Rachael Morgan-Kiss
Assistant Professor of Microbiology
Research Interests:
My main research interests focus on adaptation of microorganisms to their environments, in particular extremophilic photosynthetic lifeforms. In an attempt understand how an organism has adapted to fill its unique niche, my research programme has an overarching goal to pursue questions that involve both natural populations of extremophilic photoautotrophs as well as isolated microbes grown under controlled laboratory conditions. I am pursuing a number of ongoing and new projects that encompass this goal.
One extreme environment which is studied in my laboratory is permanently cold ecosystems. More than 70% of the world exists as cold ecosystems that have stable temperatures below or close to the freezing point of water. Photoautotrophic fixation of carbon dioxide into dissolved carbon drives microbial productivity in most low temperature aquatic ecosystems. Despite their global significance, the psychrophiles, and in particular cold adapted photoautrophs, are poorly understood.
Current and Future Projects
In an effort to understand photosynthetic adaptation to persistently low temperature environments, I work on the physiology and biochemistry of the photosynthetic apparatus of two psychrophillic green algae, Chlamydomonas raudensis, and a newly discovered Chlorella sp. C. raudensis was isolated from a permanently ice-covered aquatic environment in the Dry Valleys of Antarctica, where it is adapted to low temperatures, extreme shade, high salinity and year-round stable environmental conditions. Over a decade of work has made this enigmatic alga one of the most well characterized psychrophillic phototrophs to date. In contrast, the Chlorella sp. resides as part of a microbial mat community in a transient pond located near Bratina Island in McMurdo Sound. The natural environment of the Chlorella sp. is highly divergent from the Dry Valley lake environment of C. raudensis, and is characterized by periods of high light and UV exposure, desiccation events, as well as seasonally variable environmental stress conditions. Currently, I am conducting photophysical and basic physiological studies in these psychrophillic algae to gain understanding about the combinatory effects of low temperature and variable environmental stress on photosynthetic adaptation. Upcoming projects will involve enzymological characterization of the RubisCO holoenzyme and sequencing of the chloroplast genome from both psychrophiles.
Another goal of my research is to characterize the phototrophic community diversity from extreme environments. Currently, I am working on vertical distribution of phototrophs in the four main lakes in McMurdo Long Term Ecological Research (McM-LTER) site. The McM-LTER is one of world-wide LTER locations and represents an 'end member' in the group, being the driest and coldest LTER site in the world. Phototroph biodiversity is assessed using independent analyses such as phylogenetics as well as distribution of FAMES and pigment biomarkers. The results of this study will be ultimately used to verify the validity of a newly acquired method of the McM-LTER to assess phytoplankton biodiversity in situ. This method relies on differences Chlorophyll a fluorescence excitation of spectral algal groups, using the BBE FluoroProbe (BBE Molandecke, Germany).
In a new project, we will be returning to the Dry Valley Lakes in the winter of 2008. This work will be part of a collaborative effort to study the microbial populations during the transition from the Antarctic austral summer to winter. My laboratory will be conducting photosynthetic gene expression studies on the native phytoplankton populations as well as studying the functional and structural changes in the photochemical apparatus in monocultures of C. raudensis, which will be transplanted from the laboratory to its native environment. This project will be the first study the Dry Valley Lake populations during the summer to winter transition as well as attempt to link our understanding of a psychrophillic phototroph under controlled laboratory conditions with its response to its natural environment.
Selected Publications:
- Morgan-Kiss R.M., Priscu JC, Pocock T, Gudnaite-Savich L., Hüner NPA (2006) Adaptation and acclimation of photosynthetic microorganisms to permanently cold environments. Microbiol. Molec. Biol. Rev. 70:222-252.
- Morgan-Kiss R.M., Ivanov A. G., Pocock T., Gudynaite-Savitch L., Hüner N. P. (2005) The Antarctic psychrophile, Chlamydomonas raudensis Ettl (UWO241) (Chlorophyceae, chlorophyta) exhibits a limited capacity to photoacclimate to red light. J Phycol. 41 (4): 791-800.
- Morgan-Kiss R.M., Cronan Jr. JE (2004) The Escherichia coli fadK (ydiD) gene encodes an aerobically-regulated short-chain acyl-CoA synthetase. J. Biol. Chem. 279:37324-37333.
- Morgan-Kiss R.M., Wadler C, Cronan Jr., JE (2002) Long-term and homogeneous regulation of the Escherichia coli araBAD promoter by use of a lactose transporter of relaxed specificity. Proc. Natl. Acad. Sci. USA 99:7373-7377.
- Morgan-Kiss R.M., Ivanov AG, Hüner NPA (2002) The Antarctic psychrophile, Chlamydomonas subcaudata, is deficient in state I-state II transitions. Planta 214:435-445.
Faculty: Morgan-Kiss