title: Microgradients in bacterial colonies: use of fluorescence ratio imaging, a non-invasive technique.
abstract: Fluorescence ratio imaging is a non-invasive technique for studying the formation of microgradients in immobilised bacterial colonies. These gradients can be quantified easily when combined with the gel cassette system designed at the Institute of Food Research, Norwich, UK. Colonies of Lactobacillus curvatus were observed using this technique and relevant pH gradients were present when the colonies reached a diameter of about 100 microm. These pH gradients were due to production of lactic acid by L. curvatus cells in the colonies. The spatial resolution of the images was about 1.5 microm (scale of bacterial cells) and therefore very suitable for observing local effects in colonies which ranged in sizes from 1 to 500 microm.
authors.affiliation: Department of Food Technology and Nutritional Sciences, Wageningen Agricultural University, The Netherlands.
authors.forename: P K
authors.initials: PK
authors.lastname: Malakar
authors.forename: T F
authors.initials: TF
authors.lastname: Brocklehurst
authors.forename: A R
authors.initials: AR
authors.lastname: Mackie
authors.forename: P D
authors.initials: PD
authors.lastname: Wilson
authors.forename: M H
authors.initials: MH
authors.lastname: Zwietering
authors.forename: K
authors.initials: K
authors.lastname: van't Riet
mesh_terms: D001431:Bacteriological Techniques; D006863:Hydrogen-Ion Concentration; D007091:Image Processing, Computer-Assisted; D007778:Lactobacillus / Q000378:metabolism*; D008856:Microscopy, Fluorescence / Q000295:instrumentation / Q000379:methods*