Ch 10 Taxonomy and Classification Classification of Microbes
Taxonomy Science of Classification of organisms Hopes to show relationships among organisms Is a way to provide universal identification of an organism Why do we care things are related?
Q&A Pneumocystis jirovecii was thought to be a protozoan until DNA analysis showed it is a fungus. Why does it matter whether an organism is classified as a protozoan or a fungus?
Phylogeny or Systematics Shows evolutionary relationships and history among organisms Some obtained from fossil record Most bacteria use rRNA sequencing or some other sequence information A goal is to identify all organisms by 2025
Hierarchy Evolutionary relationships Species are groups that interbreed (have productive sex) How this goes Species Genus Family Order Class Division Phylum Kingdom (1969) Domain (80’s)
Scientific Nomenclature Binomial genus and specific epithet (species). Is used world wide Is always underlined Rules for naming are set by international committee’s –International Code of Zoological MomenclatureInternational Code of Zoological Momenclature –International Code of Botanical NomenclatureInternational Code of Botanical Nomenclature –Bacteriological Code and Bergey’s ManualBacteriological CodeBergey’s Manual
Scientific Binomial Source of Genus Name Source of Specific Epithet Klebsiella pneumoniae Honors Edwin Klebs The disease Pfiesteria piscicida Honors Lois Pfiester Disease in fish Salmonella typhimurium Honors Daniel Salmon Stupor (typh-) in mice (muri-) Streptococcus pyogenes Chains of cells (strepto-) Forms pus (pyo-) Penicillium chrysogenum Tuftlike (penicill-) Produces a yellow (chryso-) pigment Trypanosoma cruziCorkscrew-like (trypano-, borer; soma-, body) Honors Oswaldo Cruz Scientific Names
Species Definition Eukaryotic species: –A group of closely related organisms that breed among themselves Prokaryotic species: –A population of cells with similar characteristics –Clone: Population of cells derived from a single cell –Strain: Genetically different cells within a clone –Culture: grown in the lab Viral species: –Population of viruses with similar characteristics that occupies a particular ecological niche
Is it as easy to classify Microbes as it is Macrobes? How to classify What do we have to look at?
Figure 10.6 Phylogenetic Relationships of Prokaryotes
Of more than 2600 species identified so far Only about 250 or 10% are pathogens
Classification and Identification Classification: Placing organisms in groups of related species. Lists of characteristics of known organisms. Identification: Matching characteristics of an “unknown” organism to lists of known organisms. –Clinical lab identification
Bergey’s Manual of Systematic Bacteriology Morphological characteristics Presence of various enzymes Serological tests Phage typing Fatty acid profiles DNA finger printing Sequence of ribosomal RNA Is still very difficult
Identification Methods Morphological characteristic s : Useful for identifying eukaryotes Differential staining: Gram staining, acid- fast staining Biochemical tests: Determines presence of bacterial enzymes Figure 10.8 A dichotomous key
Figure 10.7 A clinical microbiology lab report form
Figure 10.8 Identifying a Gram – Negative, Oxidase – Negative Rod
Unknown enteri inoculated into tube After incubation the 15 tests are observed A numerical score is assigned The species is assigned This may be of is the strain has changed somehow. More tests are required
Design a rapid test for a Staphylococcus aureus. 10-14 Figure 6.10
Combine known antiserum + unknown bacterium Slide agglutination ELISA p288, 514 Western blot p289 Southern Blot p292 DNA chip p293 Serology study of serum and its immune responce Figure 10.10
Strains with different antigens are called –Serotypes –Serovars –biovars
Using Bergies manual Used to Identify bacteria not classify Features that are used to differentiate various organism often have little to do with arranging the orgs in taxonomic groups
4 major groups Domain Bacteria –Gram-negative Eubacteria that have cell walls. Proteobacteria –Non proteobacteria Gram negative bacteria –Gram positive Eubacteria that have cell walls Domain archaeobacteria