Traditional biological forensics centers on biological component identification and genoytping. Additional information however is necessary to identify potential culture media, preparation methods, and purification processes used. We are developing a variety of chemical analysis tools for trace impurities and residual materials identification. For example, the identification of agar polymer residual on bacterial spores indicates they were sporulated on agar plates instead of in broth solution. In addition, the identification of certain trace metals indicate a growth media recipe where particular metals are added to the recipe over others that are purely organic in nature. Preliminary development of several mass spectrometric methods to identify residual components and sample impurities of forensic value will be presented.
A controlled sample set with replicate cultures of Bacillus spores from three different media recipes on agar plates and in broth were prepared and analyzed by an array of mass spectrometric tools. Data from these analytical tools are extracted and integrated for optimal information.
Signatures of biological sample preparation methods were developed and evaluated for forensic value. Signatures such as the observation of ions representative of the agar polymer are direct evidence of agar plate culture whereas other signatures such as changes in the protein profile are indirect evidence of different culture conditions but not of any one condition or recipe in particular. The residual metal content of the sample can also provide indication of the culture environment of bacteria and when tied to other indirect evidence provide more confidence in information about the culture environment.