Journal
ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY
Volume 174, Issue -, Pages 484-490Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ecoenv.2019.03.004
Keywords
Rhodotorula mucilaginosa; EPS; Polysaccharides; Proteins; GSH
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Funding
- National Key R&D Program of China [2018YFD0500201]
- National Natural Science Foundation of China [41671256]
- National Program on Key Basic Research Project [2015CB150504]
- Fundamental Research Funds for the Central Universities [KYZ201712]
- Top-notch Academic Programs Project of Jiangsu Higher Education Institutions [PPZY2015A061]
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Microorganisms have been widely applied to heavy metal adsorption due to their strong secretion of extra cellular polymeric substances (EPS). This study explored the responses of Rhodotorula mucilaginosa (R1, a red yeast with substantial EPS supply) under Pb stress. The maximum sorption of Pb cations by R1 was similar to 650 mg/L. In particular, despite the declined microbial biomass, the total Pb sorption after incubation was actually elevated in the solution with high Pb concentration. At 0-1000 mg/L Pb(NO3)(2) level, the longitudinal sizes of the yeast capsules increased from 2.04 to 2.90 mu m. At 1500 mg/L, however, the survived yeast started to lose the membrane integrity of the cells. Meanwhile, the percentages of organic carbon contents of EPS decreased from 40% to 33% when the Pb(NO3)(2) concentration raised to 2500 mg/L, confirming the incorporation of Pb2+ cations into the fungal EPS during the sorption. For the survived R1 cells, function of polysaccharides to resist Pb toxicity only worked at extremely high Pb(NO3)(2) levels (> = 1500 mg/L). In contrast, proteins showed continuously enhanced ability to resist Pb toxicity, consistent with their increasing content (per cell) in the EPS. Moreover, ATR-IR spectra showed that the intensity of amide II peak at 1540 cm(-1) was significantly increased, indicating elevated glutathione (GSH) in EPS. This suggested that GSH could be the critical Pb-binding component in EPS proteins. This study hence elucidated roles of polysaccharides and proteins in EPS under the toxicity caused by heavy metals.
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