Bacteria Beneficial and Harmful Bacteria break down large biological molecules into more simple ones that can be used by plants. This is decay and can be harmful if what is being broken down is food or something that we do not want to see decayed. Some bacteria can change substances into more useful forms. Example: Nitrogen fixing bacteria that live in the roots of certain plants called legumes (beans and peas). Bacteria can be used to make vinegar (acetic acid fermentation) This is important is producing sauerkraut, yogurt and sourdough bread. Some types of cloth need bacteria to help in their processing like linen and leather. Buttermilk and most cheeses are made with bacteria (some cheeses are made with molds) Bacteria are used to make chemicals that fight other bacteria (antibiotics) Some bacteria are used to kill insects (bacillus thurigensis) BT This cases a disease in caterpillars that harm many important food plants. Scientists have isolated the gene that the bacteria use to produce a poison that kills the insect larvae and inserted it into the plant itself. Now the plant is poisonous to the insects. BT corn and Bt soybeans are banned in Europe. They reduce butterfly populations. Harmful effects and how we fight them. Food Spoilage - the bad side of decay bacteria Prevention: • Heating - kills bacteria • Drying - no extra water to support bacteria. This is why dried fruit and meat lasts so long. • Salting - Kills many bacteria. They have trouble with osmosis (remember that?) • Smoking - keeps bacteria from growing. Many chemicals that are in wood smoke kill bacteria. This is why ham was invented. • Cooling - this greatly slows down bacteria reproduction rates. Why we have refrigerators. •Pasteurization - controlled heating to destroy bacteria. usually used in milk products Bacteria cause direct harm to animals and plants by actively living in them and casing disease or by producing chemicals that are harmful. Humans - many diseases. Strep throat, skin infections are examples are examples of bacteria living on or in us. Some bacteria produce toxins that are very dangerous. Clostridium botulinum and Clostridium tetani are examples. Animal diseases - Anthrax and cholera are examples. Plant diseases - Blights and rots.