Sk. Lower et al., Bacterial recognition of mineral surfaces: Nanoscale interactions between Shewanella and alpha-FeOOH, SCIENCE, 292(5520), 2001, pp. 1360-1363
Force microscopy has been used to quantitatively measure the infinitesimal
forces that characterize interactions between Shewanella oneidensis (a diss
imilatory metal-reducing bacterium) and goethite (alpha -FeOOH), both commo
nly found in Earth near-surface environments. Force measurements with subna
no-newton resolution were made in real time with living cells under aerobic
and anaerobic solutions as a function of the distance, in nanometers, betw
een a cell and the mineral surface. Energy values [in attojoules (10(-18) j
oules)] derived from these measurements show that the affinity between S. o
neidensis and goethite rapidly increases by two to five times under anaerob
ic conditions in which electron transfer from bacterium to mineral is expec
ted. Specific signatures in the force curves suggest that a 150-kilodalton
putative iron reductase is mobilized within the outer membrane of S. oneide
nsis and specifically interacts with the goethite surface to facilitate the
electron transfer process.