title: Whole-cell-based identification of electrochemically active bacteria in microbial fuel cells by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
abstract: BACKGROUND
  Electrochemically active bacteria (EAB) that are capable of producing electricity from renewable biomass and organic wastes have been of particular interest in recent years. Methods for selective enrichment, accurate identification and easy acquisition of EAB fingerprints for phylogenetic characterization would facilitate utilization of these bioenergy-producing species in practical environmental engineering applications.
  
  
  METHODS
  Electricigens/exoelectrogens were selectively enriched from domestic wastewater in a microbial fuel cell (MFC). Whole EAB cell-derived mass spectra were obtained with simple agar incubation for 24 h and subsequent release of proteins by 25% formic acid (FA) and ultrasonication. Mass fingerprints of EAB were obtained by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF-MS) and species-specific analyses were completed by using the Spectral ARchive and Microbial Identification System (SARAMIS).
  
  
  RESULTS
  EAB could be discriminated by clustering of MALDI-TOF/TOF-MS results. Different species in mixtures originating from domestic sewage could be identified unambiguously at 99.90% confidence. Five species, namely Klebsiella oxytoca (K. oxytoca), Comamonas testosterone (C. testosterone), Pseudomonas putida (P. putida), Klebsiella pneumonia (K. pneumonia) and Raoultella ornithinolytica (R. ornithinolytica), that are known to be of clinical significance, were found to be enriched in MFCs and determined as high power-producing species. By using an agglomerative clustering algorithm to compute spectral similarity and diversity, a dendrogram was constructed to illustrate the phylogenetic relationships for EAB on the basis of mass spectral analyses.
  
  
  CONCLUSIONS
  An integrated method based on MFC-enrichment, agar-cultivation and MALDI-TOF/TOF-MS identification of whole-cell-extracted proteins has been proved to be a simple, rapid and reliable approach for rapid identification and routine inspection of EAB. Mixed phyla can be analyzed at species level to provide phylogenetic information on the highly efficient bacteria generating electricity from domestic wastewater.
authors.affiliation: Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 117543, Singapore.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 117543, Singapore.
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, 119077, Singapore.
authors.forename: Linke
authors.initials: L
authors.lastname: Lai
authors.affiliation: Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 117543, Singapore.|NUS Environmental Research Institute, National University of Singapore, Singapore, 117411, Singapore.
authors.forename: Sam Fong Yau
authors.initials: SF
authors.lastname: Li
mesh_terms: D001419:Bacteria / Q000737:chemistry* / Q000145:classification / Q000302:isolation & purification; D015373:Bacterial Typing Techniques / Q000379:methods; D001674:Bioelectric Energy Sources / Q000382:microbiology*; D004867:Equipment Design; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D062065:Wastewater / Q000382:microbiology*
chemical_list: D062065:Wastewater