Ch. 10 Classification of Microorganisms

The science of classifying organisms

Taxonomy

General name of an organism

Genus

Generally have several common characteristics that distinguish that species from all other species

Specific epithet

subgroup of a species with one or more characteristics that distinguish it from other subgroups of the same species

Strain

What characteristics of a eukaryote do we use to name the new organism?

Shape, mating ability

The study of the evolutionary history or organisms

Phylogeny

The 5 kingdoms:

Monera (all prokaryotes), protista, fungi, plantae, animalia 

From 2 different domains (bacteria & archaea). No nuclei or membrane-bound organelles

Kingdom Monera

Means first animal. Eukaryotes, mainly unicellular. Nutritionally and metabolically diverse.

Kingdom Protista

Eukaryotes. Chemoheterotrophs; aerobic or facultative anaerobes. Obtain nutrients solely by absorption of organic matter. May divide through mitosis or reproduce through formation asexual or sexual spores

Kingdom Fungi

Eukaryotes. photoautotrophs. Obtain nutrients by photosynthesis

Kingdom Plantae

Eukaryotes. chemoheterotrophs. Multicellular organisms. Some are parasitic and may be specialized to live in a host. Obtain nutrients by ingesting organic matter through some kind of mouth. 

Kingdom Animalia

Acellular infectious agents. Contain nucleic acid and protein coat. Not assigned a kingdom

Viruses

shape, arrangement. Presence of endospores, flagella

Morphological Characteristics

suffix for phylum

-ia

suffix for class

-ia

suffix for order

-iales

suffix for family

-aiceae

Suffix for genus

-ium

Microbes that enter the body stimulate it to form antibodies (“non-self”). Solutions of these antibodies are commercially available (“antisera”) and are used to identify medically-important microbes

Can differentiate between serotypes/serovars of same species. Help determine whether multiple outbreaks have a common origin

Serology

A type of serology test where you drop unknown bacteria on slide, add antiserum (solutions of antibodies)

–If bacteria clump (agglutinate), the test is positive (the antibody is binding to bacterial surface)

Slide agglutination test

Type of serology where known antibodies are attached to surface of microplate

Direct ELISA

Type of serology where known antigen attached to surface of microplate, add sample with possible antibody present (HIV test)

Indirect ELISA

Sensitivity of bacteria to different bacteriophages

bacterial viruses that are very specific to certain bacterial species/strains

Bacteriophages

For phage typing, if phage can infect bacteria, will see _________ (clearings in bacterial growth where cells were lysed)

Plaque

•Does not require culturing- can measure small numbers of bacteria!

•Fluid containing bacteria is forced through tiny opening (1 cell at a time)

•Laser beam detects scattered light

•Can stain cells or tag with fluorescent dyes, or add antibodies tagged with fluorescent dyes

•Potential for fast analysis of samples, because don’t need to culture!

Flow Cytometry

•Different species of bacteria will have different lipid contents

•Commercial machines to measure different fatty acids, often used in clinical and public health laboratories

Fatty Acid Profiles

•Mutations in rRNA genes happen very infrequently, but at a constant rate over time- frequency of mutations can act as a ____________ ________ → estimate time when two species diverged from a common ancestor

Molecular Clock

•Always same fixed ratio/percentage of Gs and Cs, same amount of As and Ts  

•Two related organisms should have similar percentages

•Used to categorize Gram-positive bacteria

DNA Base Composition (G+C content)

•Cut genomic DNA with restriction enzymes, should see similar pattern of cuts if similar species

•Used to identify bacteria species/serotypes during outbreaks

•Bands can be very large/differences can be very small… so, run on special gel

DNA Fingerprinting

•is a national network of public health and food regulatory agency laboratories that perform standardized molecular subtyping ("fingerprinting") of foodborne disease-causing bacteria.

PulseNet

•Maps that show evolutionary relationships

•Each branch point is a feature shared by all species on branch

Cladograms

–Successive questions with 2 possible answers

–Important for identification

Dichotomous keys