Importance of Bacteria to Humans Additional ways prokaryotes are important to us 1) We use prokaryotes to produce food! 2) Mutualistic endosymbiotic prokaryotes help us digest food and produce certain vitamins! Breyers Light Probiotics Plus Yogurt contains an added dose of live, active Bifidobacterium yogurt culture. 3) We use prokaryotes to mine certain minerals! 4) We use prokaryotes to purify water! 5) We use prokaryotes in genetic engineering to produce human proteins for medication! 20
Prokaryotic Diversity 19-3 Diseases Caused by Bacteria and Viruses Bacterial pathogens Of the 20 bacterial phyla currently recognized, thirteen are not present in this figure due to the absence of noteworthy pathogens. Some of these missing phyla are relatively important, like the Cyanobacteria. This type of diagram is a phylogenetic tree and shows evolutionary relationships between classification groups and/or species. Generally, bacteria and viruses can be found throughout the biosphere! However, reletively few actually cause disease. A pathogen is a disease-causing entity. They cause disease by killing cells or interfering with normal metabolic function... 21
Bacterial Diseases Bacterial pathogens produce these symptoms: 1) Locally, by producing cell/tissue damage at the site of infection. 2) Systemically (body-wide), by producing/releasing compounds (toxins) that interfere with metabolism. Exotoxins are components of bacterial pathogens released upon their lysis (death). Endotoxins are compounds released by living pathogens as metabolic waste. 22
Bacterial Disease in Humans As for viral pathogens, there are vaccines to protect against prokaryotic pathogens as well. A vaccine is a substance (piece of pathogen) used to stimulate the immune system to produce antibodies and remember the pathogen, providing immunity. Immunity is the ability to resist a particular pathogen or toxin by the action of the immune system. The two components of the immune system are: 1) Innate Prevents initial infection (skin, nose hairs, mucus, enzymes, macrophages, killer T-cells). 2) Adaptive or Acquired - Learns and remembers how to fight off specific pathogens (macrophages, dendritic cells, helper T-cells, B-cells, antibodies). A vaccine is made from an antigen isolated or produced from the disease-causing microorganism. The vaccine is injected into the blood stream. Macrophages patrolling tissues recruit Killer T-cells which go to work to remove the threat. B-cells in the blood stream, with the help of helper T-cells, respond to the antigen by producing antibodies. The antibodies bind to the antigen to "neutralize"or inactivate it. In addition, memory cells are produced and remain ready to mount a quick protective immune response against subsequent infection with the same disease causing agent. 23
Determining Antibiotic Sensitivity Effects of different antibiotics on growth of a Bacillus strain. The right-hand image shows a close-up of the novobiocin disk (marked by an arrow on the whole plate). In this case some individual mutant cells in the bacterial population were resistant to the antibiotic and have given rise to small colonies within the zone of inhibition. An antibiotic is a medication used to kill prokaryotic or other living pathogens. The disk with no zone of inhibition is the control? It likely has only distilled water. Antibiotic resistance refers to the capacity of pathogens to not be killed by antibiotics. Bacteria may become resistant through mutation or horizontal gene transfer. Antibiotic sensitivity is the degree to which a pathogen can be killed by an antibiotic. The zone of inhibition is the area around the disk where bacterial growth is inhibited. A bacterial population is most likely to be sensitive to an antibiotic during reproduction. Based on these results, the antibiotics that should be most effective are the ones with the widest, clearest zone of inhibition. 24
Controlling Bacteria Autoclave (heat & pressure) A hamburger patty cooked to 160 F, regardless of color, is safe. Prokaryotes can be controlled by: 1) Refrigeration Prevents prokaryotic reproduction by slowing their metabolism. 2) Disinfection Lysol is called Lysol because it results in prokaryotic cell lysis! 3) Thorough cooking Heat kills most pathogenic prokaryotes. 4) Sterilization Heat and pressure kills most pathogenic prokaryotes (pressure cooker, autoclave). 25