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In this review, we describe four approaches to the materials synthesis of organized inorganic matter. These include the use of self-assembled organic templates (transcriptive synthesis), cooperative assemblies of templates and building blocks (synergistic synthesis), spatially restricted reaction fields (morphosynthesis), and combinations of these approaches (integrative synthesis) in the area of sol-gel chemistry. We illustrate these strategies, respectively, by describing recent work on the formation of silica-based organized materials, viz. the preparation of ordered silica macrostructures using bacterial templates, templatedirected synthesis of ordered hybrid mesophases and organoclays, synthesis of microskeletal frameworks of silica and other metal oxides in compartmentalized liquids, and use of bacterial superstructures in the fabrication of hierarchical macrostructures of mesoscopically ordered silica.

The swimming motions of cells within Bacillus subtiliscolonies, as well as the associated fluid flows, were analyzed from video films produced during colony growth and expansion on wet agar surfaces. Individual cells in very wet dense populations moved at rates between 76 and 116 μm/s. Swimming cells were organized into patterns of whirls, each approximately 1,000 μm2, and jets of about 95 by 12 μm. Whirls and jets were short-lived, lasting only about 0.25 s. Patterns within given areas constantly repeated with a periodicity of approximately 1 s. Whirls of a given direction became disorganized and then re-formed, usually into whirls moving in the opposite direction. Pattern elements were also organized with respect to one another in the colony. Neighboring whirls usually turned in opposite directions. This correlation decreased as a function of distance between whirls. Fluid flows associated with whirls and jets were measured by observing the movement of marker latex spheres added to colonies. The average velocity of markers traveling in whirls was 19 μm/s, whereas those traveling in jets moved at 27 μm/s. The paths followed by markers were aligned with the direction of cell motion, suggesting that cells create flows moving with them into whirls and along jets. When colonies became dry, swimming motions ceased except in regions close to the periphery and in isolated islands where cells traveled in slow whirls at about 4 μm/s. The addition of water resulted in immediate though transient rapid swimming (> 80 μm/s) in characteristic whirl and jet patterns. The rate of swimming decreased to 13 μm/s within 2 min, however, as the water diffused into the agar. Organized swimming patterns were nevertheless preserved throughout this period. These findings show that cell swimming in colonies is highly organized.

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