(689f) Characterization of Bacterial Spore Surfaces Using Nanomechanical Mapping

Several biochemical signatures have been developed that can differentiate bacterial pathogens (and, potentially, the laboratory of origin). However, most require significant amounts of sample (>1x10⁹ cells), which prohibits their use in analyzing biocrime evidence. New systems are needed for the detection and characterization of samples with traces of cells. To address this need, this study developed a means of characterizing bacterial spore surfaces for determining forensically-relevant aspects of an organism’s growth environment at the single cell level. Specifically, the morphology of the cell surface was investigated using nanomechanical mapping to obtain mechanical “signatures” to distinguish different strains and species. Cultures of Bacillus cereus spores, a structural and chemical analog for Bacillus anthracis and different strains of B. cereus (14579 and T-strain) were grown in sporulating culture medium and analyzed using Atomic Force Microscopy (AFM) based nanoindentation. An image recognition based algorithm was used to classify the maps obtained. Results showed that the topography of the spore could be compared by considering the nanomechanical “signatures” and morphologies of the different spores. Since forensic evidence often contains trace quantities of material, the use of AFM in identifying phenotypic differences of Bacillus spores batch cultured in various production conditions can be a novel technique for the attribution of pathogens.