Week 3 - Intro to Microbiology and Bacteria Flashcards
What are the types of Microbes
- Bacteria
- Viruses
- Parasites
- Fungi
- Prions
What’s the difference between Prokaryotes and Eukaryotes
- Prokaryotes are always unicellular while eukaryotes are often multi-celled organisms.
- Eukaryotes are more complex and larger cells than prokaryotic cells
- DNA in eukaryotes is stored within a nucleus while DNA is just floating freely in the cytoplasm of prokaryote cells
What is bacteria
Bacteria are small prokaryotic organisms that are found in every habitat on earth
Example of bacteria
E. Coli
Strep mutans
What are the main characteristics of bacteria
- capsules
- endospores
What is this structure and its function
Flagellum
Acts like a tail and propels the bacteria through substances
What is this structure and its function
Capsule
- Serves as a shield which protects the cell from physical evade the host immune system.
- The ‘stickiness’ of the capsule promotes cell adhesion to surfaces, a survival advantage.
What is this structure and its function
Cell Wall
- Complex semi rigid structure used to separates the exocellular and intracellular environments
- It’s also important in maintaining osmotic pressure and prevent the cell from popping
- Gram positive cell walls
- Gram negative cell walls
What is this structure and its function
Cell membrane
Flexible semipermeable phospholipid bi layer which regulates the transfer of particles into the cell
What is this structure and its function
Fimbriae
Fimbriae are long filamentous polymeric protein structures located at the surface of bacteria cells. They enable the bacteria to bind to specific receptor structures and thereby to colonies specific surfaces.
What is this structure and its function
Plasmids
Additional genetic information which can be used by the bacteria or transferred to another bacteria through congregation. This can provide a survival advantage.
What are endospores
Endospores are formed by certain bacteria. They are released when environmental conditions are unfavourable which forces the bacteria into a dormant state that lasts until conditions become favourable again.
E.g. Clostridium tentani (Tetanus)
What’s the structure of a gram positive cell wall
- A thick layer of peptidoglycan
- Plasma membrane
- Has teichoic acid
- Turns purple after gram stain due to the thick peptidoglycan which can hold the stain well
What’s the structure of a gram negative bacterial cell wall
- Thin layer of peptidoglycan
- Outer cell membrane
- Porins
- Lipopolysaccharides (LPS)
- Turns pink after gram stain because the thin peptidoglycan layer doesn’t hold the purple stain well.
What are the Macromolecules of the Cell Wall
- Peptidoglycan
- Teichoic Acid (only in gram positive)
- Lipopolysaccharides (LPS) (only in gram negative)
What are the different shapes of bacteria
- Coccus (sphere)
- Bacillus (rod)
- Spirochete (spiral) - don’t really need to know
What macromolecule is found in gram indeterminant bacteria cell wall
Mycolic Acid
What are the phases of bacteria growth
- Lag time
- Exponential phase
- Stationary phase
- Death phase
Explain lag phase in the phases of bacteria growth
The initial phase where the bacteria are adjusting to their environment and the bacteria are not dividing.
Explain exponential phase in the phases of bacteria growth
Period of rapid cell division (binary fission), bacteria multiplies at a constant rate, leading to a logarithmic growth
Explain stationary phase in the phases of bacteria growth
Stage where nutrients become limited, waste product accumulates or other environmental factors impact growth. Growth rate slows and the number of new cells being producing equals the number of cells dying causing population to stabilize
Explain death phase in the phases of bacteria growth
Number of dying cells exceeds the number of new cells produced and conditions become increasingly unfavorable for bacteria growth leading to the decline in population. At this stage endospores may be released to make the bacteria dormant.
What factors impact bacteria growth
Main
-pH
- Water and osmotic pressure
- Oxygen and atmosphere
Others
- nutrients
- temperature
*all bacteria require different requirements
What are Obligate Anaerobe
Bacteria which don’t grow in oxygen
e.g. Prevotella
What are Aerobe
Bacteria which requires oxygen to survive
e.g. Myobacterium tuberculosis
What are Faculative Anaerobes
Bacteria which can grow with or without oxygen
e.g. staphylococcus spp
What are aerotolerant bacteria
grows in the presence of oxygen but doesn’t use it.
e.g. Lactobacillus
What is Microaerophilic bacteria
Requires low levels of oxygen
e.g. Neisseria spp
What is capnophilic bacteria
Requires CO2
e.g. Campylobacter jejuni
How do bacteria reproduce
Binary Fission - process by which prokaryotic organisms divide and reproduce
Explain the steps of bacteria reproduction (binary fission)
1.The genetic material (DNA) is replicated
2. Bacteria elongates and the genetic material and organelles move to other sides of the cell
3. A new cell wall forms down the middle of the bacteria cell
4. Two daughter cells pull apart
Why does bacteria horizontal gene transfer occur
- Creates biodiversity in population which increases resilience in the population
- Creates evolutions and mutations such as antibiotic resistance which favours the bacteria population
- transfer of genetic material
- creates diversity in population
- Genes for antibiotic resistance, ability to use new metabolites
What are the types of horizontal gene transfer in Bacteria
- Transformation
- Transduction
- Conjugation
Explain process of transformation (bacteria horizontal gene transfer)
The uptake of free genetic material from the environment. This only occurs if the bacteria is competent (the ability to take up free DNA)
1. Free DNA is transported across the cell membrane and entered a new bacteria cell
2. Homages recombination occurs which is where the foreign DNA aligns with similar sequences in the bacterial genomes and incorporates itself into it resulting in new proteins or the development of new traits
Explain the process of transduction (bacteria horizontal gene transfer)
The transfer of foreign genetic material by a virus
1. A bacteriophage (virus) attaches to a bacteria cell and injects its genetic material
2. The viral genetic material is integrated into the bacteria’s DNA and is directed to replicate the phages DNA and produce new phage particles
3. Occasionally fragments of the bacterial DNA is mistakenly packaged into the new phase particle instead of viral DNA and is released to infect new bacterial cells
4. The phage particle infects another bacterial cell and injects bacterial DNA which is integrated into the gene of the new bacteria. This may lead to the production of new proteins and traits
Explain the process of conjugation (bacterial horizontal gene transfer)
The transfer of genetic material between 2 bacteria using cell to cell contact
- the transfer is unidirectional and the donor cell contains the fertility factor making it a F+ cell and it has the sex pilus structure
1. Donor cell creates physical contact with a precipitant cell using its pilus
2. The pilus creates a channel like structure where the F- plasmid is transferred to the recipient cell
3. The recipient cell now carrying the transmitted genetic material can now express the fertility factor and a F- cell
What are the different types of host microorganism association
- Mutualism
- Commensalism
- Parasitism
- Opportunism
What is mutualism in a host microorganism association
Microorganism and host live together to their mutual benefit
E.g.
Bacteria in stomach of ruminants break down cellulose and in return they receive nutrients
What is commensalism in a host microorganism association
Microorganism benefit while host is unharmed (non of this relationship occurs in humans)
E.g.
Mosses on trees
What is parasitism in a host microorganism association
Microorganism benefits at the expense of the host
E.g.
Most infections caused by microorganisms (bacteria, viruses, parasites)
What is opportunism in a host microorganism association
Microorganisms that would not normally cause an infection, but do so because of an alteration in host or change in environment
E.g.
- Oral bacteria enter bloodstream, causes infective endocarditis - occurs when you floss and cause bleeding opens blood vessels to oral bacteria
- Antibiotic use allows Candida to flourish which causes thrush. Antibiotics will remove a lot of oral microbes which allows the growth of Candida
What is the acid only found in Gram positive bacteria
Teichoic Acid
What is the acid only found in gram negative bacteria
Lipopolysaccharide
Where is it not normal to find any micoorganisms
Blood vessels
What is a Mycoplasma
Type of bacteria with no cell wall but is protected from osmotic pressure as they live inside other cells.
