Bacteria-clay interaction: Structural changes in smectite induced during biofilm formation

Abstract

Bacteria play an important role in determining the properties and behavior of clay minerals in natural environments and such interactions have great potential for creating stable biofilms and carbon storage sites in soils, but our knowledge of these interactions are far from complete. The purpose of this study was to understand better the effects of bacteria-generated biofilms on clay interlayer expansion. Mixtures of a colloidal, 2-water hectorite clay and Pseudomonas syringae in a minimal media suspension evolve into a polysaccharide-rich biofilm aggregate in time-series experiments lasting up to 1 week. X-ray diffraction analysis reveals that upon aggregation, the clay undergoes an initial interlayer contraction. Short-duration experiments, up to 72 h, result in a decrease in the d001 value from 1.50 to 1.26 nm. The initial interlayer contraction is followed in long-duration (up to 1 week) experiments by an expansion of the d001 value of 1.84 nm. The expansion is probably a result of large, biofilm-produced, polymeric molecules being emplaced in the interlayer site. The resultant organo-clay could provide a possible storage medium for carbon in a microbial colony setting.

Microbial communities in bentonite formations and their interactions with uranium

“…are reported to produce extracellular polymers (mainly polysaccharides but also proteins and nucleic acids), which facilitate the cells to adhere to mineral surface and to solubilize Fe(III) needed for the cell growth. Mixtures of hectorite clay and Pseudomonas syringae in a minimal media suspension evolve into a polysaccharide-rich biofilm aggregate (Alimova et al, 2009). Representatives of Sphingomonas have also been identified as major populations in biofilms formed in naturally nickel-polluted river water (Lawrence et al, 2004).…”

Rapid microbial stabilization of unconsolidated sediment against wind erosion and dust generation

“…This indicates that smectite underwent a process of dehydration (loss of water from the interlayer space results in peak displacement) that affected the smectite layers in different extent (widening of the peak). Such effect has been observed in smectite-bacterial interaction, although only as an intermediate stage lasting 3 h to 3 days, followed by a state in which the first smectite peak moved to ∼18 Å (Alimova et al 2009). They interpreted the transient stage with the smectite peak at 12.6 Å as partial dehydration caused by the penetration of small organic molecules in the smectite interlayer, which created a more hydrophobic environment.…”

Organic matter sequestered in potential energy fields predicted by 3-D clay microstructure model

“…The 3-D imaging techniques can be extended to develop a far more comprehensive understanding of the geometrical structure of soils and sediments including morphology and dimensional analysis of (1) the pore space and pathways, (2) domains and aggregates, (3) fabric and signatures, and (4) OM distribution. The 3-D techniques may be applicable to investigation of sequestration of OM between clay mineral layers, such as reported in the presence of Pseudomonas syringae polysaccharides by Alimova et al (2009). Other important areas of research that our modeling and 3-D imaging may advance include investigations of particle size and reactivity and molecular dynamics near nanoscaleparticle surfaces (Arnarson and Keil, 2001), the nucleation of ice crystals in clouds (Pratt et al, 2009), the medical applications of clays (Wayman, 2008), and the peculiar behavior of nanoscale particles within biological systems, with particular focus on potential toxic effects (Nel et al, 2006).…”