Aseptic Technique & Streaking
Leaving a culture tube open to the air, failing to flame the loop, or placing caps directly on the benchtop are common ways to introduce these.
What are contaminants?
These two basic bacterial cell shapes are spherical and rod-like, respectively.
What are cocci and bacilli?
This specialized liquid medium creates an oxygen gradient from top (aerobic) to bottom (anaerobic) to test aerotolerance.
What is Fluid Thioglycollate Medium (FTM)?
A positive catalase test is immediately identified by the vigorous production of this visible sign.
What are bubbles (oxygen gas)?
In gel electrophoresis, negatively charged DNA fragments migrate toward this positively charged electrode.
What is the anode (positive / red electrode)?
This is the primary goal of performing a 3-zone or 4-zone quadrant streak on an agar plate.
What is isolating pure / individual colonies (or CFUs)?
If you omit this step before simple staining, the bacteria will wash off the glass slide during the rinsing step.
If you omit this step before simple staining, the bacteria will wash off the glass slide during the rinsing step.
Organisms that only grow at the very top of an FTM tube where oxygen is abundant are termed this.
What are obligate (strict) aerobes?
The enzyme catalase breaks down toxic hydrogen peroxide 2H2O2 into these two harmless products.
What are water (H2O) and oxygen (O2)?
The three sequential steps that make up a single thermal cycle in a PCR run.
What are Denaturation, Annealing, and Extension (or Elongation)?
In a proper streak for isolation, this zone should show dense, confluent growth, while the final zone should exhibit well-separated, distinct colonies.
What is Zone 1 (or the first quadrant)?
Organisms lacking a membrane-bound nucleus are classified as this, while those with a true nucleus are eukaryotic.
What is prokaryotic?
Mannitol Salt Agar (MSA) inhibits most Gram-negative bacteria due to this high-concentration ingredient.
What is 7.5% Sodium Chloride (NaCl / Salt)?
Four standard macroscopic features used to describe bacterial colony morphology on an agar plate?
What are size, shape/form, margin (edge), elevation, color/pigmentation, or surface texture?
On an agarose gel, smaller DNA fragments travel this relative distance compared to larger fragments.
What is farther / faster (closer to the bottom)?
This crucial step must be performed between streaking each quadrant/zone to dilute the bacterial load across the plate.
What is flaming (sterilizing) and cooling the inoculating loop?
In a standard Gram stain, this chemical acts as a mordant to form a large complex with crystal violet.
What is Gram’s iodine?
When an organism ferments the carbohydrate mannitol on MSA, the phenol red pH indicator changes to this color.
What is yellow?
In dilution plating, only plates containing between this lower and upper range of colonies are considered countable and statistically reliable.
What is 30 to 300 colonies (CFUs)?
If a herpesvirus amplicon is 650 bp long, it will migrate to a position between these two bands on a standard DNA molecular ladder
What are the 500 bp and 750 bp bands?
A term describing a visible cluster of microorganisms originating from a single mother cell or group of identical cells on a solid medium.
What is a colony (or Colony Forming Unit / CFU)?
A student mistakenly applied Safranin first, then iodine, decolorizer, and finally Crystal Violet. All bacterial cells (regardless of Gram type) will end up appearing this color.
What is purple?
If a facultative anaerobe is placed into a completely sealed, oxygen-free tube, it can survive by switching from aerobic respiration to these catabolic processes.
What are fermentation and/or anaerobic respiration?
Calculate the original cell density: 65 colonies grew on a plate inoculated with 0.1 mL from a 10-4 dilution tube.
What is 6.5 X 106 cells/mL or (CFU/mL)?
[(65)/(0.1 x 10-4)] = (65/10-5) = 6.5 x 106)
These short, single-stranded sequences of nucleotides are engineered to bind specifically to flanking regions of a target gene (such as the herpesvirus glycoprotein gene) during PCR
What are DNA primers?