CARBONATE MINERALS AND BIOFILM FORMATION: CHEMISTRY, CRYSTAL STRUCTURE AND REDOX FACTORS

We are engaged in a study of the chemical and physical factors that affect the ability of a model organism (Shewanella oneidensis (MR-1)) to recognize discrete sites on the crystal surface, attach to them and propagate a biofilm. We have already demonstrated that MR-1 can completely control the dissolution kinetics of calcite at neutral pH (Conrad and Luttge, 2001, Luttge and Conrad, 2002) and in other abstracts submitted to this meeting, we report on its behavior in natural seawater and on a dolomite substrate. We have selected our model organism because of its frequent occurrence at chemical interfaces in natural environments, and because of its ability to thrive both in aerobic and in anaerobic conditions.

We have learned that MR-1 can distinguish the difference between surfaces of carbonates populated with cations other than Ca, as demonstrated by changes in its behavior with respect to surface attachment and biofilm propagation on cleavage (charge-neutral) surfaces of various carbonates in the calcite, dolomite and aragonite groups. Because MR-1 is known to reduce both Fe and Mn, the attachment behavior of MR-1 on both siderite and rhodochrosite is of particular interest.

Here we explore the recognition, attachment and biofilm propagation behavior of MR-1 in a systematic manner with respect to crystal chemistry and structure as well as with respect to metabolic state (aerobic vs anaerobic).