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Until the second half of the 19th century it was thought that life could arise spontaneously from nonliving matter, a process known as spontaneous generation. Francesco Redi was an early opponent of this theory and demonstrated in 1668 that maggots, fly larvae, do not arise spontaneously from meat. Many people still believed in the theory. In 1745, John Needham poured heated nutrient fluids into covered flasks and found the presence of microorganisms. He took this as evidence of spontaneous generation. Twenty years later Lazzaro Spallanzani showed that Needham's microorganisms entered the flasks after boiling. In 1861, Louis Pasteur designed the experiments that finally ended this long debate. He showed that flasks left open to the air after boiling would soon be contaminated but if they were sealed, they remained free of microorganisms. He also used flasks with s-shaped curves. Air could enter the flasks however the microorganisms could not and the contents of the flask remained sterile. This proved that microorganisms are present throughout the environment but can be destroyed. He also developed methods of blocking access of airborne microorganisms to nutrient environments, these methods were the basis of aseptic technique. Pasteur pipets are named after Louis Pasteur and are used in laboratories around the world.

The easiest way to make a slide of bacteria is to prepare a wet mount similar to what is used for algae and protozoa. The problem with bacteria is that they are small and colorless. Beginning microbiologists have trouble finding the microorganisms under the microscope. The most effective way for a beginning microbiologist to view bacteria is to use a method known as background or negative staining. This process involves mixing the bacteria in a small drop of nigrosine and spreading the drop over a slide. Nigrosine has an overall negative charge as does the bacterial cell wall therefore the stain is repelled from the bacterium. No heat is applied to the slide so the mophology of the cell is not affected. The species spirochaetes is harder to stain which makes negative staining more suitable. It is very important to keep laboratory safety in mind when working with microorganisms.

Recombinant DNA is DNA that is created from two or more sources to form a recombinant DNA molecule. Recombinant DNA is formed by introducing DNA of interest into DNA that already exists in an organism, such as the plasmid of a bacterium. This recombinant DNA codes for or alter traits for a specific purpose such as antibiotic resistance. Recombinant DNA is not a natural process, it is engineered. Biosynthetic insulin was the first medicine to be made by way of recombinant DNA technology. Insulin is a relatively simple protein and was easy to copy. The specific gene sequence was introduced into E. coli., the bacteria found in the human intestine. Biosynthetic insulin did not spike in popularity until manufacturers removed highly purified animal insulin from the market leaving no alternative. North Safety, Drummond, and Kendall all provide products used in recombinant DNA technology research.

Each year industrial plants generate 265 million metric tons of hazardous waste, 80% of which make their way into landfills. Burying the chemicals does not remove them from the ecosystem, however it just moves them into other areas where they can find their way into bodies of water. Traditional chemical analyses to locate these chemicals are expensive and can't distinguish chemicals that affect biological systems from those that lie inert in the environment. In response to this problem, scientists are devloping biosensors, bacteria that can locate biologically active pollutants. These biosensors do require expensive chemicals or equipment and they work quickly. Bacertial biosensors require a receptor that is activated in the presence of pollutants and a reporter that will make this change apparent. For example, a bacterium that contains the lux operon will emit visible light when the receptor is activated by a specific pollutant. Yeast containing genes encoding mammalian odor receptors and GFP (green fluorescent protein) will fluoresce in the presence of TNT. Beckman Coulter, Motic, and Pall supply products used in biosensor research.