Dinoflagellates are an extremely morphologically and ecologically diverse group of organisms. Dinoflagellates are mainly characterized by their two dissimilar flagella (whiplike appendages used for swimming), with a transverse flagella that beats to the side of the cell and a conventional flagella that beasts posteriorly, and a cell covering called an amphiesma or cortex (Figure 1a). Many dinoflagellates, such as Karenia brevis in particular, are capable of filling multiple ecological roles as they are capable of auxotrophic heterotrophy (meaning they can utilize both organic and inorganic compounds as food), as well as also possessing chloroplasts allowing them to perform photosynthesis as well (Figure 1b) [Vargo 2009]. Karenia brevis is most well-known for its role in harmful algae blooms (HABs) and is one of the primary organisms responsible for the phenomena known as ‘red tides’ seen off the Florida coast [Ross et al. 2010]. One of the reasons HABs of Karenia brevis are so disruptive to ecosystems is due to their ability to produce brevetoxins. Brevetoxins are neurotoxins produced by dinoflagellates such as Karenia brevis, and when their populations bloom during HABs, the concentration of these toxins can reach harmful and potentially deadly levels resulting in fish kills, coral death, and even human illness [Baden 1989]. Currently, it is not currently known for certain why Karenia brevis and other dinoflagellates produce brevetoxins. One of the more recent debates revolves around the hypothesis that brevetoxins are produced in response to osmotic stress felt by these organisms [Errera & Campbell 2011; Sunda et al. 2013].
Figure 1. Karenia brevis. Scanning election micrograph (a + c) of dorsal and ventral views highlights the two flagella and characteristic apical groove. Light microscopy (b + d) of Karenia brevis ventral view highlighting organelles (particularly chloroplasts). Scale bars, 10um. Figure adapted from [Haywood et al. 2004].
Baden, D. G. (1989). Brevetoxins: unique polyether dinoflagellate toxins. The FASEB journal, 3(7), 1807-1817.
Errera, R. M., & Campbell, L. (2011). Osmotic stress triggers toxin production by the dinoflagellate Karenia brevis. Proceedings of the National Academy of Sciences, 108(26), 10597-10601.
Haywood, A. J., Steidinger, K. A., Truby, E. W., Bergquist, P. R., Bergquist, P. L., Adamson, J., & Mackenzie, L. (2004). COMPARATIVE MORPHOLOGY AND MOLECULAR PHYLOGENETIC ANALYSIS OF THREE NEW SPECIES OF THE GENUS KARENIA (DINOPHYCEAE) FROM NEW ZEALAND 1. Journal of Phycology, 40(1), 165-179.
Ross, C., Ritson-Williams, R., Pierce, R., Bullington, J. B., Henry, M., & Paul, V. J. (2010). Effects of the Florida red tide dinoflagellate, Karenia brevis, on oxidative stress and metamorphosis of larvae of the coral Porites astreoides. Harmful Algae, 9(2), 173-179.
Sunda, W. G., Burleson, C., Hardison, D. R., Morey, J. S., Wang, Z., Wolny, J., ... & Van Dolah, F. M. (2013). Osmotic stress does not trigger brevetoxin production in the dinoflagellate Karenia brevis. Proceedings of the National Academy of Sciences, 110(25), 10223-10228.
Vargo, G. A. (2009). A brief summary of the physiology and ecology of Karenia brevis Davis (G. Hansen and Moestrup comb. nov.) red tides on the West Florida Shelf and of hypotheses posed for their initiation, growth, maintenance, and termination. Harmful Algae, 8(4), 573-584.
by Adam Solon
While hiking in the mountains you may come across snow that appears red or pink. This phenomenon, commonly called “red” or “watermelon” snow, is the result of microbial organisms known as algae. Algae inhabit a variety of environments – freshwater, saltwater, soil – and are single celled organisms that, like plants, use the sun for energy (photosynthesis). A particular type of algae, the snow algae, are capable of living in snow or ice during the melt season in alpine and polar environments across the Earth (Hoham and Duval, 2000). Our lab encountered them on the high, cold, windswept slopes of the Atacama Andes (Figure 1).
As members of a large group of organisms known as green algae, snow algae have been to date mostly found within the genus Chlamydomonas or genus Cholormonas. Their brilliant red color is a response to the extreme cryospheric environments in which they are found (Figure. 2). In some known species of snow algae, the compound astaxanthin, a secondary metabolite known as a carotenoid, is responsible for the characteristic red pigment (Bidigare et al., 1993). The red pigmentation serves to limit exposure to the higher radiation found in high elevation and polar environments. This has a double effect of limiting cellular damage (Hagen et al., 1993) as well as alleviating major photoinhibition which is the disruption of energy production (Thomas and Duval, 1995).
So, the next time you are out hiking and see some red snow realize there are a multitudes of those little critters hard at work surviving in the cold and painting an otherwise white landscape with a little color.
Bidigare, R. R., Ondrusek, M. E., Kennicutt, M. C., Iturriaga, R., Harvey, H. R., Hoham, R. W., & Macko, S. A. (1993). EVIDENCE A PHOTOPROTECTIVE FOR SECONDARY CAROTENOIDS OF SNOW ALGAE 1. Journal of Phycology, 29(4), 427-434.
Hagen, C. H., Braune, W., & Greulich, F. (1993). Functional aspects of secondary carotenoids in Haematococcus lacustris [Girod] Rostafinski (Volvocales) IV. Protection from photodynamic damage. Journal of Photochemistry and Photobiology B: Biology, 20(2-3), 153-160.
Hoham RW, Duval B (2001) Microbial ecology of snow and fresh-water ice with emphasis on snow algae. In Jones, H. G., Pomeroy, J. W., Walker, D. A., & Hoham, R. W. (Eds.). (2001). Snow ecology: an interdisciplinary examination of snow-covered ecosystems. Cambridge University Press.
Thomas, W. H., & Duval, B. (1995). Sierra Nevada, California, USA, snow algae: snow albedo changes, algal-bacterial interrelationships, and ultraviolet radiation effects. Arctic and alpine research, 27(4), 389-399.
by Michelle Hollenkamp
If you happen across this microbe of the month, it’s unique appearance may cause you to take a step back. Young Hydnellum peckii, commonly called the bleeding tooth fungus, oozes or “bleeds” a thick, red fluid through pores on the cap of its fruiting body. The droplets are referred to as guttules. As if the characteristic isn’t scary enough, H.peckii have 2-5mm spines, similar to teeth, on the underside of their cap. As these fungi mature, they become less descript becoming turning gray or brown in color.
H.peckii belong to the Aphyllophorales order and the Hydnaceae family. They are widely dispersed in Europe and the Pacific Northwest, commonly in association with conifers and can be found among moss and pine litter. They fruit in the summer months as a solitary or fused fruiting bodies. These fungi are mycorrhiza, living in symbiosis with vascular plant roots. Despite their rather unjarring appearance, H.peckii are non-toxic. However, their taste has been described as bitter pepper deeming it inedible. This fungus does have several beneficial uses. The mushroom of H. peckii contains atromentin, which has antibacterial and anticoagulant properties. Additionally, the oozing red “blood” can be used to dye fabrics. Though these species are not found in Colorado, other Hydnellum species can be seen in the Rocky Mountains.
“Bleeding Tooth Fungus.” National Geographic, 2015. <http://www.nationalgeographic.com.au/nature/the-bleeding-tooth-fungus.aspx>
Evenson, Vera Stucky. “Mushrooms of Colorado and the Southern Rocky Mountains.” Big Earth Publishing, 1997.
Holden, Liz. “Scotland’s rare tooth fungi: an introduction to their identification, ecology, and management. Plantlife International, 2008.
by Cliff Bueno de Mesquita
Leohumicola is another genus of fungi that we found frequently in the roots of the alpine cushion plant Silene acaulis (see May post). Unlike Serendipita, which I wrote about last month, Leohumicola are members of the phylum Ascomycota. Not only was Leohumicola one of the more abundant fungi in the Silene plants, it also differed among our various experimental treatments. In addition to sequencing roots of adult Silene plants from Ireland and Colorado, we conducted a greenhouse experiment in which we grew Irish Silene plants in both Irish and Colorado soil, and Colorado Silene plants in both Irish and Colorado soil. Interestingly, Leohumicola was most abundant in Colorado adult Silene plants and Irish seedling Silene plants.
Leohumicola was described as a new genus in 2005, with 4 species (Hambleton et al. 2005). This group of fungi displays a remarkable range of temperature tolerances, as it has been found in high alpine environments as well as heat treated soils. One species, Leohumicola verrucosa (Figure 1) has been isolated from a pharmaceutical plant (Pleione yunnanensis) in China (Chen et al. 2009). Leohumicola have also been reported to associate with plants in the Ericaceae family, and to form ericoid mycorrhizal structures (Bizabani et al. 2016). As discussed in previous posts, mycorrhizae are fungi that associate with plants in a mutualistic relationship in which both parties benefit; the fungus receives carbon from the plant, and the plant receives nutrients from the fungus. Ericoid mycorrhizae are fungi that associate with plants in the Ericaceae family, and are characterized by forming dense coils in the plant cells for nutrient exchange (Figure 2). Researchers reported Leohumicola in commercial blueberry roots, and increased plant growth in plants with the fungus. Thus, it appears that Leohumicola could have beneficial impacts on plant growth, and potentially play a role in the growth of plants outside of the Ericaceae, like our Silene plants (family Caryophyllaceae).
Bizabani, C., Fontenla, S., and Dames, J.F. 2016. Ericoid fungal inoculation of blueberry under commercial production in South Africa. Scientia Horticulturae 209: 173-177.
Chen, J., Meng, Z., Chen, X., Lu, Y., Zhang, F., Li, X, and Guo, S. 2009. Leohumicola, a genus new to China. Mycotaxon 108: 337-340.
Hambleton, S., Nickerson, N.L., and Seifert, K.A. 2005. Leohumicola, a new genus of heat-resistant hyphomycetes. Studies in Mycology 53: 29-52.
by Cliff Bueno de Mesquita
Serendipita is a genus of mycorrhizal fungi from a different lineage than most other mycorrhizae. Remember, a mycorrhizal fungus is one that forms a mutualism with a plant, helping the plant uptake nutrients in exchange for carbon that the plant creates through photosynthesis. Serendipita are in the order Sebacinales, class Agaricomycetes, phylum Basidiomycota. Fungi in the order Sebacinales were originally considered “orchid mycorrhizae”, as they were thought to only associate with orchid plants. However, they have now been found in mosses, ferns, and a variety of other plants including wheat, maize, poplar, and tomato. In our own work, we found that Serendipita was a dominant fungus found inside the roots of the moss campion Silene acaulis, a beautiful arctic-alpine plant with a circumpolar distribution (Figure 1A, 1B). We sequenced the fungal DNA found inside the roots of Silene acaulis from plants at our site in Colorado, as well as from plants from Ireland, in collaboration with a visiting Fulbright scholar Conor Meade, from the University of Maynooth, Ireland. We defined “dominant” as a fungus being in the top 10% most abundant fungi in the roots, and found in over 50% of the individual plants sampled (Delgado-Baquerizo et al. 2018). Serendipita was one of only four known fungal genera that qualified as dominant, so we think it is playing a role in the growth of Silene acaulis.
The genus Serendipita was first described in 1993 (Roberts 1993). One of the species in the genus, Serendipita vermifera, has been shown to increase the growth of switchgrass, which is grown as a bioenergy crop (Ray et al. 2018). Another species, Serendipita indica, was shown to increase the growth of the plant used to make turmeric (Bhola et al. 2017). Researchers are currently working on growing this fungus in large quantities to then add to soil to promote plant growth (Singhal et al. 2017).
Bhola, D., Bajaj, R., Tripathi, S., Varma, A. 2017. Piriformospora indica(Serendipita indica) enhances growth and secondary metabolites in Cucurma longa. In: Varma, A., Prasad, R., Tuteja, N., (eds). Mycorrhiza – Nutrient Uptake, Biocontrol, Ecorestoration. Springer, Cham.
Delgado-Baquerizo, M., Oliverio, A.M., Brewer, T.E., Benavent-González, A., Eldridge, D.J., Bardgett, R.D., Maestre, F.T., Singh, B.K., Fierer, N. 2018. A global atlas of the dominant bacteria found in soil. Science359: 320-325.
Ray, P., Guo, Y., Sun, L., Tang, Y., Craven, K.D., Gilna, P. 2018. Signaling between switchgrass and fungal endosymbionts in the genus Serendipita. https://genomicscience.energy.gov/pubs/2017abstracts/abstractpdfs/73_Gilna_Paul_Ray.pdf
Roberts P. 1993. Exidiopsis species from Devon, including the new segregate genera Ceratosebacina, Endoperplexa, Microsebacina, and Serendipita. Mycological Research. 97 (4): 467–78. doi:10.1016/S0953-7562(09)80135-4.
Singhal, U., Attri, M.K., Varma, A. 2017. Mass cultivation of mycorrhiza-like fungus Piriformospora indica(Serendipita indica) by batch in bioreactor. In: Varma, A., Prasad, R., Tuteja, N. (eds). Mycorrhiza – Function, Diversity, State of the Art. Springer, Cham.
Vohník, M., Pánek, M., Fehrer, J., Selosse, M. 2016. Experimental evidence of ericoid mycorrhizal potential within Serendipitaceae (Sebacinales). Mycorrhiza26(8): 831-846.
by Eli Gendron
One of the greatest challenges sessile (immobile) organisms face is obtaining an adequate supply of food while not being able to actively forage or hunt for it. One way to get around this limitation is to have a motile life stage that is able to actively disperse to other parts of the environment where food might be more abundant (Sousa 1979). Members of the Vorticella genus are an example of ciliates that possess this adaptation, and thrive in a wide variety of freshwater habitats, and even inundated grasslands (Sun et al. 2012; Stout 1984). Ciliates are single-celled organisms that make up their own phylum (Ciliophora), and are characterized by having cilia, or hair-like structures on the outside of their cells. Vorticella species alternate between a free-swimming motile stage known as a telotroch, and a sessile phase known as a trophont, where it forms a contractible stalk that anchors the body to a substrate (Williams and Clamp 2007). The contractible stalk is one example how this genus has adapted to freshwater ecosystems. The stalk has been hypothesized to allow the body to retract closer to the substrate during turbulent conditions or potentially to mix its surroundings in order to obtain food in extremely calm conditions (Ryu et al. 2016, Figure1C).
Vorticella sp. are very effective filter feeders (feeding by straining substances from the water) due to their ability to use their cilia to create currents that direct nearby organic matter directly into their body cavity (Ryu et al. 2016, Figure 1B). Taken together, these adaptations have made Vorticella sp. a target for bioengineering microfluidic devices. Outside of engineering applications Vorticella sp. even have potential applications as biocontrol agents for mosquitos. Patil et al. 2016 found that mosquito larvae that became infected with parasitic a Vorticella sp. saw a 90% reduction in adult emergence. Lastly, Vorticella’s ubiquity in freshwater habitats and their sensitivity to water quality make them excellent candidates for indicators of ecosystem health. For example, Vorticella sp. have been observed thriving in aquatic habitats with high levels of organic matter and low nitrogen cycling capacity (Perez-Uz et al. 2010).
Patil CD, Narkhede CP, Suryawanshi RK, Patil SV. 2016. Vorticella sp: Prospective mosquito biocontrol agent. J Arthropod Borne Dis 10:602–607.
Pérez-Uz B, Arregui L, Calvo P, Salvadó H, Fernández N, Rodríguez E, Zornoza A, Serrano S. 2010. Assessment of plausible bioindicators for plant performance in advanced wastewater treatment systems. Water Res 44:5059–5069.
Ryu S, Pepper RE, Nagai M, France DC. 2017. Vorticella: A protozoan for bio-inspired engineering. Micromachines 8:1–25.
Stout JD. 1984. The protozoan fauna of a seasonally inundated soil under grassland. Soil Biol Biochem 16:121–125.
Sun P, Clamp J, Xu D, Kusuoka Y, Miao W. 2012. Vorticella Linnaeus, 1767 (Ciliophora, Oligohymenophora, Peritrichia) is a Grade not a Clade: Redefinition of Vorticella and the Families Vorticellidae and Astylozoidae using Molecular Characters Derived from the Gene Coding for Small Subunit Ribosomal RN. Protist 163:129–142.
Williams D, Clamp JC. 2007. A molecular phylogenetic investigation of Opisthonecta and related genera (Ciliophora, Peritrichia, Sessilida). J Eukaryot Microbiol 54:317–323.
by Lara Vimercati
Extremophilic (organisms that live in extreme environments) members of the yeast Naganishia (previously classified as the Cryptococcus genus) represent the most abundant eukaryotes (organisms with a nucleus) from some of the harshest ecosystems yet discovered on Earth: the high elevations in dry valleys and slopes of the high Andes (Costello et al. 2009, Lynch et al. 2012, Vimercati et al. 2016). This Naganishia sp. (Phylum Basidiomycota) is most closely related to Cryptococcus friedmannii, which lives on rocks and tolerates extreme droughts, from the Dry Valleys of Antarctica and is also related to some of the dominant microeukaryotes of other extreme polar and glacial regions (Buzzini et al. 2012). Recent studies indicate that Naganishia species from the high Andes are among the most resistant organisms to UV radiation (Pulschen et al. 2015) and our work on a Naganishia strain from the high Andes showed that it is able to grow continuously in liquid culture when exposed to extreme thermal fluctuations. In this experiment we simulated the diurnal freeze-thaw cycles that occur on a continuous basis at elevations above 6000 meters above sea level in the Atacama region cycling up to a high of 30°C during the day and down to a low of -10°C at night, an amplitude of 40°C in a 24-hour period (Vimercati et al. 2016). These studies provide evidence that Naganishia sp. has the capacity to grow during freeze-thaw cycles in the field, and that it may be able to mainly do that during periods of higher soil moisture. Given its unique ability to survive under multiple environmental stressors, Naganishias may be a model organism for astrobiology and studies on stress resistance in eukaryotes, and its adaptive strategies could be crucial as predictive tools in investigating the limits of life.
Figure 1. Exponential growth of the Naganishia sp. isolate (top panel) during freeze-thaw cycles of 27°C to -10°C as measured with data loggers in the growth chamber (bottom panel). Higher absorbance values mean more growth. Temperatures in the actual growth medium were comparable to these in the chamber, but showed a lag of about 1 hour (data not shown). All cultures froze solid every night and completely melted every day. It is not clear from these data if growth was continuous or occurred only during periods of liquid water since all sub-samples were taken when cultures were melted. Each point represents the mean of four replicate cultures (error bars are standard error of the mean).
Buzzini P, Branda E, Goretti M, Turchetti B (2012) Psychrophilic yeasts from worldwide glacial habitats: diversity, adaptation strategies and biotechnological potential. FEMS Microbiol Ecol 82: 217–241.
Costello, E.K., S.R.P. Halloy, S.C. Reed, P. Sowell, S.K. Schmidt. 2009. Fumarole supported islands of biodiversity within a hyperarid, high-elevation landscape on Socompa Volcano, Puna de Atacama, Andes. Appl. Environ. Microbiol. 75: 735-747.
Lynch, R.C., King, A.J., Farías, M.E., Sowell, P., Vitry, C. and Schmidt, S.K., 2012. The potential for microbial life in the highest‐elevation (> 6000 masl) mineral soils of the Atacama region. Journal of Geophysical Research: Biogeosciences, 117(G2).
Pulschen, A.A., Rodrigues, F., Duarte, R.T., Araujo, G.G., Santiago, I.F., Paulino‐Lima, I.G., Rosa, C.A., Kato, M.J., Pellizari, V.H. and Galante, D., 2015. UV‐resistant yeasts isolated from a high‐altitude volcanic area on the Atacama Desert as eukaryotic models for astrobiology. MicrobiologyOpen, 4(4), pp.574-588.
Vimercati L, Hamsher S, Schubert Z, Schmidt SK. 2016. Growth of a high-elevation Cryptococcus sp. during extreme freeze-thaw cycles. Extremophiles. 20:579–588.
by Pacifica Sommers
Tardigrades, also known as “water bears” or “moss piglets,” are microscopic animals that have captured the public’s imagination in such forums as the new Star Trek: Discovery television series (https://www.space.com/38477-star-trek-discovery-mudd-ies-up-tardigrade-science.html) for their ability to survive the radiation of space (Rebecchi et al. 2009). Although most microbiologists would consider them microfauna, or microscopic animal life, rather than microbes strictly speaking, we are including them here because they are invisible to the naked eye. You typically need a microscope to see these creatures less than one millimeter long.
However, like humans rather than bacteria, tardigrades have nuclei in their cells, and are even multicellular – that is, they are made up of many cells (Nichols 2005). Tardigrades have a piercing mouth part that some herbivorous species use to eat mosses or plant-like algae, and other predatory species use to eat microscopic animals such as nematodes or rotifers (Nichols 2005, Hohberg & Traunspurger 2009).
When placed on a glass or plastic petri dish or slide to view under a microscope, tardigrades have a hard time gaining traction, and thus look like they are running in place, moving slowly: hence the name tardigrade, which means “slow stepper.” However, if they have sand or something sticky in a petri dish like agar, they can walk somewhat like an eight-legged caterpillar might. They live in many environments around the world, especially in mosses, in leaf litter, in the nutrient-poor soils of polar and alpine environments, and can even be found in the ocean (Nichols 2005).
The tardigrades pictured here were extracted from cryoconite holes, or small mud puddles, on Antarctic glaciers.
Hohberg, K., & Traunspurger, W. (2009). Foraging theory and partial consumption in a tardigrade–
nematode system. Behavioral Ecology, 20(4), 884-890.
Nichols, P. B. (2005). Tardigrade evolution and ecology. Dissertation, University of South Florida.
Rebecchi, L., Altiero, T., Guidetti, R., Cesari, M., Bertolani, R., Negroni, M., & Rizzo, A. M. (2009).
Tardigrade resistance to space effects: first results of experiments on the LIFE-TARSE mission on FOTON-M3 (September 2007). Astrobiology, 9(6), 581-591.
by Cliff Bueno de Mesquita
Phialophora is a genus of fungus containing taxa capable of a variety of functions. They can be parasitic on fruits and humans, saprotrophic (decompose dead plant material), or mutualistic with plants. At our field site at Niwot Ridge in the Colorado Rocky Mountains, Phialophora was one of the most abundant fungi we found living inside of plant roots. We found DNA sequences of this genus in 126 of 177 plants that we sampled. Before extracting the DNA from plant roots, we washed them in ethanol and bleach to sterilize the root surface; thus we believe this fungus is inhabiting the inside of plant roots and directly interacting with the plant.
We are interested in this fungus because it is a dark septate fungus that can benefit plant growth. For example, Newsham (1999) found that the fungus Phialophora graminicola benefited the growth of its host plant. We’ve known that this group of fungi lives in the alpine for a while now. A former student in the lab, Chris Schadt, found a fungus in this genus (Phialophora gregata) inside of an alpine plant back in 2001 (Fig. 1). Interestingly, the sequences from our 2016 survey at Niwot were closely related to Phialophora that were found inside of moss tissues on King George Island in Antarctica, which suggests that this genus is widespread geographically. We are currently trying to culture this fungus to isolate it and conduct experiments with it in the greenhouse to see if this particular strain benefits plant growth.
Newsham, K. K. 1999: Phialophora graminicola , a dark septate fungus, is a beneficial associate of the grass Vulpia ciliata ssp. ambigua. New Phytologist, 144: 517–524, doi: https://doi.org/10.1046/j.1469-8137.1999.00537.x.
Newsham, K. K. 2011: A meta-analysis of plant responses to dark septate root endophytes. New Phytologist, 190: 783–793, doi: https://doi.org/10.1111/j.1469-8137.2010.03611.x.
Schadt, C. W., Mullen, R. B., and Schmidt, S. K. 2001: Isolation and phylogenetic identification of a dark-septate fungus associated with the alpine plant Ranunculus adoneus. New Phytologist, 150: 747–755.
Yu, N. H., Kim, J. A., Jeong, M.-H., Cheong, Y. H., Hong, S. G., Jung, J. S., … Hur, J.-S. 2014: Diversity of endophytic fungi associated with bryophyte in the maritime Antarctic (King George Island). Polar Biology, 37: 27–36, doi: https://doi.org/10.1007/s00300-013-1406-5.
by Dorota Porazinska
Mortierella species are aseptate, filamentous soil fungi belonging to the order of Mortierellales of the Zygomycota phylum. Among the 70+ described species, most are commonly found in soil. As saprophytic organisms (those that live on dead or decomposing matter), they can be associated with a multitude of substrate sources including plant litter. A unique feature of Mortierella is that some species are known to be exceptionally well adapted to living under very cold conditions typical of arctic, Antarctic and high alpine snow-covered soils. As psychrophilic (cold-loving), they can grow at near- or even below-freezing temperatures and survive freeze-thaws cycles and desiccation. To tolerate cold, they employ physiological mechanisms that diminish the possibility of cellular water to freeze, crystalize, and rupture cell membranes. The most common mechanisms include production of trehalose and cryoprotectant sugars that stabilize membranes, glycerol and mannitol that maintain turgor pressure, unsaturated fatty acids that maintain fluidity of membrane structures, and antifreeze proteins that may slow the growth of ice crystals.
At our field site at Niwot Ridge in the Colorado Rocky Mountains, Mortierella species can be easily observed as white mats, also known as “snow molds”, that quickly appear at the edges of receding snow banks in the spring time. Their incredible fast growth rates have been attributed to their ability to rapidly exploit a fresh flush of nutrients stored in soil and water from melting snow. However, as soon snow is gone, they disappear as fast as they appeared. In a recent survey of soil communities from a range of soil habitats spanning bare to increasingly vegetated, the abundance of Mortierella spp. declined where plant communities have become more established. Because increasing incidence of plants in this landscape reflects diminishing snow cover likely due to climate warming, the future of cold-loving Mortierella spp. lies in “hands” of surviving snow packs keeping high alpine ecosystems free of vegetation.
Schmidt SK, Wilson KL, Meyer AF, Gebauer MM, King AJ. 2008. Phylogeny of ecophysiology of opportunistic “snow molds” from a subalpine forest ecosystem. Microbial Ecology, 56: 681-687.
Robinson CH. 2001. Cold adaptation in Arctic and Antarctic fungi. New Phytologist, 151: 341-353.