Microbes Flashcards
Name four categories of microbes.
Bacteria, viruses, prions, and other organisms (such as fungi, multicellular parasites, and single-celled protistans.
Microbes
Microbes are microscopic organisms and particles.
Pathogens
Microbes that cause disease in humans
Give three positive uses of microbes.
Microbes can be used to make many foods, drugs, and they are important as decomposers to recycle nutrients.
Describe bacteria.
Bacteria are single-celled, prokaryotic organisms. Almost all have a cell wall, and have DNA in a single chromosome - no nucleus. Some have plasmids. They have ribosomes, and reproduce by binary fission.
Plasmids
Accessory rings of DNA in bacterium
What does reproduction by binary fission result in?
Reproduction by binary fission results in 2 cells that are identical to the original cell.
What can be used to combat pathogenic bacteria?
Antibiotics can interfere with reproduction and survival of bacteria.
Name the three shapes of bacteria, and the words that describe the shape.
Sphere-shaped - “coccus”
Rod-shaped - “bacillus”
Curve-shaped - “spirillum”
Describe viruses.
Viruses are small, nonliving obligate parasites. They are acellular (not composed of cells). They all have an outer protein coat called a capsid and nucleic acid (RNA or DNA) inside. Some also have an envelope.
Why are viruses considered nonliving?
Viruses are considered nonliving because they cannot reproduce by themselves, and must reproduce inside of a host cell.
Capsid
The outer protein coat on a virus
Do antibiotics work against viruses?
No, because antibiotics affect the reproduction of their target, and viruses don’t reproduce on their own - they hijack host cells, which we don’t want to target.
What does the damage from a virus depend on?
The damage from a virus depends on the efficiency of the immune system and the ability of the infected tissue to repair itself (e.g. common cold - respiratory track - versus polio - nerve cells)
Prions
Infectious protein particles. They occur when normal proteins change shape.
What do prions cause?
Prions cause degenerative disease of the nervous system, calcified plaque.
Epidemiology
The study of diseases in populations
Infectious Diseases
Diseases caused by pathogenic microbes, including bacteria, viruses, prions, fungi, parasites, and protozoans
Epidemic
More cases of the disease than expected in a certain area for a certain period.
Outbreak
If the epidemic is confined to a local area
Pandemic
A global epidemic
What genes comprise the H1N1 influenza virus?
Two genes from pig flu viruses, one from avian flu viruses, and one from human flu viruses
When was the first human to human transmission of H1N1 recorded in the US?
April 2009
Phases 1-3 of a pandemic
Predominantly animal infection. Relatively few human infections.
Phase 4
Sustained human to human transmission.
Phases 5-6
The pandemic stage, in which there is widespread human infection.
Post Peak stage of Pandemics
There is a possibility of recurring events, but the worst is over.
Post Pandemic stages
The disease is at expected seasonal outbreak levels.
Roughly how many people in the US die of the flu and flu related complications?
About 36,000 people each years - predominantly elderly and very young.
HIV
Human Immunodeficiency Virus, which kills white blood cells essential to immune system function and results in low CD4 count and secondary infections.
AIDS
Acquired ImmunoDeficiency Syndrome, in which there is a low CD4 count, and a collection of infections and malignancies builds up, which eventually kill the infected individual.
Category A Phase of HIV infection
Asymptomatic, but highly infectious
CD4 count is above 500 cells/mm^3
Category B Phase of HIV infection
Has one or more of a variety of symptoms related to an impaired immune system, and a CD4 count between 200-499 cells/mm^3.
Category C Phase of HIV infection
At this point, the person has AIDS, in which they have one or more of the AIDS opportunistic infections that is eventually the cause of death. CD4 count has fallen below 200 cells/mm^3.
Where and when did HIV originate?
HIV originated in Africa in the late 1950’s or earlier. It is thought to originate from non-human primates, possibly among bushmeat handlers.
When was the first documented case of HIV in the US?
1969.
When was HIV found to be the cause of AIDS?
1983-1984
Roughly how many people are living with HIV?
About 33.2 million people are living with HIV.
Where do most people living with HIV live?
Most people living with HIV live in developing countries.
How is HIV transmitted?
HIV is transmitted through sexual contact, dirty needles, a blood transfusion, or to a baby from their mother. Heterosexual sex is the most common mode of transmission. It is not passed through casual contact.
How can one prevent HIV?
Abstinence, sex with only one uninfected partner, and proper, consistent use of condoms.
What does the HIV test test for?
The HIV test searches for HIV antibodies, not the virus itself.
How long does it take for antibodies to HIV to develop and thus show up on a test?
Most people develop antibodies to HIV within 2-8 weeks of infection, but it can take 3-6 months.
How does drug therapy for HIV work?
Highly active antiretroviral therapy uses a combination of drugs to inhibit HIV replication.
Endotoxins
Chemical components of outer bacterial cell walls
Exotoxins
Poisonous proteins secreted by bacterial cells
How do pathogenic bacteria affect one’s system?
Pathogenic bacteria affect one’s system by producing poisons.
Lyme Disease
A bacterial disease, endotoxin, carried by “deer” ticks that can be found on the white-footed deer mouse and white-tailed deer.
What are the symptoms of Lyme disease?
Early - bull’s eye rash, fever, headache, fatigue, depression, flu-like symptoms, muscle-aches
Late - arthritis, heart disease, nervous system impairment, rarely death
