Prospects for Fungal Bioremediation of Acidic Radioactive Waste Sites: Characterization and Genome Sequence of Rhodotorula taiwanensis MD1149

Abstract

Highly concentrated radionuclide waste produced during the Cold War era is stored at US Department of Energy (DOE) production sites. This radioactive waste was often highly acidic and mixed with heavy metals, and has been leaking into the environment since the 1950s. Because of the danger and expense of cleanup of such radioactive sites by physicochemical processes, in situ bioremediation methods are being developed for cleanup of contaminated ground and groundwater. To date, the most developed microbial treatment proposed for high-level radioactive sites employs the radiation-resistant bacterium Deinococcus radiodurans. However, the use of Deinococcus spp. and other bacteria is limited by their sensitivity to low pH. We report the characterization of 27 diverse environmental yeasts for their resistance to ionizing radiation (chronic and acute), heavy metals, pH minima, temperature maxima and optima, and their ability to form biofilms. Remarkably, many yeasts are extremely resistant to ionizing radiation and heavy metals. They also excrete carboxylic acids and are exceptionally tolerant to low pH. A special focus is placed on Rhodotorula taiwanensis MD1149, which was the most resistant to acid and gamma radiation. MD1149 is capable of growing under 66 Gy/h at pH 2.3 and in the presence of high concentrations of mercury and chromium compounds, and forming biofilms under high-level chronic radiation and low pH. We present the whole genome sequence and annotation of R. taiwanensis strain MD1149, with a comparison to other Rhodotorula species. This survey elevates yeasts to the frontier of biology's most radiation-resistant representatives, presenting a strong rationale for a role of fungi in bioremediation of acidic radioactive waste sites.

Transcriptomic analysis reveals the relationship of melanization to growth and resistance to gamma radiation in Cryptococcus neoformans

“…Melanized fungi have generated interest due to their abundance in environments with high levels of background IR, which has raised the possibility of using melanin for radiation protection, or discovering a compound produced by these organisms that could prevent radiation damage or aid in recovery from radiation damage in human tissues (Dadachova et al, 2007;Cordero, 2017;Pacelli et al, 2017). Many fungi, melanized and non-melanized, are also extraordinarily resistant to acute and chronic IR, suggesting that mechanisms for radiation recovery remain to be discovered by characterizing the response to IR in these organisms (Holloman et al, 2007;Jung et al, 2016;Shuryak et al, 2017;Jiang et al, 2018;Tkavc et al, 2018). Previously, the transcriptomic responses of C. neoformans (Jung et al, 2016), W. dermatitidis (Robertson et al, 2012), S. pombe (Watson et al, 2004) and S. cerevisiae (Kimura et al, 2006) to various doses of γ-radiation have been published.…”

The Oleaginous Red YeastRhodotorula/Rhodosporidium: A Factory for Industrial Bioproducts

“…Biosurfactants offer a more environmentally friendly option (biodegradable and petroleum-independent); however, there are a limited number of commercially available biosurfactants, and each one covers only a small portion of the HLB scale. Therefore, in order to expand PEFA coverage on the HLB scale, it was recently published that a new strain of Rhodotorula taiwanensis produced hypoacetylated PEFA compounds compared to those produced by Rhodotorula babjevae [108,109]; the difference in their acetylation profiles resulted in different surface tension of the growth medium, i.e. a different hydrophilic-lipophilic balance.…”

Microbiological and Probiotic Assessment of Yeast Isolated from Wholegrain Millet Sourdoughs

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