Matthew Tyska, Ph.D., recalls being intrigued, from the first day of his postdoctoral fellowship in 1999, with a nearly 30-year-old photograph. It was an electron micrograph that showed the internal structures of an intestinal cell microvillus, a finger-like protrusion on the cell surface. Microvilli are common features on the epithelial cells that line the body's cavities.

In genetic engineering's version of the Pied Piper, chemists have programmed E. coli bacteria to move toward new chemical signals - an advance they say could enable the production of bacteria with important uses in medicine, environmental clean-ups, and other fields.

Drs. Michael Sieracki and Ramunas Stepanauskas, scientists at Bigelow Laboratory, have proven a new approach of obtaining genetic codes of ocean microbes, based on the analysis of individual unicellular organisms.

The emerging field of metagenomics, where the DNA of entire communities of microbes is studied simultaneously, presents the greatest opportunity -- perhaps since the invention of the microscope -- to revolutionize understanding of the microbial world, says a new report from the National Research Council.

Until a decade ago, scientists categorized microorganisms almost exclusively by their physical characteristics: how they looked, what they ate, and the by-products they produced. With the advent of genomic sequencing and genetic analysis in the 1990s, our understanding of the relationships between different microorganisms fundamentally changed. In light of this new knowledge, what exactly is the definition of a microbial species, and how should microbiologists be categorizing microorganisms?