Unit 4 Flashcards
(32 cards)
Comparative Genomics
Using genomics to understand how organisms are related
Core genome
All of the genes shared by all of the strains of a species
Flexible genome
The genes that are not shared by all of the strains
Pan genome
All of the genes in the strains of a species
Endosymbiotic theory
Eukaryotic cells arose from the engulfment of prokaryotic cells by a larger cell - mitochondria and chloroplast
Evidence for the endosymbiotic theory
Both have outer and inner membranes, both contain ribosomes that resemble those of bacteria, both contain circular chromosomes
What is the last universal common ancestor
LUCA
Phylogeny
Evolutionary history of organisms - inferred based on genetic relatedness
Molecular clocks
Molecules that are used to measure the time of divergence of multiple organisms - molecules must have similar functions in all the organisms
Strain
Population of organisms that have descended from a single organism
The criteria in determining if two strains are the same in bacterial species:
- 16S rRNA sequence similarity: 16S rRNA sequences share 97%+ sequence similarity
- DNA hybridization: if >70% of their genomic sequences hybridize
- Average nucleotide identity: if their orthologous gene share 95%+ sequence similarity
Taxon
A set of microbes sharing a set of threshold similarity
When strains are found to define a new species, they must
- New name and characteristics must be published
- Strains must be saved in at least two culture collections
- A strain is designated as a Type Strain
Candidatus
If a new microbe discovered based on sequence data but no strains have been grown in pure culture
Microbial ecology
Microbes interact with other organisms and microbes interact with the environment
Population
Assemblages of similar organisms living in a common location
Communities
Assemblage of populations living in a common location - support a variety of relationships among the members
Symbioses
Interactions among organisms that involve a full range of positive and negative relationships
Commensalism
A relationship in which one organism benefits from the association while the other is neither harmed nor helped - most common relationship among organisms
Mutualism
Both partners gain from the association
Parasitism
One organism adversely affects the other
Obligate mutualist
Organism cannot survive separately - involves vertical transmission
Primary symbionts
Relationship is obligate for both partners (one host needs the other) - microbe is present in all hosts
Secondary symbionts
Relationship is obligate only for the microbe-microbe is only present in some hosts