how bacteria affects human lives

immune system
1. secondary response
  1. if a bacteria re-eneters the body, clonal selection happens a lot faster
    1. memory B-cells are activated and divide into plasma cells that produce the right antibody to the antigen on the bacteria
    2. memory T-cells are activated and divide into the correct type of T-cells to kill the carrying antigen
    3. the pathogen is often gone before you show any symptoms as you are immune to that specific bacteria
2. primary response
  1. phagocytes engulf the pathogen and break it down using lysozymes and then the antigens are presented on the phagocytes surface to activate other immune system cells
    1. phagocytes activate cytotoxic T-cells to kill pathogens and activate helper T-cells to secrete the correct antibodies
      1. clonal selection occurs where T-cells activate B-cells which divide into plasma cells
        plasma cells make monoclonal antibodies to the specific antigen of the bacteria
3. immunity
  1. vaccines
antibiotic resistance
1. some bacteria have a random mutation that gives them a resistance to antibiotics
  1. the population is exposed to the antibiotic, killing bacteria without the resistant allele
    1. the resistant bacteria survive and reproduce without competition, passing on the allele that gives antibiotic resistance to their offspring
      1. after some time, most organisms in the population will carry the antibiotic resistance allele and there will be a new strain of bacteria
2. MRSA
nitrogen cycle
1. nitrogen fixation
  1. free-living nitrogen-fixing bacteria
    1. reduce gaseous nitrogen to ammonia which they then use to manufacture amino acids
    2. nitrogen-rich compounds are released from them when they die and decay
  2. mutualistic nitrogen-fixing bacteria
    1. live in nodules on the roots of leguminous plants
    2. they obtain carbohydrates from the plant and the plant acquires amino acids from the bacteria
2. denitrification
  1. nitrates in the soil are converted into nitrogen gas by denitrifying bacteria
  2. they use nitrates in the soil to carry out respiration and produce nitrogen gas
3. nitrification
  1. ammonium ions in the soil are changed into nitrogen compounds
    1. these can then be used by plants (nitrates)
    2. nitrifying bacteria change ammonium ions into nitrites
      1. more nitrifying bacteria turn nitrites into nitrates
4. ammonification
  1. nitrogen compounds from dead organisms and animal waste are turned into ammonia by saprobionts
5. plants, animals and humans need nitrogen to make amino acids, proteins and nucleic acids
  1. atmosphere is 78% nitrogen but plants, animals and humans cant use it in that form
    1. bacteria convert it into nitrogen containing compounds first
      1. this way plants can use the nitrogen, meaning it can make its way into the food chain and to humans

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how bacteria affects human lives

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