In research published today in Science, the scientists used high-energy X-ray fluorescence measurements for mapping and chemical analyses of single free-floating, or planktonic, and surface-adhered, or biofilm, cells of Pseudomonas fluorescens. The results showed differences between the planktonic and adhered cells in morphology, elemental composition and sensitivity to hexavalent chromium, a heavy-metal contaminant and a known carcinogen. The biofilm cells were more tolerant of the contaminant, while it damaged or killed the planktonic cells.
In addition to determining the chemical differences between the cells, the work also pioneers a potentially revolutionary new technique for investigating microbiological systems in natural subsurface environments. This study advanced the development of high-energy X-ray microprobes and methods for using the microprobes to investigate single bacterial cells. The new capabilities set the stage for future studies defining mineral-metal-microbe interactions in contaminated environments.
"This technique also should be directly applicable to investigations of microbial processes in extreme subsurface environments and to studies of a variety of astrobiology topics, such as detection of past or present life in samples returned from Mars, or determinations of the origins of life," said lead author Ken Kemner of Argonne's Environmental Research Division.
No previously available techniques had the spatial resolution needed to analyze individual bacterial cells noninvasively and nondestructively. Recent developments at the Advanced Photon Source (APS) at Argonne enabled the production of X-ray beams small enough to probe single bacterial cells, which are typically one-hundredth the diameter of a human hair. The APS provides the nation's mo
Contact: Donna Jones Pelkie
DOE/Argonne National Laboratory