title: Biophysical modeling of forward scattering from bacterial colonies using scalar diffraction theory.
abstract: A model for forward scattering from bacterial colonies is presented. The colonies of interest consist of approximately 10(12) - 10(13) individual bacteria densely packed in a configuration several millimeters in diameter and approximately 0.1-0.2 mm in thickness. The model is based on scalar diffraction theory and accounts for amplitude and phase modulation created by three macroscopic properties of the colonies: phase modulation due to the surface topography, phase modulation due to the radial structure observed from some strains and species, and diffraction from the outline of the colony. Phase contrast and confocal microscopy were performed to provide quantitative information on the shape and internal structure of the colonies. The computed results showed excellent agreement with the experimental scattering data for three different Listeria species: Listeria innocua, Listeria ivanovii, and Listeria monocytogenes. The results provide a physical explanation for the unique and distinctive scattering signatures produced by colonies of closely related Listeria species and support the efficacy of forward scattering for rapid detection and classification of pathogens without tagging.
authors.affiliation: School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47906, USA. ebae@purdue.edu
authors.forename: Euiwon
authors.initials: E
authors.lastname: Bae
authors.forename: Padmapriya P
authors.initials: PP
authors.lastname: Banada
authors.forename: Karleigh
authors.initials: K
authors.lastname: Huff
authors.forename: Arun K
authors.initials: AK
authors.lastname: Bhunia
authors.forename: J Paul
authors.initials: JP
authors.lastname: Robinson
authors.forename: E Daniel
authors.initials: ED
authors.lastname: Hirleman
mesh_terms: D000465:Algorithms; D018407:Bacterial Physiological Phenomena; D015373:Bacterial Typing Techniques; D001703:Biophysics / Q000379:methods*; D015169:Colony Count, Microbial; D005516:Food Microbiology; D007834:Lasers; D008087:Listeria / Q000378:metabolism*; D008089:Listeria monocytogenes / Q000378:metabolism; D018613:Microscopy, Confocal; D008858:Microscopy, Phase-Contrast; D015233:Models, Statistical; D055095:Optics and Photonics; D013045:Species Specificity; D013499:Surface Properties