BACTERIA: SIMPLE IN STRUCTURE AND SIMULTANEOUSLY ESSENTIAL AND HAZARDOUS TO ENVIRONMENTAL HEALTH
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FIGURE 11.6 The simple physical structure shown here belies the metabolic complexity of bacteria. Nitrogen-fixing bacteria are essential to the functioning of all ecosystems. Yersinia pestis, the bacterial species that was the source of the Black Plague, is still a hazard in many parts of the world.
(Hugh Spencer/Science Source/Colorization by Mary Martin) (National Institute of Allergy and Infectious Diseases (NIAID))