Practical Microm 302

UW

What is the size of protozoa?

20-100 micrometers

What is the size of yeast?

4-10 micrometers

What is the size of a bacteria?

1 micrometer

What is the size of a virus?

0.1 micrometers, too small to see with light microscope

What is the size of the pointer of the microscope at 10x?

25 micrometers

What is the size of the pointer of the microscope at 40x?

6 micrometers

What is the size of the pointer of the microscope at 100x?

2.5 micrometers

What will gram-positive look like under the microscope?

Purple

What will gram-negative look like under the microscope?

Pink

How many organisms are on a countable plate?

30-300

How can you use gelatin for a biochemical test?

Can inoculate by stabbing sample into tube and if the gelatin hydrolyzes, the sample contains “gelatinase”. This can be verified by bringing the gelatin sample to 4C

What will a tube with glucose salts + E. Coli look like?

Growth, turbidity

What will a tube with glucose salts + E. Coli + sulfa look like?

No growth since sulfa inhibits E. Coli growth

What will a tube with glucose salts + E. Coli +sulfa + PABA look like?

Growth since PABA outcompetes the sulfa drug

What will a tube with glucose salts + E. Coli + sulfa + TSY look like?

Growth since TSY has nutrients

What will an obligate aerobe look like in a tube?

Growth only at the top

What will a facultative anaerobe look like in a tube?

Growth throughout

What will an obligate anaerobe look like in a tube?

Growth only in the middle

Which is more heat resistant, E coli or Bacillus? At what temps do they die?

Bacillus is more resistant at 145-250C (spores), whereas E coli dies around 70-75C

What effect does UV have on growing organisms?

Kills cells by causing a lot of damage

What does Streptococcus Salivaus look like on a sucrose plate vs. without sucrose?

Like a gumdrop due to production of polysaccharide capsule with sucrose, little white growths without

What does Streptococcus Salivarus look like gram-stained?

Gram-pos cocci, long chains of cocci

When is the generation lime measured? WHich phase of metabolic activity?

Log phase when they are multiplying

What are the characteristics of Bacillus?

Gram-pos rods and is obligate aerobes or facultative anaerobe

What are the characteristics of Clostridium?

Gram-pos rod, obligate anaerobe

What are characteristics of Streptomyces?

Smell like earth called geosims, gram- positive rods, obligate aerobes. Look like hardened white powder with darker center

What will Bacillus endospore look like when stained vs. vegetative cells?

All green for endospores, pink for vegetative cells

What does susceptibility to an antibiotic look like?

No growth in area of antibiotic

What does resistance to an antibiotic look like?

Growth in antibiotic area

What are the characteristics of Acinetobacter?

Gram-neg, non motile rod, always naturally competent

What does it mean if something is prototrophic?

can grow on minimal media with one carbon source

What does it mean if something is an auxotroph?

Lacks ability to synthesize one or more essential metabolies

Will DNA grow on its own on TSY agar?

No

Will Trp+ grow on TSY agar?

Yes

Will Trp- grow on TSY agar?

Yes

Will Trp- grow on TSY agar with DNase?

Yes since DNase only harms naked DNA

Will DNA and Trp- grow on minimal media?

Yes

Will Trp+ grow on minimal media?

Yes

Will Trp- grow on minimal media?

No

Will DNA, DNase, Trp- grow on minimal media?

No since DNA is degraded, so nothing to incorprate

What are coliforms and what is an example of one?

Gram-neg rods that ferment lactose within 48 hours they produce gas and acid. E coli, Klebisella, Enterobacter

What is Lauryl lactose broth selective and differential for?

Gram-neg rods only, lactose fermenters

What is EMB agar selective and differential for and what do organisms look like on it?

Gram-neg rods, lactose fermenters turn pink (non = colorless), E coli look dark and green, Enterobacter just dark

What will Photobacterium look like when gram stained?

Gram neg rods

What will Vibrio look like when gram stained?

Gram neg straight/curved rods

During the epidemic lab, what organism was used to be spread and what are some characteristics?

Serratia marcenscens, gram-neg that produces antimicrobial called prodigosin that is orange/red

What will a virulent phage look like on an E coli lawn?

Clear plaque

What will a temperate phage look like on an E coli lawn?

Cloudy/opaque

What different types of Agrobacterium are there and how do they look?

Hairy root causes root growth, or cause tumors

What is MacConkey agar selective and differential for?

Lactose fermenters turn red/purple (non=colorless), gram neg rods

What is blood agar selective and differential for?

Differential for hemolysis.

What does a-hemolysis look like?

Partial breakdown so yellow/green/brown color on plate

What does B hemolysis look like?

Complete hemolysis so clear on plate

What are Gram-positive cocci?

Staphylococcus and enterococcus

What are some Gram-neg rods?

E coli, enterobacter, klebisiella, pseudonomas, proteus

What are some lactose positive organisms?

E coli, enterobacter, klebisiella

What are some lactose negative organisms?

Pseudonomas, proteus

What is the catalase test?

Tests for enzyme catalase that breaks down H2O2 to H2O and O2. Positive test is bubbles and indicates catalase present and Staphylococcus. Catalase negative indicates Enterococcus

What is the lactose ferment test?

Tests organism’s ability to ferment lactose and a positive test is indicated by a pH change, from gold to pink, along with gas present in the Durham vial. Results can be NC, A, AG. A positive result indicates E coli, Enterobacter, or Klebsiella. Negative is Pseudonoma, Proteus

What is the Indole test?

Checks if tryptophanase is present with catalyzes tryptophan. Kovac’s reagent is added to a tube of broth + organism. A positive result is shown as bright red/pink top layer, like E. Coli

What does Methyl Red (MR) test indicate?

MR is a pH indicator from glucose fermentation using mixed acid fermentation pathway and is red at pH <4.4, yellow at pH >6.2. Red color is positive like for E. Coli since it used mixed acid fermentation pathway and enterobacter and klebsiella are negative since they use butandiol pathway.

What does the Voges-Prokauer (VP) test show?

Also known as acetoin test, checks for acetoin which is made by butandiol pathway users like klebsiella or enterobacter, not E coli. A positive result is a gradual red color appearing at the top of the solution and darkening over time

What is the Citrate test?

Tests if organism can use citrate only to grow and has a pH indicator that is green at neutral/acid pH, blue at basic pH. Growth is positive along with sometimes blue pH indicator like for enterobacter and klebsiella. No growth is a negative result

What is the motility test?

Agar with a redox-sensitive dye that becomes red from colorless when reduced. It is positive with a haze of pink growth from the stab like for enterobacter, or just a red stab is klebsiella

What does the oxidase test show?

identifies cytochrome c oxidase enzyme that is the terminal oxidase in the ETC for aerobic respirers. Read immediately, bright pink where sample is is positive result like for Pseudonomas, and dark purple for negative like Proteus

What will glucose ferment test tell us?

Tests organism’s ability to ferment glucose and a positive test is indicated by a pH change, from gold to pink, along with gas present in the Durham vial. Results can be NC, A, AG. A positive result indicates Proteus. Negative is Pseudonoma

What are the mmicrobiota of the throat and what are their hemolytic ability/characteristics?

Streptococcus (a catalase negative), S, pyogenes (b), Neisseria (non-hemolytic, kidney dicocci shaped), lactobacillus/Corynebacterium (gram-pos rods), Candida (yeast),

What is Immunoprecipitation?

When bound antibody to antigen creates insoluble precipitate. No precipitate = no recognition. Positive result only signifies presence of something, not absence of something else

What are mannitol salt agar plates differential and selective for?

Pink plate that selects for Salt-tolerant organisms and mannitol fermenters turn from pink to yellow, so for staphylococcus

What are the characteristics of S. aureus?

Mannitol fermenter, golden colonies, gram positive cocci

What are the characteristics of S. epidermidis?

Small shiny white colonies that are not mannitol fermenters, gram pos cocci

What is the Kirby disc diffusion assay?

Suspension of organisms is made across an agar plate as a lawn and antibiotics placed on top. This diffuses into the agar and makes zones of inhibition if susceptible

What is Muller-Hinton agar?

Rich medium

What counts as the zone of inhibition?

Not a single colony present within it

What can affect the zone of inhibition?

Concentration of antibiotic, organism’s sensitivity, molecular weight of the antibiotic