Figure 1. Examples of services provided by microorganisms. Clockwise from top: microorganisms in the sea remove carbon dioxide from the atmosphere and produce oxygen; the ozone layer in the stratosphere, which protects Earth from harmful ultraviolet rays, was created by the reaction of oxygen molecules produced on the early Earth by microbes; the human body contains more bacterial cells than human cells and most of these live in the gastrointestinal tract; certain bacteria convert dinitrogen gas to ammonia in special structures on the roots of leguminous plants; soil bacteria are the source of most of the antibiotics and many other drugs used in medicine today; microbes ferment many foods; centre, microorganisms come in many shapes and sizes. Graphic: Nicolle Rager Fuller.

Figure 2. Construction and analysis of metagenomic libraries. Graphic: Nicolle Rager Fuller.

Figure 3. (a) Tube worms containing bacterial symbionts. Courtesy: National Science Foundation (Courtesy: National Science Foundation). (b) Bacterial symbionts inside the tube worm (Courtesy of Colleen M Cavanaugh). See also

Figure 4. DNA cloned from soil confers many traits on E. coli. (a) Left plate contains no antibiotics, right plate contains -lactam antibiotic. Clone ‘C’ carries a gene from the soil metagenome that makes E. coli resistant to the -lactam antibiotic. (b) Clone on left contains no heterologous DNA. The other four clones carry DNA fragments from soil metagenomic that confer on E. coli the ability to produce pigments. Photos: Heather Allen and Lynn Williamson.