Lecture 2 Flashcards
How can bacterial store their genomic information?
Mostly circular, but occasionally, linear chromosomes and plasmids.
Bacteria can have one or multiple chomosomes.
What range of bacterial genome sizes exist?
0.14Mb to 14.3Mb
What usually underpins bacteria having larger genomes?
Needing more genes because you live in more complex environments
What is the common bacterial genome size?
Between 2 and 6Mb
How do bacterial genomes acquire new genes?
Genes that are remnants of phage attack can be found in bacterial genomes
Bacteria will naturally take up DNA form their environment (are transformable)
What is the core genome?
Core genome - Genes that are seen in all strains of the species
What is the dispensable genome?
Genes that are present in two or more strains
What are unique genes?
Genes that are specific to an individual strain
What is the pan-genome?
The pan-genome is the full complement of genes in a clade.
Made up of the core genome, dispensable genome and unique genes.
What is reductive evolution?
Loss of genes that are no longer required
e.g. Evolution of extracellular bacteria that have become intracellular; in which they lose genes that are now superfluous in their new environment.
What are pseudogenes?
Genes which have lost their ability to be expressed; an outcome of reductive evolution
What can cause rapid emergence of genetically uniform pathogens form variable ancestors?
Genetic bottlenecking
Individuals acquire new trait which makes them more likely to survive. Outcompete other individuals untill only pathogen with that trait surviving
Why are the genomes of pathogenic bacteria commonly smaller than non-pathogenic bacteria?
Narrower functional range
What stages does a bacteria go through from being free-living and extra-cellular to being an organelle?
From free-living and extracellular to facultative intracellular, to obligate intracellular, to obligate intracellular mutualist, to organelle.
Where do enteric pathogens live?
In the gut