LO 1 Flashcards
What are the four groups of microorganisms?
Protozoa, Fungi, Bacteria, Viruses
What is a microorganism?
An organism that is too small to be seen without the aid of a microscope - simple in structure and often unicellular
Define: Protozoa
- Unicellular creature that moves by flagella or in ameboid motion - Has a nucleus and a plasma membrane - Live in water and soil, by feeding on bacteria and sm particles
What is a Giardia infection?
‘Beaver fever’ disease - the Protozoa attach to the intestinal wall by two sucking discs and cause diarrhea **antiprotozoal drugs are used as treatment
Define: Amoebae
A type of Protozoa - can invade the intestinal wall causing diarrhea and move into deeper tissue - in poor countries with poor sanitation - move by pseudopods, no flagella
Define: Fungi
A non-photosynthetic plant - has a nucleus and is enclosed by a rigid cell wall
What are the two types of fungi?
Yeasts and moulds
What is candida?
Candida sp. is a yeast disease that may cause vaginal discharge, skin infections, pneumonia and even death **antifungal drugs are used as treatment
Define: Yeasts
Unicellular oval structures that reproduces by budding
What type of infections are caused by moulds?
Atheletes foot and ringworm are infections caused by the fungus mould **antifungal drugs are used as treatment
Define: Moulds
Multicellular structure that form visible clumps of growth - Moulds start with long tubular structures (hyphae) that produce spore (responsible for the blue green color)
Define: Bacteria
Unicellular organisms typically surrounded by a rigid cell wall - No organized nucleus but can grow and reproduce
What can bacteria cause?
- Strep throat is caused by the bacteria streptococcus which cause skin abscesses called boils - Food poisoning is caused by the bacteria salmonella from poultry ** bacterial infections are treated with antibiotics
T or F: there is bacteria in our pee
False; there is no bacteria in our pee, it’s sterile
Define: Viruses
-Smaller than bacteria and have a very simple structure - unable to grow and reproduce on their own and must rely on a living host cell to replicate the viral parts - animal, plant and bacterial cells serve as host cells for viruses
What are some diseases caused by viruses ?
- Influenza and colds are viral infections - hepatitis, rabies and aids are more serious viral infections ** viral infections are treated with antiviral drugs
How are microorganisms measured?
In metric units called micrometers * 1 micrometer = 0.001 of a millimetre ** all microorganisms are smaller than 0.1mm=100 micrometers
*Micrometre= um
* 1000 micrometres in 1 millimetre
What is the size of a Protozoa? Fungi? Bacteria? Viruses?
Protozoa = 15-20 micrometers Fungi = 5-10 micrometers Bacteria = 0.3-5 micrometers Viruses = 0.02-0.2 micrometers
What is the most common microorganism found in the hospital setting?
Bacteria
Bacteria:
Cocci (pleural) or Coccus (singular)
Spherical or round cells
Bacteria:
Rods or Bacilli (Bacillus=singular)
Rectangular shaped boxes
Bacteria:
Spirilla (Spirillum=singular)
Curved or spiral shaped rods
How can bacteria be divided based on their gram stain?
1) Gram positive - dark bluish-black or purple colour
2) Gram negative - pink-red colour
Why is the Gram reaction important? (3 reasons)
1) Identification - by gram stain and shape, 6 groups (ex. gram positive cocci, gram negative cocci)
2) Effectiveness of certain antibiotics - Penicillin G kills gram positive bacteria, but not gram negative bacteria
3) Effectiveness of certain disinfectants
Define: Endospores
A structure formed by some bacteria that allows the bacterium to remain dormant for years without nurtients or moisture
* More resistant to destruction then vegetative bacteria
A small number of Gram positive rods that are able to produce a special type of spore within the bacterial cell
- bacteria in dust, cereals, grains, and soil exist as endospores
Define: Vegetative cells
Bacterial cell that do NOT contain endospores
* Gram positive rods that are able able to form spores can still exist as vegetative cells when they are actively growing and multiplying
Define: Sporulation
- Stress on cell
- Happens when certain nutrients are depleted
- One copy of the genetic material and a tiny amount of cytoplasm is enclosed by a layer of insulating material and the whole structure is covered with several compact layers of spore coat
Vegetative cell –> Endospore formation in cell –> free endospore
Define: Germination
Spore –> Germination –> Vegetative cell
The process where a endospore germinates into a vegetative bacterium cell when moisture and nutrients are provided
Endospores have a significant impact on ____ and ______
Sterilization and disinfection
What are endospores resistant to?
1) Heat - most bateria are killed by heat of 60-80 degrees Celcius for 10 mins; BUT spores need to be exposed to heat of 121 degrees Celcius for 12-15 minutes for destruction
2) Disinfectants - can only kill endospores with high level of disinfectants after being used for extended periods of time
Define: Binary Fission
The process by which bacteria reproduce
- Elongation, Replication (of genetic material), Genetic material (moves to each end of cell as it grows inward), Seperation of cell (into 2 daughter cells)
Define: Generation time
Time for binary fission to take place; time for population to double
- Can be affected by temperature and the available nutrients
- With ideal condition= 15-20 minutes
- the quicker the generation time, the quicker the onset of symptoms
Define: Colony
A visble mass of bacteria on a solid medium that have grown from one bacterial cell
Define: Growth curve
The phases of growth (lag, log, stationary, death) bacteria go through when introduced into a culture medium
Growth curve:
Define: Lag phase
Phase where bacteria are placed in a new environment and there is little to no increase in numbers for a short period of time
* cells are adapting to their new environment
- lag phase time varies
- Lag phase is 2 hours in food which means it can be left out for 2 hours before bacteria begin to grow
**Also called incubation period where there are no symptoms
Growth curve:
Define: Log phase
Period of maximum growth of bacteria
- cells are dividing at a constant rate
**also called Acute stage: Full blown symptoms; also part of incubation period
Growth curve:
Define: Stationary phase
Phase where bacteria exhaust their supply of nutrients and stop growing and multiplying
* # of live bacteria stays constant during this period
*Symptoms are no better, no worse but still no sign of recovery
Growth curve:
Define: Death phase
Phase where the bacterial cells start to die and the number of live cells decreases
-most die in a short amount of time, others can linger for years
*Those that survive the longest are the ones that form spores
**Also called convalescent period where the symptoms subside and it covers the time until complete recovery
How do viruses vary from bacteria?
1) They are obligate intracellular parasites and only multiply when inside a living host
- Can’t grow in foods, water, bacterial culture or medications
2) They contain a single type of nucleic acid (either DNA or RNA) *other forms of life contain both*
What are viruses composed of?
1) They possess a protein coat surrounding the nucleic acid
2) Some also have an envelope composed mainly of lipids, while others have spikes protruding from the lipid envelope.
*Lipid viruses are generally easier to kill with disinfectants
What has to happen in order for animal virsues to multiply?
1) In order for a virus to multiply in a host, it must attach to complementary receptor sites on the surface of the host’s cells
2) The virus is then taken in by endocytosis where the membrane folds inwards trying to contain the virus
3) As the host cell attempts to destroy the contents of the vesicle, the outer protein coat is digested and the nucleic acid is released inside the host cell
Multiplication of a DNA virus
p.11
Infection of a host cell with virus usually kills the host cell due to which 3 things?
1) Lysis of the cell when it fills with virus particles
2) Diversion of the cell’s metabolic pathways to the manufacture of viral particles
3) Destruction of the virus-infected cell by the lymphocytes of the cellular immune system
Define: Oncogenic viruses
Viruses that can alter the nucleic acid of the host cell in such a way that the cell is transformed to a tumour cell
- ex. hepatitis B virus because it can lead to liver cancer
Do antibiotics have an effect on viral replication?
NO; antibiotics are directed against metabolic pathways of bacteria NOT viruses
Are there many drugs used to inhibit the replication of viruses?
No because they cannot be used or they would destroy host cells
- only a few antiviral drugs such as Acyclovir to control genital herpes
Enveloped virus vs. Unenveloped (naked) virus
Enveloped - a virus particle surrounded by a lipid envelope
Unenveloped - a virus consisting of nucleic acid and protein but no lipid envelope
