5.2 Microbial adaptations Flashcards
Define microbial adaptation
ability of microbes to endure the selective pressures of their environment.
Give 3 ways in which microganisms adapt
1) replicate at a very fast rate in a very short period of time
2) change genetic makeup very quickly
3) large number of them also allows selective choices of gaining virulence from one and other
label this diagram
Describe the 3 types of horizontal transmission by bacteria that allow transfer of genetic information
1) Conjugation; bacteria-bacteria transfer
2) Transduction; viral-mediated transfer (of genetic info between bacterium)
3) Transformation; free DNA transfer (involves changing the permeability of the bacterial cell capsule/wall to share free DNA)
What method of gene transfer does this image show and briefy explain it
Conjugation
1) bacteria A meets bacteria B and through pili the bacteria connect and create passageway
2) a number of molecular mechanisms in bacteria A produce proteins that allow transfer of material + conversion of genetic info from the circular plasmid into a single length of extracellular DNA
3) this is then replicated and transferred from bacteria A to bacteria B through pili
4) Bacteria B is now in possession of new gene and has proteins which allow it to be expressed
How does a bacteriophage initially enter a cell?
Following this what are the two life cycles the phage can follow?
1) virus adheres to bacteria (virus + bacteria = bacteriophage)
2) Bacteriophage specialised to have a capsid head (containing genetic info) and a very strong centre coil
3) via a series of movements and contractions it injects its centre (containg genetic info) through the cell surface
4) This causes the virus RNA/DNA to be injected into the bacteria and incorperated into the host cell
5) It will then either follow the lytic or the lysogenic cycle
Describe the LYTIC cycle of a bacteriophage
1) Attachment: the phage attaches to the surface of the host
2) Penetration: the viral DNA enters the host cell + digests host DNA
3) Biosynthesis: phages DNA replicates (capsids and virulence factors) using host machinery to form phage proteins
4) Maturation: many daughter phage particles are assembled
5) Lysis: the host cell is weakened and lyses occurs releasing newly made bacteriophages into circulation
Describe the LYSOGENIC cycle of a bacteriophage
1) Attachment: the phage attaches to the surface of the host
2) Penetration: the viral DNA enters the host cell BUT becomes integrated into the host DNA using integrases
3) Replication: It is replicated along with host genome, as the host cell divides as does the newly integrated phage DNA which means it is passed on to host daughter cells
4) Dormancy: this continues and the phage remains dormant within host until environment is suitable OR it acquires the correct proteins to allow it to transition into the lytic phase
What is transduction and what are the 2 types that can occur to transfer genes, compare these
When genes from a host cell bacteria are incorporated into the genome of a bacteriophage and then carried to another host cell when the bacteriophage initiates another cycle of infection
1) Generalised transduction: associated with the lysogenic cycle
* the bacteriophages can pick up ANY portion of the host’s genome
2) Specialised transduction:
* the bacteriophages pick up ONLY specific portions of the host’s DNA
What is Transformation and how does it assist bacteria in gene transfer?
Give an example of when this may occur
Movement of genetic information from a donor cell to a recipient cell
Done by changing permeability of the outer capsule allowing the bacteria to take up the genetic information
Example: In the gut we have bacteria, some of which will be dying. This creates a slushy solution which causes their membrane to become less rigid allowing genetic information to be taken up by other bacteria into their cell
Why would bacteria produce antibiotics?
Remember an antibiotic is a chemical produced by a micro-organism that kills or inhibits the growth of other micro-organims
Hence bacteria will produce antibiotics to to target processes essential to other bacteria in order to compete with them in the environment
Copare antibiotic resistance to antimicrobial resistance
Antibiotic resistance: refers specifically to the resistance to antibiotics that occurs in common bacteria that cause infections
Antimicrobial resistance: is a broader term, that also includes resistance to other drugs that treat infections caused by other microbes (bacteria, parasites, viruses and fungi)
Remember all antibiotics are antimicrobials but not all antimicrobials are antibiotics
Name the 3 ways bacteria can become antibiotic resistant
1) Enzymatic Degradation:
- an existing cellular enzyme is modified to react with the antibiotic in such a way that it no longer affects the microorganism
- eg. B-lactamase inhibits Penicillin binding
2) Efflux pump:
- these are naturally found within the bacteria and help them to pump out metabolites.
- If bacteria can identify the specific genetic information encoding specific antibiotics, they can be recognised and pumped out
3) Target resistance: changes in cell wall shape
- genes expressed by bacteria may encode proteins that either give protection of the target site or modifications in the target site
- results in decreased affinity for the antibiotic molecule
Briefly describe the WHO’s 5 step action plan to target antibiotic resistance
1) Improve awareness and understanding of antimicrobial resistance
2) strengthen knowledge through surveillance and research
3) reduce the incidence of infection
4) optimize the use of antimicrobial agents
5) Investing in innovation, supply and access to tackle AMR
Name three ways bacteria can become resistant to antibiotics on a molecular level
1) Develop point mutations in one of the target genes
2) Acquire plasmids or transposons through macro-evolutionary changes
3) Acquir DNA from an exogenous source (i.e Neisseria can acquire DNA from the environment)
