Micro

Counting colonies on a plate

Direct and viable

Counting colonies using spectrophotometer

Indirect and total

As transmittance increases, turbidity:

Decreases

If you take 1ml of a culture and add it to 9 ml of media, what kind of dilution is this?

1:10

Would you use a plate with 500 colonies or one with 120 colonies to determine the
concentration of bacteria in your original culture?

The one with 120 colonies

If your organism grew throughout a thioglycollate tube but benefited from oxygen, how would you classify it?

Facultative anaerobe

If an organism grows at low oxygen, what is it called?

Microaerophile

How would you classify an organism that grows optimally at 37 degrees C?

Mesophile

What is the optimal growth for Serratia marcescens and how
would you classify this organism?

25 degrees C, psychrotroph

What color are the colonies of Serratia marcessans at 25 degrees C?

Red or pink

An extreme or obligate halophile grows at what salt concentration?

15%

Organisms that can grow at salt concentrations up to 10% are called ____________.

Facultative halophiles

Why are Bacillus most resistant to heat than other organisms?

They have endospores

What is to the time to kill all cells in a culture at a given temperature?

Thermal death time

What is the time, in minutes, to kill 90% of a population at a given temperature?

Decimal reduction time

What does UV irradiation do to the DNA?

It creates thymine dimers

Is UV radiation ionizing or nonionizing?

Nonionizing

For the UV experiment, the side of the plate covered with the index card, had more or less colonies?

More

When you place an antibiotic disc on a bacterial plate, do you measure the radius or diameter of the zone of inhibition the next day?

Diameter

What are some reasons for antibiotic resistance?

Using antibiotics too often or when not needed
Plasmids with antibiotic resistance genes
Bacteria can pump out antibiotics

Is the m-Staph broth, selective, differential or both?

Selective

Are the MSA plates selective, differential or both?

Both

SHOULD Novobiocin be sensitive towards
Staphlocococcus aureus, Staphylococcus epidermidis or both?

Both

How does Staphyloslide work?

The antibodies in Staphyloslide bind to the antigens on Staph. aureus

Which organism(s) tests positive for coagulase?

Staphylococcus aureus

Bacterial enumeration

The measurement of the number of bacterial cells per milliliter, gram, or cubic meter of a sample (the units depend on the nature of the sample)

Direct Counts

...means actually counting cells
More accurate, but takes a lot longer

Indirect Counts

mean estimating the number of cells based on turbidity in liquid or dry weight.
Less accurate, but quick

Total count

All the cells in a culture

Viable count

Only live cells in a culture

obligate anaerobes

Cannot tolerate oxygen

Obligate aerobes

Require oxygen

Facultative anaerobes

Can grow with ot without oxygen

Microaerophiles

Grow at low concentrations of oxygen

Aerotolerant

Cannot use oxygen, but tolerate it well

Oxygen test uses semi-solid media called thioglycollate broth.

there is a pink indicator to demonstrate
that oxygen is present in the broth. When oxygen is used, it will disappear.

If an organism can only grow on the 1% or 5% salt plates only, it is
classified as

Non-halophile

If the organism can also grow on the 10% plate, it is
classified as

a Facultative halophile

If it can grow on the 15% salt plates, it
is called

an Extreme halophile

Hypotonic

Less salt in the environment and more inside the cell (cell will lyse)

Hypertonic

More salt in the environment and less inside the cell (cell will shrink)

Isotonic

Equal level of salt in the environment and inside the cell

Osmosis

How the water moves into the cell...by osmosis

Psychotrophile

Temp range -10 to 20 degrees C (Optimal growth 10 degrees C)

Psychotroph

Temp range 5 to 30 degrees C (Optimal growth 25 degrees C)

Mesophile

Temp range 10 to 45 degrees C (Optimal growth 37 degrees C)

Thermophile

Temp range 40 to 75 degrees C (Optimal growth 55 degrees C)

Hyperthermophile

Temp range 65 to 120 degrees C (Optimal growth 90-100 degrees C)

++ double-positive

Lots of growth

+ positive

Some growth

- negative

No growth

Broths that produced a pinkish color in temp lab meant that ______________.

it grew very well. (The darker the pink, the better the growth).

Indole test

Performed to help differentiate species of Enterobacteriaceae. Tests bacteria's ability to produce indole.

Indole Media and reagents

Tryptone broth (contains tryptophan). Kovac's reagent-HCL, dimethylamoniobenzaldehyde, and amyl alcohol.

Indole results

Positive- Kovac's reagent reacts to indole and creates a red color at the top part of the test tube. Negative remains yellow.

Methyl Red/ Voges Proskauer (MR/VP)

Both tests Performed to help differentiate species of Enterobacteriaceae

MR

Tests for endproducts from glucose fermentation

VP

Tests for acetoin production from glucose fermenation

MR/ VP Media and reagents

Glucose broth. Methyl Red indicator for acid. Voges Proskauer reagents: 5% Alpha-Napthol and ethanol; Potassium Hydroxide and Deionized water.

MR result

Positive result is red (indicating a pH below 6); Negative result is yellow (indicating no acid production)

VR result

Positive result is red after VP reagents added (Indicating presence of acetoin); Negative result has no color change.

Citrate

Performed To help differentiate species of Enterobacteriaceae. Selective for bacteria that consumes citrate as its sole source of carbon, and ammonium as its nitrogen source.

Citrate Media and reagents

Simmon's citrate Agar (sodium citrate as carbon source), ammonium ion (as nitrogen source), ans pH indicator-bromthymol blue.

Citrate result

Positive-Blue color-( indicates bacteria metabolized citrate and produced acid as an end product). Negative result- Green.

H2s Production in SIM

Used to differentiate species of the family Enterobacteriaceae. Determines bacteria's ability to reduce sulfer into H2S.

H2S in SIM Media and reagents

SIM media-contains sulfer, cysteine, sodium thiosulofate, and peptonized iron or ferrous sulfate.

H2S in SIM results

Positive result-contents of tube turn black; Negative results- Does not turn black.

Urea Hydrolysis

Done to determine a bacteria's ability to hydrolyze urea to make ammonia using enzyme urease.

Urea Media and Reagents used

Urea broth (Yeast extract, monopotasium phosphate, disodium phosphate, urea) Phenol red indicator.

Urea results

Positive: Bright pink-indicates ammonia is made. Negative: Yellow (no color change)

Motility test

Performed to help differentiate species of bacteria that are motile.

Motility Media and Reagents

Motility media contains tryptose, sodium cholride, agar, and a color indicator.

Motility results

Positive: Red line will be growth going out from the stab line. Negative: red color will be straight down.

Lactose fermentation

Tests ability of a bacteria to ferment lactose

Lactose Media and reagents

Lactose broth: Beef broth, geletin peptone, and lactose. Phenol red indicator added to indicate acid production from fermentation.

Lactose results

Positive: Yellow after indicator is added; Negative: Reddish, no color change

Sucrose Fermentation

Tests ability to ferment sucrose and production of acid end product

Sucrose Media and reagents

Sucrose broth: Beef broth extract, gelatin peptone, and sucrose. Phenol red indicator detects acid end-product.

Sucrose results

Positive: Yellow; Negative: No color change or reddish.

Glucose Fermentation and Gass Production

Tests bacteria's ability to ferment glucose and produce gas and/or acid end product

Glucose Media and reagents

Glucose broth: Beef extract, gelatin peptone, and glucose. Phenol red indicator to indictae acid end product. Durham Gas tube added to indicate gas production.

Glucose results

Positive: Yellow indicating presence of acid and glucose fermentation; Positive result for gas is a bubble in Durham's tube; Negative: No color change, or reddish color and no bubble.

BAP with Novobiocin Test

Determines if organism is resistant or sensitive to novobiocin, and determines if organism can lyse red blood cells.

BAP Media and reagents

Nutrient agar w/ 5% sheep's blood. Novobiocin disk added after inoculation.

BAP results

Positive: Hemolysis- Occurs if media surrounding colonies turns translucent or green in color.

MSA (Manitol Salt Agar)

Tests bacteria's ability to tolerate 7% salt concentration and ferment mannitol. Selective--selects for salt tolerant bacteria. Differential---because it differentiates salt tolerant organisms on their ability to ferment mannitol.

MSA Media and reagents

MSA media--nutrient agar, mannitol, 7% sodium chloride and phenol red indicator.

MSA results

Can ferment mannitol: yellow zones around the colonies. Cannot ferment mannitol: Media will remain pink. Organism will grow if it can tolerate salt. Will not grow if it can't.

Mstaph Broth

Tests bacteria's ability to tolerate 7% salt concentration and ferment mannitol. Selective, because it selects salt tolerant Staphlyococcus.

Mstaph Broth Media and Reagents

Contains nutrients appropriate for growing Staphylococcus and 7% salt.

Mstaph results

Positive: Cloudy, will grow--tolerates salt; Negative: Clear (yellow), will not grow--does not tolerate salt.

Coagulase

Tests for bacteria's ability to clot blood plasma using enzyme coagulase.

Coagulase Media and reagents

Rabbit plasma dissolved in buffer.

Coagulase results

Positive: Clumps Negative: No clumps

Zone of inhabition

Measured in mm. I dentify S (Sensitive), I (Intermediate), or R (Resistant).