Hydrodynamic Interactions, Hidden Order, and Emergent Collective Behavior in an Active Bacterial Suspension.

Spontaneous self-organization (clustering) in magnetically oriented bacteria arises from attractive pairwise hydrodynamics, which are directly determined through experiment and corroborated by a simple analytical model. Lossless compression algorithms are used to identify the onset of many-body self-organization as a function of experimental tuning parameters. Cluster growth is governed by the interplay between hydrodynamic attraction and magnetic dipole repulsion, leading to logarithmic time dependence of the cluster size. The dynamics of these complex, far-from-equilibrium structures are relevant to broader phenomena in condensed matter, statistical mechanics, and biology.

Tuning bacterial hydrodynamics with magnetic fields.

Magnetotactic bacteria are a group of motile prokaryotes that synthesize chains of lipid-bound, magnetic nanoparticles called magnetosomes. This study exploits their innate magnetism to investigate previously unexplored facets of bacterial hydrodynamics at surfaces. Through use of weak, uniform, external magnetic fields and local, micromagnetic surface patterns, the relative strength of hydrodynamic, magnetic, and flagellar force components is tuned through magnetic control of the bacteria's orientation. The resulting swimming behaviors provide a means to experimentally determine hydrodynamic parameters and offer a high degree of control over large numbers of living microscopic entities. The implications of this controlled motion for studies of bacterial motility near surfaces and for micro- and nanotechnology are discussed.

The pedagogical genealogy of Terrance J. Beveridge--a legacy of bonds.

Terrance J. Beveridge (TJB) was a professor at the University of Guelph for nearly three decades. He died on September 10, 2007. TJB was a pioneer who pushed the frontier of microbiology and bacteriology. His legacy includes 22 postdoctoral scholars and 24 graduate students. His two dozen graduate student progeny have, in turn, mentored at least 52 additional graduate students. This paper presents TJB's pedagogical tree and touches on many of the topics that he studied during his life including: bacteria cell surfaces, biomineralization, biofilms, and geomicrobiology.

Bacterial recognition of mineral surfaces: nanoscale interactions between Shewanella and alpha-FeOOH.

Force microscopy has been used to quantitatively measure the infinitesimal forces that characterize interactions between Shewanella oneidensis (a dissimilatory metal-reducing bacterium) and goethite (alpha-FeOOH), both commonly found in Earth near-surface environments. Force measurements with subnanonewton resolution were made in real time with living cells under aerobic and anaerobic solutions as a function of the distance, in nanometers, between a cell and the mineral surface. Energy values [in attojoules (10(-18) joules)] derived from these measurements show that the affinity between S. oneidensis and goethite rapidly increases by two to five times under anaerobic conditions in which electron transfer from bacterium to mineral is expected. Specific signatures in the force curves suggest that a 150-kilodalton putative iron reductase is mobilized within the outer membrane of S. oneidensis and specifically interacts with the goethite surface to facilitate the electron transfer process.