title: Dynamic light scattering: A fast and reliable method to analyze bacterial growth during the lag phase.
abstract: A comparison between plate counting (PC) and dynamic light scattering (DLS) is reported. PC is the standard technique to determine bacterial population as a function of time; however, this method has drawbacks, such as the cumbersome preparation and handling of samples, as well as the long time required to obtain results. Alternative methods based on optical density are faster, but do not distinguish viable from non-viable cells. These inconveniences are overcome by using DLS. Two different bacteria strains were considered: Escherichia coli and Staphylococcus aureus. DLS was performed at two different illuminating conditions: continuous and intermittent. By the increment of particle size as a function of time, it was possible to observe cell division and the formation of aggregates containing very few bacteria. The scattered intensity profiles showed the lag phase and the transition to the exponential phase of growth, providing a quantity proportional to viable bacteria concentration. The results revealed a clear and linear correlation in both lag and exponential phase, between the Log10(colony-forming units/mL) from PC and the Log10of the scattered intensity Isfrom DLS. These correlations provide a good support to use DLS as an alternative technique to determine bacterial population.
authors.affiliation: Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, 76230 Querétaro, Qro., Mexico.
authors.forename: Susana
authors.initials: S
authors.lastname: Vargas
authors.affiliation: CONACyT, - Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, 76230 Querétaro, Qro., Mexico. Electronic address: bemillan@fata.unam.mx.
authors.forename: Blanca E
authors.initials: BE
authors.lastname: Millán-Chiu
authors.affiliation: Facultad de Química, Universidad Autónoma de Querétaro, C.U., Cerro de las Campanas s/n, 76010 Querétaro, Qro., Mexico.
authors.forename: Sofía M
authors.initials: SM
authors.lastname: Arvizu-Medrano
authors.affiliation: Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, 76230 Querétaro, Qro., Mexico. Electronic address: loske@fata.unam.mx.
authors.forename: Achim M
authors.initials: AM
authors.lastname: Loske
authors.affiliation: Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, 76230 Querétaro, Qro., Mexico.
authors.forename: Rogelio
authors.initials: R
authors.lastname: Rodríguez
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D001431:Bacteriological Techniques / Q000379:methods*; D015169:Colony Count, Microbial / Q000379:methods; D003470:Culture Media; D000067493:Dynamic Light Scattering / Q000295:instrumentation / Q000379:methods*; D004926:Escherichia coli / Q000254:growth & development; D050296:Microbial Viability; D013211:Staphylococcus aureus / Q000254:growth & development
chemical_list: D003470:Culture Media
keywords: Dynamic light scattering; Escherichia coli; Lag phase of growth; Plate counting; Staphylococcus aureus