Lecture 3: Microbial Systematics Flashcards
Tuesday 8th October
What is sytematics?
The study of the diversity of organisms and their relationships
What Links phylogeny (evolutionary history) with taxonomy?
systematics
What should the genus/species name be written in?
Italics
What do the names of bacterial species reflect?
something about the organism
Describe how Staphylococcus epidermidis gets its name
-Staphylo= “bunch of grapes” clusters
- coccus= round-shaped bacterium
- epidermidis= isolated from skin
Describe how bacillus thermophilus gets its name
- Bacillus= rod-shaped bacterium
- thermophilus= grows at high temperature
is there a unified species concept in microbiology?
No
Why can’t a species in microbiology be defined in the same way as the general species definition?
- Because micoorganisms undergo asexual reproduction
- Because microorganisms undergo lateral gene transfer
- Phenotypic and genotypic plasticity of microorganisms
What is the current definition of a 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 does a polyphasic approach to classification in microbiology include?
- Phenotypic analysis: morphological, metabolic, physiological and chemical characteristics
- Genotypic: comparative at the gene and genome level
- Phylogenetic:framework of evolutionary relationships
How do you compare microorganisms using phenotypic traits?
- You look at the observable traits of the organism and compare with standard or type cultures.
What is the problem with looking at phenotypic traits when comparing micoorganisms?
a single mutation can change the apparent definition of a species
How can you look at the morphology of a cell?
- By gram staining, which allows you to look at cell shape, size and arrangement (single, chains, etc.), pleomorphism (existing in different shapes) formation of cysts, spores (shape, size, etc.)
- Looking at Presence of flagella, capsules, staining reactions, etc
How can you determine the motility of a microorganism?
by using phase-contrast microscopy
How can you test the nutrionality of a microorganism?
Testing for ability to grow on a range of compounds as sole sources of carbon, energy and nitrogen
Does gram staining help visualise bacteria/archaea ?
Yes
Does crytsal violet stain all cells?
Yes
What is a biochemical test that can be used to test the phenotypes of microorganisms?
- Look at how they decompose simple carbohydrates
- The microorganism is provided with glucose in a test medium. If the organism ferments glucose, it will produce acid (even in aerobic or anaerobic conditions).
- During fermentation, acids like lactate or acetate are produced, which lower the pH of the medium, leading to a color change in a pH indicator (commonly used is phenol red, which turns yellow in acidic conditions).
- CO2 collects in Durham tube. This provides additional evidence of fermentation
Can testing if a microorganism uses amylase to break down starch help identify a microorganism?
Yes
What are colony based characters?
Colony shape, margin, elevation, surface appearance, opacity, texture, pigmentation, odour and appearance of growth
What substances inhibit growth?
selective media, antibiotics, dyes, toxins, etc.
What pyhsiological properties can different bacteria have?
- Ability to grow in certain ph’s
- Ability to grow in high pressure environments i.e barophiles, which are organisms from the bottom of the ocean.
- Ability to grow in very salty conditions i.e halophiles
- Whether they’er aerobes, anaerobes. or microaerophile’s.
What are microaerophiles?
microorganisms that require low oxygen concentrations for growth
Which microorganisms work in low temperature environments of <15°C?
Psychrophiles
Which microorganisms work in normal temperature environments of 15-45°C?
Mesophiles
Which microorganisms work in high temperature environments of >50°C?
Thermophiles
Which microorganisms work in very high temperature environments of >80°C?
Hyperthermophiles
How are Psychrophiles adapted to live in low temperature environments?
Due to their protein structure and membrane fluidity, which prevents the membrane from getting too fluid
where do hypothermophiles live?
In hot springs and hydrothermal vents
Do we tend to use more molecular techniques to identify microorganisms?
Yes
How was the molecular identification of microbes done pre-sequencing?
- DNA-DNA hybridisation
- Fatty acid (FA) profiling
- DNA profiling
- Multilocus sequence typing (MLST)
