Bio 11 microbiology
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Bio 11 microbiology
micro organisms, viruses, bacteria
Who discovered viruses?
Dmitri Iwanowski : Found that juice in tobacco leaves caused infections in other plants
: Realized tiny particles in juice that caused infection
-named particle "virus" which means infection
What is the definition of Virus?
-Non-cellular particle made of genetic material and protein that can invade living cells.
Structure: components of a virus
1. Core of nucleic acids (DNA, RNA)
2. protein coat (capsid) that surrounds nucleic acid
*some have more complex structures.
What is a bacteriophage?
-Virus that infects bacteria
Diversity in structure: what are the shapes of viruses?
Average size of virus?
between 10-300 nm. (nano-metres)
* must use scanning electron microscope or transmission electron microscope
Why are viruses specific?
-Can only infect a specific host
ex: HIV specific to humans
Are viruses living?
Viruses are obligate intercellular parasites.
(must feed off of host cell)
Living Characteristics of viruses?
Non-living characteristics of viruses?
-doesn't use energy
What are viral infections?
-Causes infections by injecting DNA into host
What are the 4 general phases of viral infection?
What are the two different ways viruses can infect cells?
1. Lytic infection
2. Lysogenic infection
What is the main difference between Lytic and Lysogenic infection?
- Growth phase of Lysogenic infection:
*Viral DNA is incorporated into host DNA (prophage)
-remains dormant for a long period of time
-cell replicates viral DNA by binary fission
What happens during infection phase ?
-virus attaches to host cell using tail fibres
-inserts DNA into cell
What happens during the growth phase of Lytic infection?
-Host's RNA polymerase (enzyme) make MRNA from viral DNA
-MRNA takes over host cell
What happens during the replication phase?
-virus uses host's machinery (ribosomes, golgi apparatus etc) to construct :
2) Capsids (protein)
What happens during the lysis phase?
-Host cell becomes filled with new viruses....then bursts (lyse)
- Spreads viruses to neighbouring cells.
How long can a Lytic infection occur in?
What is the origin of viruses?
-evolved after first living cell (because must live inside host)
- evolved from genetic material of living cells, mutated and evolved
What are the advantages of viruses?
- genetic research (cancer)
- Gene therapy
- genetic engineering (injecting specific DNA)
What are the disadvantages of viruses?
1. Disease (HIV, Influenza) viruses are pathogens
- during infection when DNA is inserted, gene may become an oncogene causing cancer
-cell undergoes uncontrolled divisions forming tumor (benign or malignant)
How can you prevent viral infections?
1. good hygiene
2. Healthy lifestyle (diet, exercise)
What are the two lines of defence against viruses?
1. Non-specific defences
2. Specific defenses
What are the non specific defences and what do they do?
- skin (oil and sweat provide acidic environment)
-cilia/mucus (traps virus)
-secretions (destroys virus)
-phagocytes (engulf bact/viruses -> leads to fever)
-interferon (infected cell produces protein that interferes with virus & slows it)
What are the specific defences against viral infection?
1. Antibodies/immune response
3. Cell mediated immunity
How do antibodies/immune response defend against viral infection?
Pathogen specific antibodies are produced that bind to and inactivate virus (antigen)
How does immunity defend against viral infection?
: injection of vaccine that causes body to produce antibodies
: injection of antibodies produced in another animal
How does cell mediated immunity defend against viral infection?
Killer T-cells attack antigen-bearing cells and destroy them
What are the main differences between prokaryotic and eukaryotic cells?
Prokaryotic cells do not have a nucleus, or membrane.
How are monerans classified?
-all monerans are prokaryotic
- All called bacteria
- Divided into 4 phyla
What are the 4 phyla that monerans are divided into?
What are the characteristics of Eubacteria?
- surrounded by cell wall composed of complex carbs
- within cell wall is membrane
-some have flagella
what are the characteristics of Cyanobacteria?
-found on water+land
-first to recolonize after nat. disaster
characteristics of archaebacteria?
-live in extremely harsh environments
characteristics of prochlorobacteria?
-contain chlorophyll A and B as principal pigments
- similar to chloroplasts of plants
-only 2 species discovered
What are the three cell shapes of monerans?
What are the characteristics of Bacilli?
-produce endospores (dormant, waiting for ideal conditions)
what are the characteristics of Cocci?
-grow in colonies of two cells
- clumps or clusters
what are the characteristics of spirilla?
- possess bipolar tufts of flagella
What are the different types of bacterial movement?
- propelled by flagella
- lash, snake, spiral forward
- glide on slimelike material
- sessile (no movement)
What are the two major ways bacteria obtain energy?
How do Autotrophic bacteria obtain energy?
a) Phototrophic autotrophs : obtain energy from sunlight
b) chemotrophic autotrophs: live in harsh environments, obtain energy from inorganic molecules
How do heterotrophic bacteria obtain energy?
a) chemotrophic heterotrophs: Break down organic molecules, most bacteria and animals
b) phototrophic heterotrophs : Photosynthetic but also need organic compounds
How can we look at the composition of the cell wall?
using gram staining
what 2 chemicals are used for gram staining?
crystal violet (purple)
What does it mean when bacteria takes up the crystal violet chemical?
eg. clostridium tetanus
what happens when bacteria take up the safranine chemical?
*more toxic, more resistant to antibiotics
eg: e coli.