title: Mapping bacterial surface population physiology in real-time: infrared spectroscopy of Proteus mirabilis swarm colonies.
abstract: We mapped the space-time distribution of stationary and swarmer cells within a growing Proteus mirabilis colony by infrared (IR) microspectroscopy. Colony mapping was performed at different positions between the inoculum and the periphery with a discrete microscope-mounted IR sensor, while continuous monitoring at a fixed location over time used an optical fiber based IR-attenuated total reflection (ATR) sensor, or "optrode." Phenotypes within a single P. mirabilis population relied on identification of functional determinants (producing unique spectral signals) that reflect differences in macromolecular composition associated with cell differentiation. Inner swarm colony domains are spectrally homogeneous, having patterns similar to those produced by the inoculum. Outer domains composed of active swarmer cells exhibit spectra distinguishable at multiple wavelengths dominated by polysaccharides. Our real-time observations agree with and extend earlier reports indicating that motile swarmer cells are restricted to a narrow (approximately 3 mm) annulus at the colony edge. This study thus validates the use of an IR optrode for real-time and noninvasive monitoring of biofilms and other bacterial surface populations.
authors.affiliation: Laboratoire des Polymères, Propriétés aux Interfaces et Composites, Université de Bretagne-Sud, Campus de Tohannic, BP573, 56017 Vannes Cedex, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Keirsse
authors.forename: Elodie
authors.initials: E
authors.lastname: Lahaye
authors.forename: Anthony
authors.initials: A
authors.lastname: Bouter
authors.forename: Virginie
authors.initials: V
authors.lastname: Dupont
authors.forename: Catherine
authors.initials: C
authors.lastname: Boussard-Plédel
authors.forename: Bruno
authors.initials: B
authors.lastname: Bureau
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Adam
authors.forename: Valérie
authors.initials: V
authors.lastname: Monbet
authors.forename: Olivier
authors.initials: O
authors.lastname: Sire
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D015169:Colony Count, Microbial / Q000379:methods*; D003199:Computer Systems; D016002:Discriminant Analysis; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D018613:Microscopy, Confocal / Q000295:instrumentation* / Q000379:methods; D055100:Optical Fibers; D011513:Proteus mirabilis / Q000166:cytology* / Q000302:isolation & purification / Q000502:physiology*; D013055:Spectrophotometry, Infrared / Q000295:instrumentation* / Q000379:methods