BIO 271L Midterm

What is Silvia’s email?

[e-mail]

Where do we go in the event of a tornado?

Stay in the room

Where do we go in the event of a fire?

Bartow

Which biosafety level are we?

1 but the room is set up for 2

What should you do when coming in to class?

Sign in, put up belongings, wash hands with soap, wipe down with amphyl

What is normal microbiota?

Microbes that are more or less permanent

What are transient microbiota?

microbes only present for days or weeks

Who discovered the importance of handwashing and how?

Ignaz Semmelweis

Medical students were going from autopsy rooms to delivering babies without washing hands and giving patients sepsis

What prevents the removal of all bacteria from skin?

oils

Will the skin ever be sterile?

no

What microscope do we use in class and what is it good for viewing?

Brightfield microscope; stained specimen

How do you calculate total magnification?

10 times the power of the objective lens

What objective lens do we do oil immersion on?

100x only

Why do we do oil imersion?

Oil keeps the light rays from refracting and has a low refraction rate compared to air. without it the image is dark

What medium were the first cultures done in?

broth; infusions and blood

What was the first solid medium Koch tried?

potato

What was the first liquid medium Koch tried and why didn’t it work?

gelatin, melted under standard incubation conditions

Who had the idea to use agar as a medium?

Angela Hess

What is chemically defined media?

a medium whose exact chemical composition is known

What is complex media?

media for which the chemical composition varies slightly from batch to batch

What are the properties of agar that make it so useful?

few microbes can degrade it

liquifies at 100 C

remains in liquid state till 40 C

once solidified, it can be incubated at temps up to 100 C and remain solid

What is most common method of sterilizing culture media?

Autoclaving

What are the autoclave numbers?

121 C, 15 psi, 15 minutes

What does it mean to inoculate a bacteria?

to intentionally introduce it to a medium

Why do we use aseptic techniques?

to exclude any contaminants

What is the advantage of broth cultures?

providing a large number of bacteria in a small space that are easily transported

What is the advantage of agar slants?

provide a solid growth surface and are easier to transport and store than plates

What is the advantage of the agar deep?

Viewing motility

What is the streak plate technique?

when a loop is used to streak the mixed sample several times over the surface of the solid medium in a petri plate

What is the spread plate technique?

a small amount of previously diluted specimen is spread over the surface of a solid medium using a spreading rod

What is the pour plate technique?

small amount of diluted sample is mixed with melted agar and poured into an empty Petri dish

How do you calculate cfu and what does it stand for?

Colony forming unit= # of colonies/ (dilution \* amount plated)

How do you calculate dilution?

amount transferred/ (amount transferred + amount already in tube)

How do you convert from mL to microliters?

1 mL= 1000 microliters

What temperature is a Bunsen burner?

1500 C

What is simple staining?

using one reagent to stain and all bacteria are stained similarly

What is differential staining?

using multiple reagents and bacteria react to the reagents differently

Why do we use structural stains?

to identify specific parts of microorganisms

What is a chromophore?

The ion that is colored during staining

What is the stain when a chromophore is a positive?

basic

What is a stain if the chromophore is a negative ion?

acidic

What is a direct stain?

a simple stain that stains the bacteria

What is a negative stain?

a simple stain that stains the background but leaves the bacteria unstained

What can simple stains be used to determine?

cell morphology, size, and arrangement

Why do we fix smears?

to kill the bacteria; coagulated proteins will cause cells to stick to the slide

What is the shape of cocci bacteria?

small and round

What is the shape of bacillus bacteria?

rod/pill shaped

Why do we use gram staining?

to identify and classify bacteria

What is the gram stain?

a differential stain that allows you to classify bacteria as gram positive or gram negative

How was gram staining discovered?

Hans Christian Gram found it when he attempted to stain cells and found that some lost color when excess stain was washed off

What is the first step of gram staining?

applying the primary stain which is crystal violet

What does the primary stain do?

it stains all bacteria purple

What is the second step in gram staining?

Applying the mordant which is iodine

What does the mordant do?

it combines with the crystal violet in the cell to form a crystal-violet iodine complex

What is the third step in gram staining?

applying the decolorizing agent which is ethyl alcohol or ethyl alcohol-acetone

What does the decolorizing agent do?

wash out the primary stain of some bacteria (decolorize it) while others are unaffected

What is the final step of gram staining?

applying the secondary/counterstain which is safranin

What does the secondary/counterstain do?

stains the decolorized bacteria red

What does the crystal violet-iodine complex do?

form a complex in the cytoplasm that binds to the cell wall

What happens to the CV-I in gram positive cells when the decolorizing agent is used?

it cannot be washed out

What happens to the CV-I in gram negative cells?

the decolorizing agent dissolves the outer lipopolysaccharide layer and the CV-I washes out through the thin layer of peptidoglycan

What cultures give the most consistent results when doing gram staining?

young cultures less than 24 hours old

What is a major limitation of dilution techniques?

organisms present in limited amounts may be diluted out on plates with more dominant bacteria

What is selective media?

media that prevents the growth of unwanted bacteria without inhibiting the growh of the desired organism

What is enrichment media?

usually liquid media that enhance the growth of desired bacteria

What is differential media?

media that contains various nutrients that allow the investigator to distinguish one bacterium from another by how they metabolize or change the media

What are enzymes?

Proteins that catalyze reactions

What are endoenzymes?

enzymes that function within the cell

What are exoenzymes?

enzymes released from the cell to catalyze reactions outside of the cell

What color will gram positive bacteria be under the microscope?

purple

What color will gram negative bacteria be under the microscope?

pink/red

What is catabolism?

chemical reactions that release energy from the decomposition of complex organic molecules

What are carbohydrates?

organic molecules that contain carbon, hydrogen, and oxygen in formula (CH2O)n

What are monosaccharides?

simple sugars containing 3-7 carbons

What are oligosaccharides?

composed of 2-20 monosaccharide molecules

What is the most common oligosaccharide?

disaccharides

What are polysaccharides?

composed of 8 or more monosaccharide molecules

What are hydrolytic enzymes?

enzymes that leave the cell and breakdown (by the addition of water) large substrates into smaller components

What does amylase do?

hydrolyzes starch

What is oxidative catabolism?

Catabolism that requires the presence of molecular oxygen

What is fermentative catabolism?

catabolism that does not require oxygen but can occur in its presence

What are the end products of fermentation?

small organic molecules, usually organic acids

What color does bromothymol blue turn in presence of acids?

yellow

What color does bromothymol blue turn in presence of bases?

dark blue

What are the subunits that make up proteins?

amino acids W

What elements are included in amino acids?

carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur

How do amino acids bond together?

peptide bonds

What color does phenol red turn in acidic conditions?

yellow

What color does phenol red turn in basic conditions?

fuchsia

What is deanimation?

removal of an amino group from an amino acid

What is decarboxylation?

removal of carbon dioxide from an amino acid

What color is bromocresol purple in acidic conditions?

yellow

What color is bromocresol purple in basic conditions?

purple

What color is phenol red in a uninoculated fermentation tube?

red

What does it mean when there is a clearing around the growth on a starch plate?

bacteria consumed starch, leaving nothing for iodine to bind to

What does it mean when there is not a clearing around the growth on a starch plate?

the bacteria could not consume the starch so it utilized the peptone instead

What is the respiration equation?

C6H12O6 + 6O2 → 6CO2 + 6H2O +38ATP

What color does methyl red turn in acidic conditions?

red

What color is methyl red in basic conditions?

yellow

What is a true fermenter?

one that produces gas and acid byproduct