E. Identification of bacterial types by Gram Staining

1. Gram Positive; stain applied to the bacterium will 1. Gram Positive; stain applied to the bacterium will color the cell purple. a. beneficial- *actinomycetes used as antibiotics (tetracycline and streptomycin) kill other bacteria by preventing them from making proteins. * used in the food industry of making pickles, yogurt, and buttermilk b. harmful- many produce toxins * Clostridium botulinum (botulism) causing food poison. A single gram of the toxin could kill more than a million people.

2. Gram Negative; stain colors cell pink a. beneficial- * Escherichia coli (E. coli)- lives in intestines of humans where it produces vitamin K and helps break down food. b. harmful- many disease causing because of toxins. * Salmonella sp.- responsible for food poisoning.

F. Reproduction; 1. asexual- binary fission; Small circular chromosome and smaller circular pieces of DNA (plasmids) keep cells from dividing by mitosis or meiosis. Chromosomes are copied, then move to opposite ends of the bacterium. Bacterium grows larger, then splits into two bacteria. Some bacteria can reproduce every twenty minutes. 2. sexual- conjugation; bacteria will connect by a structure called a pilus (plural, pili). Chromosome or chromosome fragments are transferred from one bacterium to another.

Once chromosomes are transferred, binary fission Once chromosomes are transferred, binary fission occurs to create new bacterium. G. Endospore formation; Temperatures of 100°C usually kill bacteria. Endospores are a protective structure, which is created by the bacterium, to keep the cell from drying out and protect its DNA. Bacteria can’t reproduce when they are in an endospore stage. When conditions improve, the bacteria come out of the endospore stage and begin to reproduce again.

III. Antibiotics; usually disrupt the bacteria’s ability to build a cell wall and/ or keeps the bacteria from reproducing. Antibiotic resistance can occur in bacteria when antibiotics are not used appropriately. A bacterium that is resistant to antibiotics because of a genetic mutation can quickly and easily spread that resistance through conjugation.