title: Importance of extracellular proteins in maintaining structural integrity of aerobic granules.
abstract: Aerobic granules developed through self-immobilization of microorganisms are compact and structured microbial consortia embedded in a matrix of extracellular polymeric substances (EPS). This study investigated the contribution of extracellular proteins (PN) to maintaining the structural integrity of aerobic granule. It was found that hydrolysis of PN induced by Proteinase K led to significant disintegration of aerobic granules, whereas a substantial reduction of extracellular polysaccharides (PS) was also observed. It was proposed that hydrolysis of extracellular proteins present in the EPS matrix of aerobic granules led to collapse of the EPS matrix, and subsequent disintegration of aerobic granule. These suggested that extracellular proteins would be essential for maintaining structural stability of EPS matrix of aerobic granules. In addition, it was revealed that production of signaling molecules, such as autoinducer-2 (AI-2) and N-acyl homoserine lactones (AHLs) was also inhibited probably due to hydrolysis of quorum sensing receptor proteins by Proteinase K. This in turn provided an additional explanation for the observed Proteinase K-triggered dispersal of aerobic granules.
authors.affiliation: Division of Environmental and Water Resources Engineering, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore.
authors.forename: Yanghui
authors.initials: Y
authors.lastname: Xiong
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
mesh_terms: D054742:Acyl-Butyrolactones / Q000378:metabolism; D000332:Aerobiosis; D018441:Biofilms / Q000254:growth & development; D019149:Bioreactors / Q000382:microbiology; D018914:Cells, Immobilized / Q000378:metabolism; D019286:Endopeptidase K / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D006714:Homoserine / Q000031:analogs & derivatives / Q000378:metabolism; D007783:Lactones / Q000378:metabolism; D059013:Microbial Consortia / Q000502:physiology*; D011134:Polysaccharides / Q000378:metabolism; D053038:Quorum Sensing / Q000502:physiology
chemical_list: D054742:Acyl-Butyrolactones; D016326:Extracellular Matrix Proteins; D007783:Lactones; C091088:N-octanoylhomoserine lactone; D011134:Polysaccharides; D006714:Homoserine; D019286:Endopeptidase K
keywords: Aerobic granules; Autoinducer-2; Extracellular polysaccharides; Extracellular proteins; N-acyl homoserine lactones; Proteinase K