Effects of irradiation and pH on fluorescence properties and flocculation of extracellular polymeric substances from the cyanobacterium Chroococcus minutus.
Microbial extracellular polymeric substances (EPS) may flocculate or be decomposed when environmental factors change, which significantly influences nutrient cycling and transport of heavy metals. However, little information is available on the stability of EPS in natural environments. Fluorescence and flocculation properties of EPS from Chroococcus minutus under different irradiation and pH conditions were studied. Two aromatic protein-like fluorescence peaks and one tyrosine protein-like peak were identified from the excitation-emission-matrix (EEM) fluorescence spectra of EPS. UVB (ultraviolet B) and solar irradiation increased the fluorescence intensity of all the three peaks while UVC (ultraviolet C) irradiation had little effect. EPS formed unstable flocs after exposure to UV (ultraviolet) irradiation and formed stable flocs under solar irradiation. EPS were prone to flocculation under highly acidic conditions and minimal fluorescence of peaks was observed. The fluorophores in EPS were relatively stable under neutral and alkaline conditions. These findings are helpful for understanding the behavior of EPS in aquatic environments and their role in biogeochemical cycles of the elements.
Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
Wenjuan
W
Song
Xinjiang Academy of Environmental Protection Sciences, Urumqi, Xinjiang 830011, China.
Chenxi
C
Zhao
Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
Shuyong
S
Mu
Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China. Electronic address: panxl@ms.xjb.ac.cn.
Xiangliang
X
Pan
Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China. Electronic address: zhang-daoyong@163.com.
Daoyong
D
Zhang
Department of Zoology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
Fahad A
FA
Al-Misned
Department of Zoology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia; Department of Zoology, Faculty of Life and Earth Science, Rajshahi University, Rajshahi 6205, Bangladesh.
M Golam
MG
Mortuza
D002462:Cell Membrane / Q000737:chemistry*; D000458:Cyanobacteria / Q000737:chemistry*; D005110:Extracellular Space / Q000737:chemistry; D005427:Flocculation / Q000528:radiation effects; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000737:chemistry; D011108:Polymers / Q000737:chemistry* / Q000302:isolation & purification / Q000528:radiation effects; D014466:Ultraviolet Rays
D019216:Metals, Heavy; D011108:Polymers
Cyanobacteria; EEM fluorescence spectroscopy; Fluorophores; Heavy metals; Nutrient cycles