Microbiology 1 Flashcards
Define microbiology?
- The study of microorganisms
- Micro = small
- Biology = the study of living things
What is microbiology important for?
- Medicine
- Environmental science
- Food and drink production
- Fundamental research
- Agriculture
- Pharmaceutical industry
- Genetic engineering
Describe the process of producing antibiotics.
- Produced from microorganisms
- Antibiotics are isolated from natural microorganisms by the process of fermentation
- Many microbial cells convert raw materials or substrate into valuable organic compounds
- microbial cells produce intracellular and extracellular enzymes important for the success of pharmaceutical fermentation process
Define eukaryotic cells.
Any cell that contains a clearly defined nucleus and membrane bound organelles
Define prokaryotic cells.
Any unicellular organism that does not contain a membrane bound nucleus or organelles
Describe DNA replication of eukaryotic cells.
Highly regulated with selective origins and sequences
Describe DNA replication of prokaryotic cells.
Replicates entire genome at once
Describe how antibiotic resistance spreads. (from animals)
Animals get antibiotics and develop resistance in their guts
- Drug-resistant b bacteria can remain on meat from animals - when not handled or cooked properly, the bacteria can spread to humans
- Fertiliser or water containing animal faces and drug-resistant bacteria is used on food crops
- Drug-resistant bacteria in the animal faces can remain on crops and be eaten - these bacteria can remain in the human gut
- Resistant bacteria spreads further in the community
Describe how antibiotic resistance spreads (starting from humans).
- Person gets antibiotics and develops resistant bacteria in his gut
- Person stays home and in th general community and spreads resistant bacteria
- Person gets care at a hospital, nursing home or other inpatient care facility
- Resistant germs and bacteria spread to other patients and healthcare providers within the healthcare facility
- Resistant bacteria spreads further in the community
Describe the bacterial cell wall.
Thick and rigid due to peptidoglycan (murrain)
What are the two distinct structural types for bacterial cells?
Gram negative - does not retain dye methyl violet
Gram positive - retain the stain
State the two major roles of the bacterial cell wall.
a) to protect the cell against osmotic rupture particularly in dilated media and also against certain possible mechanical damage
b) To assign bacterial shapes, their subsequent major division into Gram positive and gram negative microorganisms and their antigenic attributes
Describe the structure of gram-negative cells.
- Have much thinner layer of peptidoglycan, making the wall less sturdy
- The structure is made more complex by the presence of a layer of lipoprotein, polysaccharide and phospholipid known as the outer membrane
Describe the structure of gram-positive cells.
- Relatively simple in structure
- Comprising several layers of peptidoglycan connected to each other by cross-linkages to form a strong, rigid scaffolding
- Contain acidic polysaccharides called teichoic acids
- Phosphate groups impart on overall negative charge to the cell surface
How do most bacteria grow?
Binary fission - one cell undergoes division to give rise to the formation of two cells
Describe the lag phase.
- First phase characterised by cellular activity and increase only in cell size
- Transition phase to the exponential phase AFTER initial phase doubled
- Physiological adaptation of the cell to culture conditions
Describe the exponential phase.
- Second phase of growth
- Cells actively dividing by binary fission and their number increases exponentially
- Increase of cells in culture is proportional to the number of cells present at any particular time
Describe the stationary phase.
- Third phase of growth
- Total number of live cells reaches a plateau
- The number of new cells created by cell division is now equivalent to the number of cells dying
Describe the death phase.
- The number of dying cells exceeds the number of dividing cells, leading to an exponential decrease in the number of cells
How does temp. affect microbial growth?
most microorganisms achieve optimal growth at ‘middling’ temps around 20-45 degrees - these are called mesophils
How does pH affect microbial growth?
Most microorganisms grow best around neutrality (pH 7)
How does oxygen affect microbial growth?
(A) must grow at or near the surface, where oxygen is able to diffuse.
(B) able to adjust their metabolism to the prevailing oxygen conditions.
(C) occupy those zones where no oxygen is present at all.
(D) do not use oxygen, but neither are they inhibited by it.
(E) have specific oxygen requirements, and can only grow within a narrow range of oxygen tensions
Describe how osmotic pressure can affect microbial growth (isotonic solution)
- No net movement of water particles
- Cell membrane is attached to cell wall
Describe how hypertonic solution can affect microbial growth.
- Water particles move out of the cell
- Cell membrane shrinks and detached from cell wall (plasmolysis)
Describe how a hypotonic solution affects microbial growth.
- Water particles move into the cell
- Cell wall counteracts osmotic pressure to prevent swelling and lysis
How does light affect microbial growth?
Phototropic organisms require light in order to carry out photosynthesis
What are the different type of media used to grow bacteria?
- chemically defined media
- selective media
- enriched media
- differential media
What is chemically defined media?
Contain only chemically known components
What is selective media?
Favour the growth of some microorganisms while inhibiting others.
What is enriched media?
Contain added essential nutrients a specific organism needs to grow
What is differential media?
Help distinguish bacteria by the colour of the colonies or the change in the medium.
