Microbiology and immune system
Viruses, bacteria, protists, and fungi
V, B, P, F are all:
Hugely diverse group found in all environments.
Occur in vast numbers
Vary in size:
1. Invisible to naked eye – micro-organisms (microbes)
2. Visible – macro-organisms
Acellular (V) or cellular (B, P, F)
Prokaryotes – B
Eukaryotes – F, P
Unicellular or form colonies
Pathogenic and non-pathogenic
Pathogenic – disease causing
Non-pathogenic – harmless
Disease causing = pathogens = germs
Viruses
Infect animals, plants, even bacteria.
Characteristics:
Extremely small – microscopic
Exist in 2 states
1. Virus – when active
2. Virion – when dormant (not in contact with host)
Not living organisms
Only survive inside host cells
Only reproduce inside a living cell
Always associated with disease
Can remain dormant within an organism
Different shapes:
1. Polyhedral – cuboidal
2. Helical – spiral
3. Complex – tadpole
Structure:
Acellular – not a cell
Core of DNA or RNA
Hereditary information not enclosed in a nuclear membrane.
Nucleic acid surrounded by protein coat or capsid.
Some viruses, capsid is covered by an envelope of a lipid bilayer. Used to protect the virus from
host’s nuclease enzyme.
Bacteria
, Unicellular micro-organisms
Group - Monera
General characteristics:
Most diverse and abundant group.
Inhabit all env.
Extremophiles: thrive in climatic or environmental extremes. (Intense heat or cold)
Mostly useful.
Unicellular among the smallest organisms.
Vary in shape:
1. Cocci – spherical bacteria
2. Bacilli – rod-shaped bacteria
3. Spiralla – spiral shaped
4. Vibrios – comma-shaped
Exist singly, in chains or in clumps.
In favorable conditions bacteria reproduce by binary fission.
In unfavorable conditions bacteria can survive dormant.
Structure:
Unicellular
Rigid cell wall
Plasma membrane is a multipurpose structure:
- Serves as mitochondrion, endoplasmic reticulum and sometimes even chloroplast.
- Also controls entry and exit of materials.
Procaryotes
- No nuclear membrane
- DNA does not combine with histone, protein as in eukaryotic cells.
Closed loop of bacteria.
Waxy capsule as outermost layer.
Flagella, enable them to move.
Viruses, bacteria, protists, and fungi
V, B, P, F are all:
Hugely diverse group found in all environments.
Occur in vast numbers
Vary in size:
1. Invisible to naked eye – micro-organisms (microbes)
2. Visible – macro-organisms
Acellular (V) or cellular (B, P, F)
Prokaryotes – B
Eukaryotes – F, P
Unicellular or form colonies
Pathogenic and non-pathogenic
Pathogenic – disease causing
Non-pathogenic – harmless
Disease causing = pathogens = germs
Viruses
Infect animals, plants, even bacteria.
Characteristics:
Extremely small – microscopic
Exist in 2 states
1. Virus – when active
2. Virion – when dormant (not in contact with host)
Not living organisms
Only survive inside host cells
Only reproduce inside a living cell
Always associated with disease
Can remain dormant within an organism
Different shapes:
1. Polyhedral – cuboidal
2. Helical – spiral
3. Complex – tadpole
Structure:
Acellular – not a cell
Core of DNA or RNA
Hereditary information not enclosed in a nuclear membrane.
Nucleic acid surrounded by protein coat or capsid.
Some viruses, capsid is covered by an envelope of a lipid bilayer. Used to protect the virus from
host’s nuclease enzyme.
Bacteria
, Unicellular micro-organisms
Group - Monera
General characteristics:
Most diverse and abundant group.
Inhabit all env.
Extremophiles: thrive in climatic or environmental extremes. (Intense heat or cold)
Mostly useful.
Unicellular among the smallest organisms.
Vary in shape:
1. Cocci – spherical bacteria
2. Bacilli – rod-shaped bacteria
3. Spiralla – spiral shaped
4. Vibrios – comma-shaped
Exist singly, in chains or in clumps.
In favorable conditions bacteria reproduce by binary fission.
In unfavorable conditions bacteria can survive dormant.
Structure:
Unicellular
Rigid cell wall
Plasma membrane is a multipurpose structure:
- Serves as mitochondrion, endoplasmic reticulum and sometimes even chloroplast.
- Also controls entry and exit of materials.
Procaryotes
- No nuclear membrane
- DNA does not combine with histone, protein as in eukaryotic cells.
Closed loop of bacteria.
Waxy capsule as outermost layer.
Flagella, enable them to move.
