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Taxonomy
The science that studies organisms in order to ARRANGE them into classes
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Identification
Process of characterizing in order to GROUP them
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Classification
Process of organizing organisms into SIMILAR groups
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Nomenclature
System for ASSIGNING names
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Explain why organisms are arranged in taxonomic groups.
This aids in UNDERSTANDING of relationships among species
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Give the order of taxonomic groups from the most general to the most specific.
- "Keep Pots Clean Or Family Gets Sick..."
- Domain, Kindgom, Phylum, Class, Order, Family, Genus, Species
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Domain
Collection of similar kingdoms. This is a new taxonomy category
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Genus
Group of similar related Species
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Species
Group of closely related isolates or strains – MOST basic group
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Strain
Most simple group, group of organisms of the same species with minor enough definitions to classify them as a separate VARIETY.
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How does MacConkey agar help to identify the cause of urinary tract infection?
It helps determine if there is bacteria in the urine. This test can determine if E. coli is present, for example, as it tests for Gram neg bac, and lactose fermenting vs. non-lac fermenting bacteria.
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Explain the basis of DNA hybridization and the kind of information it provides.
This helps to determine if 2 organisms are related. If single stranded DNA from each species hybridizes well enough together (ie: 70% hybridization = same species). If not, then they are not similar.
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Morphological studies –
size and shape can be determined, INITIAL step in determining (ie: bacilli – rod, cocci – sphere)
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Staining reactions
Gram + or – can be determined. Acid fast stain or Endospore stain can ID certain charateristics
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Biochemical reactions –
- most common way to ID species, and sometimes strains
- Most rely on pH indicators. These are more conclusive tests
- Can involve metabolic tests, such as Catalase, Citrate, Urease, MRVP. These detect things such as enzymes which, if present, aid in metabolism and therefore help ID the organism
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Serology
- strains can be differentiated.
- Help for RAPID detection of numerous organisms
- Relies on specific antigen-antibody reaction to help ID
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Phage typing –
- strains can be differentiated.
- ID’s organism by the PHAGE that infects it
- Certain strains of org. are susceptible to different bacteriophages (ie: viruses). When cells lyse you can determine if they are susceptible.
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Sequencing rRNA genes –
- there is little genetic variation in rRNA so helps determine org
- Amplify and sequence rRNA genes, do not need to grow in culture.
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Genomic typing –
molecular method of identifying RFLP’s
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DNA hybridization –
- Best to see relation on species level.
- Look at how 2 organisms’ single DNA strands hybridize to each other to determine nucleotide seq similarity.
- 70% hybridization = SAME SPECIES
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DNA base ratios
- determining the G-C basepairs in a genome offers a CRUDE comparison of genome
- If this ratio is deviated from 2 organisms, they are NOT related.
- This method does NOT determine relatedness however.
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Numerical taxonomy -
Groups taxonomical units based on their characteristics
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Identifying Bacteria Phenotypic characteristics
- Microscopic Morphology
- Metabolitic Capabilities
- Biochemical Tests
- Serology – relying on specific interaction between antigen and antibody.
- FAME (Fatty Acid Analysis) – cellular fatty acid comp is used as ID market and shown thru chromatography.
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Identifying Bacteria Genotypic characteristics
- Nucleic Acid PROBES – DNA probes used to locate specific nucleotide sequence of specific species & ID organism
- Amplifying DNA using PCR
- Sequencing of rRNA genes (amplifying then sequencing)
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