| what is horizontal gene transfer and what are the different types? | horizontal gene transfer is the transmission of genes between two already existing cells.
this can be done by conjugation, transduction, transformation |
| how does transduction work? | the transfer of genes is conducted by viruses; bacteriophages.
1. the bacteriophage attaches and infects the bacteria with its own genome.
2. the viral DNA is then integrated in the bacterial genome.
3. when the viral DNA is removed again, it might take some bacterial DNA with it.
4. the virus can infect other bacteria, with that piece of bacterial DNA. |
| how does conjugation work? | 1. the donor bacteria contains the fertility factor on the F plasmid
2. the donor forms an extending structure towards the recipient; the sex pilus
3. one of the strands of the F plasmid is transferred
4. replication of the F plasmid takes place in both bacteria |
| how does transformation work? | it is the uptake of free genetic material by competent bacteria |
| what is plasmid incompatibility? | two plasmids with the same replication mechanism can't be present in the same bacteria |
| what is the function of transposons? | they are jumping genes that can transfer DNA from one position in the bacterial genome to another |
| what are the three types of transposons? | insertion sequences: simple transposons, only contain the minimal genetic information needed for its own transfer
composite transposons: complex transposons, contain a central region with insertion sequences flanking it, contain genes for antibiotic resistance etc.
non-composite transposons: complex transposons, contain genes for antibiotic resistance etc. but have no insertion sequences flanking them |
| what is the function and composition of integrons? | integrons promote expression of certain genes by shuffling them
they compose of an Intl gene, a recombination site where gene cassettes can be inserted and a promotor. |
| what are the differences between commensal, primary and opportunistic bacteria/pathogens? | commensal bacteria: not pathogenic, aid in digestion, produce vitamins, activate immune response
primary pathogens: bacteria that will always cause disease
opportunistic pathogens: bacteria that will only cause disease when the host's immune system is weak |
| what are the virulence factors? | capsule, biofilm, adherence, invasion, by-products of growth, toxins, degradative enzymes, cytotoxic proteins, endotoxin, superantigen, intracellular growth, resistance to antibiotics, evasion of phagocytosis and immune clearance, induction of excess inflammation |
| how do bacteria adhere to the body surfaces? | they use adhesins on the tips of their fimbriae to bind to the sugars of the surface, these adhesins are also called lectins.
they can also form a biofilm when there are enough bacteria; quorum. this is determined by quorum sensing |
| how do bacteria destroy tissues? | they have toxins that can be released and become exotoxins. most exotoxins have an A and B subunit (B for binding and A for injury (action)).
they also have endotoxins, which are released when the cell lyses.
they have superantigens that activate T cells without there being an antigen. this promotes shock, life-threatening fever etc. |
| what does EHEC stand for and what are its adhesins and toxins? | EHEC -> enterohemorrhagic E. coli
adhesins: bundle-forming pili (BFP), intimins
toxins: Shiga toxins 1 and 2, verotoxin |
| what does EPEC stand for and what are its adhesins and toxins? | EPEC -> enteropathogenic E. coli
adhesins: bundle-forming pili (BFP), intimins
toxins: / |
| what does UPEC stand for and what are its adhesins and toxins? | UPEC -> uropathogenic E. coli
adhesins: P pilli, Dr fimbriae
toxins: hemolysin HlyA |
