Microorganisms Flashcards
Define “disease”
A condition with a specific cause in which part or all of the body functions abnormally
How do microorganisms cause diseases?
Bacteria: Release toxins when they multiply which affect cells in the region of infection
Virus: Affect the metabolic systems of the cell. The genetic material of the virus takes over the cell and instructs it to produce more viruses
Fungi: Hyphae secrete digestive enzymes that break down the tissues; can physically damage tissues/cause an allergic reaction
Protozoa: No set pattern
Three basic shapes of bacteria:
Spirals, rods, and spheres
The process by which bacteria reproduce:
Binary fission
Where can bacteria be cultured?
Agar jelly or broth
Stages of the bacterial growth curve
LAG PHASE: adjusting to the new environment
GROWTH PHASE: division of bacteria
STATIONARY PHASE: rate of growth of new cells equals the rate of death of cells
DEATH PHASE: more and more cells die
What limiting factors cause the stationary and death phase?
The build-up of toxins/ poisonous waste products
Using up nutrients and oxygen
What’s a parasite?
An organism that lives in or on another organism, called its host and causes it harm
The course of a disease:
Infection period ➡ Incubation period ➡ Symptoms
Means of infection:
- Droplets (respiratory diseases)
- Drinking contaminated water (colonize in regions of the gut)
- Eating contaminated food (regions of the gut)
- Direct contact (skin infection or other diseases)
- Sexual intercourse (STDs)
- Blood-to-blood contact (STDs)
- Animal vectors
Define “syndrome”
A set of symptoms caused by a medical condition
Role of T-helper cells:
To help other lymphocytes to become active and start fighting infections
A typical infection with HIV involves this course:
- The virus makes DNA from the RNA. It gets incorporated into the DNA of the T-helper cell.
- At some point the HIV DNA gets activated and instructs the T-helper to make HIV proteins and more RNA.
- The HIV proteins and the RNA are assembled into new virus particles.
- Some of the HIV proteins end up as antigens on the surface of the lymphocyte which are recognized by the immune system as foreign and so the lymphocyte is destroyed by the immune system.
- The assembled virus particles escape into other lymphocytes. The cycle repeats for as long as the body can replace the lymphocytes that have been destroyed. Eventually, the body will not be able to do so.
- The number of viruses in the blood increases and HIV may infect other areas of the body. The immune system is severely damaged, and other pathogens infect the body. The person usually dies due to opportunistic infections
What is the latency period?
The period during which the body can replace the lymphocytes as quickly as they are being destroyed. Shows no symptoms at the time
The main ways HIV is transmitted are:
Unprotected sexual intercourse
Blood to blood contact (infected needles)
How can the transmission of HIV be reduced?
Using condoms
Using new, sterile needles
Limiting the no. of sexual partners
Testing the blood used for transfusions
The incubation period for the Ebola virus:
2 to 21 days (not infectious)
Symptoms of Ebola:
Fever Muscle pain Headache Sore throat Vomiting Diarrhea Rash Damaged liver and kidney Internal and external bleeding Low WBC and platelet count
How can direct contact cause Ebola?
Through broken skin and mucus membranes (mouth and intestine)
Through infected surfaces eg. bedding
Prevention and control methods for Ebola:
- Reduce the risk of transmission from animals (eg. thoroughly cooking meat)
- Reduce the risk of transmission from infected people (eg. wearing gloves, protective clothing, washing hands)
- Reduce the risk of transmission from sexual intercourse
- Containing the outbreak (isolating people, monitoring patient contacts, having testing facilities, safe burial)
Treatment for the symptoms of the Ebola disease:
ORH: a solution of salts and glucose dissolved in sterile water
The microorganism that causes cholera:
Vibrio cholerae
How can cholera be transmitted?
- Through contaminated drinking water
- Infected people are handling food
- Undercooked seafood caught in water polluted with sewage
The incubation period for cholera:
A few hours to a few days
How exactly do the bacteria work to cause cholera?
If the bacteria survive the acidic conditions of the stomach, they enter the intestine where they reproduce and secrete a toxin that upset the functioning of the epithelium lining of the intestine. The toxins cause the loss of water and salts from the blood into the small intestine, resulting in diarrhea so that the body becomes rapidly dehydrated.
Symptoms of cholera:
Diarrhea Feeling weak Rapid heart rate Low BP Muscle cramps
Treatment for cholera:
ORH restores osmotic balance
Prevention for cholera:
Drinking clean water
Building sanitation facilities
Constructing sewage treatment systems
Good hygiene: washing hands, cooking thoroughly
The microorganism that causes typhoid:
Salmonella typhi
How is typhi transmitted:
Drinking contaminated water
Flies transmitting bacteria from faeces to food
The incubation period for typhoid lasts ________
2 weeks
Symptoms for typhoid:
- High fever
- Headaches
- Cough
- Stomach cramps
- Constipation/diarrhea
- Vomiting
- Mental confusion
- Bleeding and holes in the gut/intestine
- Toxins released can cause inflammation of the heart and organ failure
Prevention for typhoid:
Good sanitation and hygiene
Avoid crowded, unhygienic areas
Gonorrhoea is caused by ___________
Neisseria gonnorhoeae
Incubation period for gonnorhoea is _________
A few days long
Symptoms of gonnorhoea:
Half of the people mainly women are asymptomatic: discharge and bleeding between menstrual periods.
If it spreads it ca case the women to become infertile
Most men show symptoms: discharge of pus and pain while urinating
General symptoms: fever and headaches
Treatment for gonnorhoea:
Antibiotics or a combination of antibiotics
A major concern with treating gonnorhoea:
The bacterium is evolving to become resistant to antibiotics
Treatment for typhoid:
Antibiotics: penicillin
Vaccines
Pathogenic fungi cause infections of the ________
skin or nails or mucus membranes: vagina/mouth
How does the fungus work to cause athlete’s foot:
Fungal spores may be transferred from the air or floor to the skin
The fungus feeds on the outer layer of the skin. A bad infection causes sore, raw patches that may become infected by other organisms
Treatment for athlete’s foot:
The immune system will cure it
Antifungal drugs
Measure to prevent athlete’s foot:
Avoid changing rooms
Wear cotton socks and loose-fitting shoes
Keep toenails cut short
Do not wear shoes that were previously worn during the infection again
Cause of malaria:
Malaria is caused by Plasmodium and due to the transfer of malarial parasite by the Anopheles.
The Anopheles transmits the malarial parasite to her saliva when she sucks blood
The life cycle of the Anopheles mosquito:
Adult ➡ Lays eggs ➡ Larva ➡ Pupa
The life cycle of the malarial parasite:
An uninfected mosquito feeds from an infected person and takes in sex cells
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Fertilisation occurs and the zygotes develop into malarial parasite
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The infected mosquito injects malarial parasite into the bloodstream
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The parasite enters liver cells and changes form. It spends around 2 weeks to several months in the liver.
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The new form ruptures the liver cells, escapes into the bloodstream, and infects RBCs
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Infected RBCs burst and release more parasites and sex cells
Symptoms of malaria:
Alternating cold sweats and fever
Vomiting
Joint pains
Anemia
Coma and death, esp. in young children
Measures to control the spread of malaria:
Using insecticides
Introducing a fish called Tilapia into ponds
Using insect repellents, wearing long-sleeved shirts, and sleeping under mosquito nets
Draining swamps and pools
Using drugs to target the various stages of the protozoan’s life cycle
Treatment for malaria:
Drugs: quinine from the bark of the cinchona tree
Anti-malarial drugs: kill the pathogen or prevent it from reproducing in the body. Others reduce the symptoms
A general immune response is the work of ________
A specific immune response is the work of ________
- Phagocytes
- Lymphocytes that produce antibodies
The 2 general purposes of antibodies:
- Neutralising the target threat: cause bacteria to burst open OR bind to bacterial toxins in the blood, which neutralizes them
- Recruiting other cells and chemicals to combat the threat: act as markers OR cause bacteria to clump together, therefore, becoming inactive and easily killed by the phagocytes
What do memory cells do?
They provide us with long-lasting immunity
Meaning of active immunity:
The body makes its own antibodies
Meaning of passive immunity:
The body receives antibodies
How can immunity be maintained?
Booster injections
Examples of natural antibiotics (antibiotics produced by bacteria and fungi):
*anti-biotics are chemicals that kill microorganisms or reduce their growth
Penicillin
Streptomycin
Chloramphenicol
Two types of antibiotics based on their function:
Bactericidal (kill bacteria) eg. penicillin (interferes with the manufacture of bacterial cell wall which weakens it and water enters by osmosis and osmotic lysis) and tetracycline (interferes with protein synthesis which stops the enzyme production)
Bacteriostatic (stop them reproducing) eg. nalidixic acid (interferes with DNA replication making cell division impossible so bacteria cannot multiply)
How do bacteria become resistant?
A random gene mutation makes the bacteria resistant to a specific antibiotic. In a place where the antibiotic is widely used, the resistant-bacteria will have an advantage over the non-resistant-bacteria and will survive and multiply more than the non-resistant type
This soon results in a population of millions of resistant bacteria
The purpose of sewage treatment:
- To get rid of the microorganisms
- To remove the solid waste and suspended organic matter
Describe the percolating filter method:
Screening to remove large objects ⬇ Settling tanks ⬇ Influent ⬇ Rotating sprinkler over the filter bed ⬇ Filter bed: stones covered with protozoa, fungi, and aerobic bacteria, and larger invertebrates ⬇ Effluent (treated sewage) is released into a waterway
Describe the activated sludge method:
Screening to remove large objects ⬇ Settling tanks ⬇ Influent ⬇ Aeration tanks: activated by O₂. Bacteria oxidize the organic material ⬇ Sedimentation tank ⬇ Some returns to the activated sludge: add bacteria ⬇ Effluent
How is the waste sludge in settling tanks treated?
Anaerobic digestion by microorganisms in a fermentation tank
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Biogas (methane + CO₂) by methanogens
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Fuel: electricity and heating
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The remaining dry solid material can be used as fertilizers/disposed of in landfill sites
