APPLICATION OF ATOMIC-FORCE MICROSCOPY TO STUDIES OF MICROBIAL INTERACTIONS WITH HYDROUS FE(III)-OXIDES

We are using atomic-force microscopy (AFM), to address the interaction s of a Pseudomonas sp. aerobic soil microbe with Fe(III)-(hydr)oxides. Research results to date show that AFM is a viable technique for in-s itu and ex-situ imaging of bacteria attached to mineral surfaces. Deli cate microbial structures and mineral surface microtopographies are re adily accessible. However, sample preparation has proven to be crucial . For example, we found that an organic extractant used to separate ba cteria from particle surfaces left a residue that could be mistaken fo r dissolution features in AFM images. Additionally, care must be taken to image samples in numerous locations and under a wide variety of co nditions. The need for extensive imaging was reinforced by our observa tions that most reacted particles had no obvious dissolution features, but a small fraction of particles were extensively eroded. Hence, mic robe-Fe(III)-(hydr)oxide interactions lead to enhanced dissolution, bu t the dissolution process is heterogeneous in nature. Thus, although A FM imaging of such complex systems is difficult and time-consuming, a painstaking approach is needed.