal ebb and flow of the microbial populations that then are reflected by changes in the colors associated with the various geothermal features. Data and scientific publications generated from this project are also important to YNP's education-outreach (E-O) efforts that impact science education and awareness of literally millions of US and international citizens each year. Intellectual Merit In the very acidic environments such as Norris Geyser Basin, the green color associated with the geothermal features derives from the chlorophyll in the algae that proliferate in these warm and acidic environments. The algae studied in this project are known as Cyanidioscyzon, one of only three eukayotic algae that exist in such harsh environments. Plant scientists study Cyanidioscyzon because structurally and genetically it is essentially a simple plant. As such, it is valuable as a model organism for studying how plants respond to their environment, which in this case is quite harsh. Our prior research efforts documented how these algae exhibit annual die-offs during the summer months; the green color fades and corresponds to about a 100-fold decrease in algae viability. It was important to understand whether this was a naturally occurring phenomenon or if it might be linked to anthropogenic activities (e.g. summer is associated with heaviest tourism activity). Knowing that ultraviolet (UV) and visible (VIS) irradiance levels increase in the summer months (referred to as phototoxicity), we examined how these algae respond to the summertime levels of UV and VIS in contrast to the much lower UV/VIS levels that occur during the winter months. In addition to learning more about the ecology of these algae, this type of work is also relevant to the US bioenergy industry because algae are used for biodiesel production. Consequently, it is important to know how to optimize algal growth and to understand their response(s) to environmental cues. This study concerned algal responses to UV/VIS in nature because it is difficult to mimic summer levels of solar irradiance in the laboratory. UV irradiance was controlled by filters placed over the algal mats in the geothermal feature and algae gene expression was studied using gene microarrays. By studying which specific genes are expressed (or not), we can better understand how the algae are responding to their environment. The microarray experiments revealed significant changes in algal gene expression as a result of exposure to elevated UV and VIS, and that patterns of the algal cell response adjusted across low and high irradiance time periods. Expression of genes involved in cell division and DNA replication were negatively correlated with increasing seasonal VIS, which helps explain why these algae undergo a die-off during this time of year; i.e. functions essential to cell replication are being shut down. UV irradiance positively correlated with expression of genes that code for cell stress responses and UV damage repair. The combined UV and VIS expression analyses also provided evidence of a novel functional role for repetitive DNA elements. Expression of the repetitive DNA elements was repressed by VIS, though UV wavelengths appeared to attenuate this repression. Known to influence gene regulation, the complex VIS/UV regulation of DNA repetitive elements suggests they are important at some level in mediating the algal cell’s reaction to UV and VIS irradiance. Broader Impacts This research project contributed to US human resource development by providing advanced training opportunities for one female PhD graduate student and several female undergraduate research interns. The PIs also participated in E-O work that included instructional-type activities with all age- and education-level groups. Within YNP, this E-O activity included informal boardwalk discussions and lectures with park visitors, as well as the PI providing expert scientific consulting for film companies engaged in producing films about Yellowstone’s extreme life. E-O work also involved formal classroom lectures and laboratory exercises that enhanced local science educational opportunities for elementary, middle school and high school students.
