A New Perspective on Bacteria

is carried on a DNA loop in the cytoplasm with the membrane possessing some nuclear properties. There are three main kinds of bacteria – spherical, rod-like, and spiral – known by their Latin names of coccus, bacillus, and spirillum. Bacteria occur alone, in pairs, clusters, chains, or more complex configurations. Some live where oxygen is present; others, where it is absent. The relationship between bacteria and their hosts is symbiotic, benefitting both organisms, or the hosts may be destroyed by parasitic or disease-causing bacteria. B In general, humans view bacteria suspiciously, yet it is now thought they partly owe their existence to microbes living long, long ago. During photosynthesis, plants produce oxygen that humans need to fuel blood cells. Most geologists believe the early atmosphere on Earth contained very little oxygen until around 2½ billion years ago when microbes bloomed. Ancestral forms of cyanobacteria, for example, evolved into chloroplasts – the cells that carry out photosynthesis. Once plants inhabited the oceans, oxygen levels rose dramatically, so complex life forms could eventually be sustained. The air humans breathe today is oxygen-rich, and the majority of airborne microbes are harmless, but…