BIOL 2401 Week 6 Unit 4: Characteristics of Microbes

Coccus

Bacillus

Coccobacillus

Vibrio

Spirillum

Spirochete

Diplococcus

Tetrad

Streptococcus

Staphylococcus

Streptobacillus

Peritrichous

Monotrichous and polar

Lophotrichous and polar

Amphitrichous and polar

Purpose of crystal violet

Stains cells purple or blue

Purpose of iodine (mordant)

Helps dye adhere to cell walls

Purpose of decolorizer

Washes away stain from gram-negative cell walls

Purpose of safranin

Counterstain which allows dye adherance to gram-negative cells, making gram-negative cells appear pink or red

Obligate aerobe oxygen-free bacterial growth

Obligate anaerobe oxygen-free bacterial growth

Facultative anaerobe oxygen-free bacterial growth

Aerotolerant anaerobe oxygen-free bacterial growth

Microaerophiles

Phenol red pH range

• Neutral pH → red color

• Acidic pH → yellow color

Inverted tube

Used to detect formation of gas, such as CO₂

Gelatinase test

Tests whether an organism can digest gelatin (protein)

• Bacterial culture + gelatin

How do protease-positive bacteria liquefy gelatinous mediums?

Through digestion of the medium with extracellular proteases

Deamination test

Tests whether an organism can digest amino acids

• Bacterial culture + phenol red + amino acids

Urease test

Tests whether an organism can digest urea

• Bacterial culture + phenol red + urea

What percentage of test results in the Bergey’s manual must match for the positive ID of a species?

100% of test results must match!

Serological tests

Uses antibodies to help identify specific strains and species of bacteria

Positive serological test

Antibody-antigen binding → indicates presence of specific bacteria

Negative serological test

No antibody-antigen binding → indicates absence of specific bacteria

Serotype

Distinct strain, with different antigens

Slide agglutination test

Uses latex beads to either detect specific antibodies or antigens

If latex beads are coated with antigens, it will detect ________________

specific antibodies

If latex beads are coated with antibodies, it will detect ________________

specific antigens

Direct ELISA (Enzyme-Linked Immunosorbent Assay)

Detects antigen in sample with a known antibody. Used to detect drugs or hormones in urine

Indirect ELISA (Enzyme-Linked Immunosorbent Assay)

Detects antibody in sample with a known antigen. Used to detect antibodies in patient serum

ELISA (Enzyme-Linked Immunosorbent Assay)

Serology using specific antibodies to detect presence or exposure to a pathogen

DNA sequencing

Determines full genome of species. Most accurate way of determining species