Lecture 3. Microbial Systematics Flashcards
What is systematics?
The study of the diversity of organisms and their relationships
Links phylogeny (evolutionary history) with taxonomy
What are genus/species names always written in?
Italics
What does “staphylo” mean in a bacteria’s name?
“Bunch of grapes” clusters
What does “coccus” mean in a bacteria’s name?
Coccus-shaped bacterium
What does “epidermis” mean in a bacteria’s name?
Isolated from skin
What does “bacillus” mean in a bacteria’s name?
Rod-shaped bacterium
What does “thermophilus” mean in a bacteria’s name?
Grows at high temperature
What is the current definition of species in higher organisms?
Interbreed and produce viable offspring
Why is the definition of species different in microbiology?
Asexual reproduction
Lateral gene transfer
Phenotypic and genotypic plasticity of microorganisms
What is the current definition of species in microbiology?
A group of strains that show a high degree of overall similarity and differ considerably from related strain groups with respect to many independent characteristics
What do phenotypic analyses analyse?
Observable traits of an organism (results are compared with standard or TYPE cultures)
What are the problems with phenotypic analyses?
A single mutation can change apparent definition of a species
Where do barophiles grow?
High pressure
Where do acidophiles grow?
pH <6
Where do alkaliphiles grow?
pH >8
Where do halophiles grow?
Very salty conditions
Where do microaerophiles grow?
Low oxygen concentration conditions
What temperature do psychrophiles grow at?
Low temperature (<15°C)
What temperature do mesophiles grow at?
Normal temperature (15-45°C)
What temperature do thermophiles grow at?
High temperature (>50°C)
What temperature do hyperthermophiles grow at?
Very high temperature (>80°C)
What is Fatty Acid Methyl Ester (FAME)?
Determination of fatty acid profile of membrane lipids
Growth under ‘standard’ conditions, extraction of lipids, chemically modify to methyl esters, analysis of FAME products by gas chromatography
Differences in chain length
Presence of double bonds, rings, branched chains or hydroxy groups
Compare chromatograms to database for best match
What are the drawbacks of FAME?
Fatty acid profile depends on growth conditions (temp,
medium, growth phase) which need to be standardised
Not all strains can be cultivated under those conditions
What is DNA-DNA hybridisation?
Genome wide comparison of sequence similarity
>70% = same species
>25% = same genus
What is fatty acid (FA) profiling?
Fame analysis
Pattern membrane Fas; depends on growth media, temp. and incubation time
What is DNA profiling?
Ribotyping, rep PCR, AFLP, etc.
Producing DNA fragment patterns for comparative analysis
What is multilocus sequence typing?
Characterising strains within a species
Sequence ‘housekeeping’ genes to assign different alleles to strains
What is amplified fragment length polymorphism (AFLP)?
PCR targeting repetitive elements in bacterial genome
Used to distinguish closely related strains
Analyses of results is comparison of electrophoretic patterns
