title: A new microtitre plate screening method for evaluating the viability of aerobic respiring bacteria in high surface biofilms.
abstract: OBJECTIVE
  It is difficult to determine the effects of bactericidal compounds against bacteria in a biofilm because classical procedures for determining cell viability require several working days, multiple complicated steps and are frequently only applicable to cells in suspension. We attempt to develop a compact, inexpensive and versatile system to measure directly the extent of biofilm formation from water systems and to determine the viability of respiring bacteria in high surface biofilms.
  
  
  RESULTS
  It has been reported that the reduction of tetrazolium sodium salts, such as XTT (sodium 3,3'-[1-[(phenylamino)carbonyl]-3,4-tetrazolium]Bis(4-methoxy)-6-nitro)benzene sulfonic acid hydrate), during active bacterial metabolism can be incorporated into a colorimetric method for quantifying cell viability. XTT is reduced to a soluble formazan compound during bacterial aerobic metabolism such that the amount of formazan generated is proportional to the bacterial biomass.
  
  
  CONCLUSIONS
  We show here, for the first time, that this colorimetric approach can be used to determine the metabolic activity of adherent aerobic bacteria in a biofilm as a measure of cell viability. This technique has been used to estimate viability and proliferation of bacteria in suspension, but this is the first application to microbial communities in a real undisturbed biofilm.
  
  
  CONCLUSIONS
  This simple new system can be used to evaluate the complex biofilm community without separating the bacteria from their support. Thus, the results obtained by this practice may be more representative of the circumstances in a natural system, opening the possibility to multiple potential applications.
authors.affiliation: Laboratori de Microbiologia Sanitaria i Mediambiental (MSM-Lab) & Aquasost - UNESCO Chair in Sustainability, Universitat Politècnica de Catalunya (UPC), Terrassa, Barcelona, Spain.
authors.forename: L M
authors.initials: LM
authors.lastname: Pérez
authors.forename: B L
authors.initials: BL
authors.lastname: Alvarez
authors.forename: F
authors.initials: F
authors.lastname: Codony
authors.forename: M
authors.initials: M
authors.lastname: Fittipaldi
authors.forename: B
authors.initials: B
authors.lastname: Adrados
authors.forename: G
authors.initials: G
authors.lastname: Peñuela
authors.forename: J
authors.initials: J
authors.lastname: Morató
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism; D018407:Bacterial Physiological Phenomena / Q000187:drug effects*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D003124:Colorimetry / Q000379:methods; D008403:Mass Screening / Q000379:methods*; D008826:Microbial Sensitivity Tests / Q000379:methods; D050296:Microbial Viability / Q000187:drug effects*; D013778:Tetrazolium Salts / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D013778:Tetrazolium Salts; C059087:2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide