@article {4998, title = {Antarctic lake viromes reveal potential virus associated influences on nutrient cycling in ice-covered lakes}, journal = {Frontiers in Microbiology}, volume = {15}, year = {2024}, month = {09/2024}, abstract = {

The McMurdo Dry Valleys (MDVs) of Antarctica are a mosaic of extreme habitats which are dominated by microbial life. The MDVs include glacial melt holes, streams, lakes, and soils, which are interconnected through the transfer of energy and flux of inorganic and organic material via wind and hydrology. For the first time, we provide new data on the viral community structure and function in the MDVs through metagenomics of the planktonic and benthic mat communities of Lakes Bonney and Fryxell. Viral taxonomic diversity was compared across lakes and ecological function was investigated by characterizing auxiliary metabolic genes (AMGs) and predicting viral hosts. Our data suggest that viral communities differed between the lakes and among sites: these differences were connected to microbial host communities. AMGs were associated with the potential augmentation of multiple biogeochemical processes in host, most notably with phosphorus acquisition, organic nitrogen acquisition, sulfur oxidation, and photosynthesis. Viral genome abundances containing AMGs differed between the lakes and microbial mats, indicating site specialization. Using procrustes analysis, we also identified significant coupling between viral and bacterial communities (p = 0.001). Finally, host predictions indicate viral host preference among the assembled viromes. Collectively, our data show that: (i) viruses are uniquely distributed through the McMurdo Dry Valley lakes, (ii) their AMGs can contribute to overcoming host nutrient limitation and, (iii) viral and bacterial MDV communities are tightly coupled.

}, keywords = {LTER-MCM, Antarctica, bacteria, limnology, metagenomics, virus}, doi = {10.3389/fmicb.2024.1422941}, url = {https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1422941/full}, author = {Robinson, David M. and Rachael M. Morgan-Kiss and Wang, Zhong and Cristina D. Takacs-Vesbach} } @article {4767, title = {An Antarctic alga that can survive the extreme cold}, journal = {Frontiers for Young Minds}, volume = {10}, year = {2022}, month = {05/2022}, pages = {740838}, abstract = {

Microscopic algae are tougher than you might think. Some can even survive the extreme cold. In this article, we describe one of the coolest algae of all, the Antarctic green alga called Chlamydomonas sp. UWO241. This one-celled super-organism lives deep in the frigid waters of a remote and permanently ice-covered lake in Antarctica. How does this little alga thrive in such a barren and unwelcoming place? Well, dive into this article to learn how studying the genome of UWO241 is helping scientists better understand this amazingly hardy alga.

}, keywords = {LTER-MCM}, doi = {10.3389/frym.2022.740838}, url = {https://kids.frontiersin.org/articles/10.3389/frym.2022.740838}, author = {Smith, David R. and Leung, Arthur and Zhang, Xi and Cvetkovska, Marina and Rachael M. Morgan-Kiss and H{\"u}ner, Norman P. A.} } @article {4814, title = {Antarctic lake phytoplankton and bacteria from near-surface waters exhibit high sensitivity to climate-driven disturbance}, journal = {Environmental Microbiology}, year = {2022}, month = {07/2022}, abstract = {

The McMurdo Dry Valleys (MDVs), Antarctica, represent a cold, desert ecosystem poised on the threshold of melting and freezing water. The MDVs have experienced dramatic signs of climatic change, most notably a warm austral summer in 2001\–2002 that caused widespread flooding, partial ice cover loss and lake level rise. To understand the impact of these climatic disturbances on lake microbial communities, we simulated lake level rise and ice-cover loss by transplanting dialysis-bagged communities from selected depths to other locations in the water column or to an open water perimeter moat. Bacteria and eukaryote communities residing in the surface waters (5 m) exhibited shifts in community composition when exposed to either disturbance, while microbial communities from below the surface were largely unaffected by the transplant. We also observed an accumulation of labile dissolved organic carbon in the transplanted surface communities. In addition, there were taxa-specific sensitivities: cryptophytes and Actinobacteria were highly sensitive particularly to the moat transplant, while chlorophytes and several bacterial taxa increased in relative abundance or were unaffected. Our results reveal that future climate-driven disturbances will likely undermine the stability and productivity of MDV lake phytoplankton and bacterial communities in the surface waters of this extreme environment.

}, keywords = {LTER-MCM}, doi = {10.1111/1462-2920.16113}, url = {https://onlinelibrary.wiley.com/doi/10.1111/1462-2920.16113}, author = {Sherwell, Shasten S. and Kalra, Isha and Li, Wei and Diane M. McKnight and John C. Priscu and Rachael M. Morgan-Kiss} } @article {4936, title = {Antibiotic resistance genes and taxa analysis from mat and planktonic microbiomes of Antarctic perennial ice-covered Lake Fryxell and Lake Bonney}, journal = {Antarctic Science}, volume = {34}, year = {2022}, month = {12/2022}, pages = {408 - 422}, abstract = {

The perennial ice-covered lakes of the Antarctic McMurdo Dry Valleys harbour oligotrophic microbial communities that are separated geographically from other aquatic systems. Their microbiomes include planktonic microbes as well as lift-off mat communities that emerge from the ice. We used the ShortBRED protein family profiler to quantify the antibiotic resistance genes (ARGs) from metagenomes of lift-off mats emerging from ice and from filtered water samples of Lake Fryxell and Lake Bonney. The overall proportion of ARG hits was similar to that found in temperate-zone rural ponds with moderate human inputs. Specific ARGs showed distinct distributions for the two lakes and for mat vs planktonic sources. Metagenomic taxa distributions showed that mat phototrophs consisted mainly of cyanobacteria or Betaproteobacteria, whereas the water column phototrophs were mainly protists. An enrichment culture of the Betaproteobacterium Rhodoferax antarcticus from a Lake Fryxell mat sample showed an unusual mat-forming phenotype not previously reported for this species. Its genome showed no ARGs associated with Betaproteobacteria but had ARGs consistent with a minor Pseudomonas component. The Antarctic lake mats and water showed specific ARGs distinctive to the mat and water sources, but overall ARG levels were similar to those of temperate water bodies with moderate human inputs.

}, keywords = {LTER-MCM, microbial mat, Rhodoferax, Taylor Valley}, issn = {0954-1020}, doi = {10.1017/S0954102022000360}, url = {https://www.cambridge.org/core/product/identifier/S0954102022000360/type/journal_article}, author = {Tallada, Sheetal and Hall, Grant and Barich, Daniel and Rachael M. Morgan-Kiss and Slonczewski, Joan L.} } @article {4154, title = {The Antarctic psychrophiles Chlamydomonas spp. UWO241 and ICE-MDV exhibit differential restructuring of photosystem I in response to iron}, journal = {Photosynthesis Research}, volume = {9}, year = {2019}, month = {02/2019}, abstract = {

Chlamydomonas sp. UWO241 is a psychrophilic alga isolated from the deep photic zone of a perennially ice-covered Antarctic lake (east lobe Lake Bonney, ELB). Past studies have shown that C. sp. UWO241 exhibits constitutive downregulation of photosystem I (PSI) and high rates of PSI-associated cyclic electron flow (CEF). Iron levels in ELB are in the nanomolar range leading us to hypothesize that the unusual PSI phenotype of C. sp. UWO241 could be a response to chronic Fe-deficiency. We studied the impact of Fe availability in C. sp. UWO241, a mesophile, C. reinhardtii SAG11-32c, as well as a psychrophile isolated from the shallow photic zone of ELB, Chlamydomonas sp. ICE-MDV. Under Fe-deficiency, PsaA abundance and levels of photooxidizable P700 (ΔA820/A820) were reduced in both psychrophiles relative to the mesophile. Upon increasing Fe, C. sp. ICE-MDV and C. reinhardtii exhibited restoration of PSI function, while C. sp. UWO241 exhibited only moderate changes in PSI activity and lacked almost all LHCI proteins. Relative to Fe-excess conditions (200 μM Fe2+), C. sp. UWO241 grown in 18 μM Fe2+ exhibited downregulation of light harvesting and photosystem core proteins, as well as upregulation of a bestrophin-like anion channel protein and two CEF-associated proteins (NdsS, PGL1). Key enzymes of starch synthesis and shikimate biosynthesis were also upregulated. We conclude that in response to variable Fe availability, the psychrophile C. sp. UWO241 exhibits physiological plasticity which includes restructuring of the photo-chemical apparatus, increased PSI-associated CEF, and shifts in downstream carbon metabolism toward storage carbon and secondary stress metabolites.

}, keywords = {LTER-MCM, Antarctica, Cyclic electron flow, Iron, Photosystem I, Psychrophile}, issn = {0166-8595}, doi = {10.1007/s11120-019-00621-0}, url = {https://link.springer.com/article/10.1007/s11120-019-00621-0}, author = {Cook, Greg and Teufel, Amber and Kalra, Isha and Li, Wei and Wang, Xin and John C. Priscu and Rachael M. Morgan-Kiss} } @mastersthesis {4166, title = {Antarctic Chlamydomonas strains C. sp. UWO241 and ICE-MDV exhibit differential restructuring of the photosynthetic apparatus in response to iron}, volume = {M.S.}, year = {2018}, month = {2018}, school = {Miami University}, type = {masters}, address = {Oxford, OH}, abstract = {

As an integral cofactor for many redox-associated processes, iron (Fe) homeostasis is crucial in order to produce sufficient energy for the organism. Fe limitation, or excess, can cause major alterations in the function and structure of the photosynthetic apparatus. Photosynthetic psychrophiles grown under permanent low temperatures exhibit novel adaptations in their photosynthetic apparatus to deal with this permanent stress. The ice-covered lakes of the McMurdo Dry Valleys harbor many species of cold-adapted algae, including Chlamydomonas sp. UWO241 (UWO241). As a consequence of adaptation to multiple permanent extreme conditions, UWO241 exhibits a remodeled photosynthetic apparatus for maintaining redox poise. One unusual characteristic of UWO241 is the absence of a PSI-associated 77K fluorescence emission under a wide range of growth conditions. This phenotype resembles Fe deficiency in other model organisms such as C. reinhardtii. We hypothesized that adaptation to permanent iron deficiency in its native environment may contribute to this unusual phenotype. We compared the effect of Fe availability on the physiology and photobiology of UWO241 with the model C. reinhardtii as well as a second psychrophilic alga, Chlamydomonas sp. ICE-MDV (ICE). The impacts of a restructured photosynthetic apparatus on the unique Fe-associated phenotype in UWO241 will be discussed.

}, keywords = {LTER-MCM}, url = {http://rave.ohiolink.edu/etdc/view?acc_num=miami1525455621778836}, author = {Cook, Greg and Rachael M. Morgan-Kiss} } @article {1257, title = {Adaptation and acclimation of photosynthetic microorganisms to permanently cold environments}, journal = {Microbial and Molecular Biology Review}, volume = {70}, year = {2006}, month = {03/2006}, pages = {222-252}, abstract = {

Persistently cold environments constitute one of our world\&$\#$39;s largest ecosystems, and microorganisms dominate the biomass and metabolic activity in these extreme environments. The stress of low temperatures on life is exacerbated in organisms that rely on photoautrophic production of organic carbon and energy sources. Phototrophic organisms must coordinate temperature-independent reactions of light absorption and photochemistry with temperature-dependent processes of electron transport and utilization of energy sources through growth and metabolism. Despite this conundrum, phototrophic microorganisms thrive in all cold ecosystems described and (together with chemoautrophs) provide the base of autotrophic production in low-temperature food webs. Psychrophilic (organisms with a requirement for low growth temperatures) and psychrotolerant (organisms tolerant of low growth temperatures) photoautotrophs rely on low-temperature acclimative and adaptive strategies that have been described for other low-temperature-adapted heterotrophic organisms, such as cold-active proteins and maintenance of membrane fluidity. In addition, photoautrophic organisms possess other strategies to balance the absorption of light and the transduction of light energy to stored chemical energy products (NADPH and ATP) with downstream consumption of photosynthetically derived energy products at low temperatures. Lastly, differential adaptive and acclimative mechanisms exist in phototrophic microorganisms residing in low-temperature environments that are exposed to constant low-light environments versus high-light- and high-UV-exposed phototrophic assemblages.

}, keywords = {LTER-MCM, Biggie}, doi = {10.1128/​MMBR.70.1.222-252.2006}, author = {Rachael M. Morgan-Kiss and John C. Priscu and Pocock, T and Gudynaite-Savitch, L and Norman P.A. Huner} }