Bacterial pathogens Flashcards
What is reductive evolution and what does it lead to?
Reductive evolution is the process by which microorganisms remove genes from their genome. It can occur when free-living bacteria enter a restrictive state (either as endosymbionts or parasites) or are completely absorbed by another organism becoming intracellular (symbiogenesis). This leads to genome degredation and genome reduction. Genome degredation is the process where by pseudogenes are lost as a result of being redudant now that the bacteria is using host cell machinary. Over time the bacteria loses non-functional DNA which leads to genomes reduction where we see bacterias with very small genomes (e.g. syphillis)
In bacterial populations what is the difference between clonal and panmictic structures?
Clonal populations have no horizontal gene transfer while panmictic does. Clonal structures are less common, one example is TB.
JB: I don’t really know this one?!
AB: This is all there is too it I think.
Why are biofilms important?
Bacterial biolfims are produced when individual cells change to multicellular communities allowing them to be more resistant physcially and metabolically. Chitin plays an important in the formation and surface attachment of biofilms. Cholera is one example that produces biolfilm in acquatic environments.
What is a bacteriaphage and how can it be beneficial for the bacterium?
bacteriaphages are viruses that affect bacteria. This can be beneficial as bacterias can gain novel DNA material through bacterial transduction, transformation and conjugation which creates diveristy. Genes for cholera toxin is carried on a temperate bacteriophage.
What is the principle of vaccine escape?
Imperfect vaccines can lead to the emergence of new mutants that escape the vaccine. Capsule switch is a mechanism of immune and vaccine evasion that helps bacteria with polysccharide capsules either lose or gain capsules, increasing transformation.
What is phase variation?
Phase variation is one of the main mechanisms that leads to antigenic variation in bacterias. E.g. the pilE gene can produce different pilE proteins and phase variation turns genes encoding the antigen (like pilE) on or off to vary the pilus which has a simialr function as the viral spike protein. Its a random and reversible process. The number of tandem repeats will determine whether it is “on” of “off”.
