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There is a great need for rapid detection of bio-hazardous species particularly in applications to food safety and biodefense.
It has been recently demonstrated that the colonies of various bio-species could be rapidly detected using
culture-specific and reproducible patterns generated by scattered non-coherent light. However, the method heavily relies
on a digital pattern recognition algorithm, which is rather complex, requires substantial computational power and is
prone to ambiguities due to shift, scale, or orientation mismatch between the analyzed pattern and the reference from the
library. The improvement could be made, if, in addition to the intensity of the scattered optical wave, its phase would be
also simultaneously recorded and used for the digital holographic pattern recognition. In this feasibility study the
research team recorded digital Gabor-type (in-line) holograms of colonies of micro-organisms, such as Salmonella with
a laser diode as a low-coherence light source and a lensless high-resolution (2.0x2.0 micron pixel pitch) digital image
sensor. The colonies were grown in conventional Petri dishes using standard methods. The digitally recorded holograms
were used for computational reconstruction of the amplitude and phase information of the optical wave diffracted on the
colonies. Besides, the pattern recognition of the colony fragments using the cross-correlation between the digital
hologram was also implemented. The colonies of mold fungi Altenaria sp, Rhizophus, sp, and Aspergillus sp have been
also generating nano-colloidal silver during their growth in specially prepared matrices. The silver-specific plasmonic
optical extinction peak at 410-nm was also used for rapid detection and growth monitoring of the fungi colonies.
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