title: Effects of D-amino acids and norspermidine on the disassembly of large, old-aged microbial aggregates.
abstract: The increasing threat of microbial aggregates in many fields highlights the need to develop methods to promote their disassembly. This study investigated the coupled effects of d-tyrosine (d-Tyr) and norspermidine on the disassembly of a type of old-aged (more than 6 months), large (about 900 μm) microbial aggregate formed by mixed culture. Results showed that d-Tyr and norspermidine acting together effectively triggered the disassembly of microbial aggregates, with disassembly ratio enhanced by 30-164% compared to the control at the concentration of 50-500 μM of d-Tyr and norspermidine. d-Tyr and norspermidine reduced the content of extracellular protein and polysaccharide in microbial aggregates and altered the matrix structure of extracellular polymeric substances as confirmed by a confocal laser scanning microscope. The microbial aggregates lost stability after treatment with d-Tyr and norspermidine as could be seen from the increase in surface negative charge and decrease in cell hydrophobicity. Fourier transform infrared spectroscopy analysis revealed that norspermidine could directly interact with polysaccharide and caused the disappearance of an IR band at 1152 cm(-1) that may be correlated with the functional group C-O-C. Overall, the combined application of d-amino acids and norspermidine offers an effective approach to disassemble large and resistant microbial aggregates.
authors.affiliation: Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, No. 19, Xinjiekouwai Street, Haidian District, Beijing 100875, China.
authors.forename: Xiurong
authors.initials: X
authors.lastname: Si
authors.affiliation: Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, No. 19, Xinjiekouwai Street, Haidian District, Beijing 100875, China. Electronic address: xchquan@bnu.edu.cn.
authors.forename: Xiangchun
authors.initials: X
authors.lastname: Quan
authors.affiliation: Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA.
authors.forename: Qilin
authors.initials: Q
authors.lastname: Li
authors.affiliation: Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, No. 19, Xinjiekouwai Street, Haidian District, Beijing 100875, China.
authors.forename: Yachuan
authors.initials: Y
authors.lastname: Wu
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism*; D018533:Biomass; D001704:Biopolymers / Q000096:biosynthesis; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions / Q000187:drug effects; D010316:Particle Size; D011134:Polysaccharides / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013095:Spermidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013997:Time Factors; D014443:Tyrosine / Q000494:pharmacology*
chemical_list: D001704:Biopolymers; D011134:Polysaccharides; D014443:Tyrosine; C006760:norspermidine; D013095:Spermidine
keywords: Disassembly; Extracellular polymeric substances; Microbial aggregates; Norspermidine; d-tyrosine