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When you first bring pond water microbes to focus under the microscope, which objective should you use?
What is a differential Stain?
It's a stain that renders one type of microbe one color and other types of microbes another color.
Rinse with acetone. This dehydrates and tightens the cell wall of Gram + (peptidoglycan) so rinse does not enter cell and remains blue black because of the Crystal Violet - iodine complex. Gram - allows the rinse through its Lipid was calling for a counter stain - Safranin
Simple stains are + charged (cations). Most proteins are - charged (anions). Ionic attraction keeps the stain attached to the cells so rinsing w/ H2O does not remove color
Why cant you stain spores with Gram Stain?
Cell walls of most endospores are impermeable. You have to use steam to heat endospores and allow the Malachite Green to penetrate spore coat. Cells stain red and the spores stain green
Can you assume a clear area in a Gram stained slide is a spore?
No. could have been done incorrectly
1/10=0.1 (one tenth)
1/100=0.01 (one hundredths)
1/1,000=0.001 (one thousandths)
1/10,000=0.0001 (one ten thousandths)
1/100,000=0.00001 (one one hundred thousands)
1/1,000,000=0.000001 (one one millionths)
Is it possible that a colony could have arisen from two or more cells that stuck together?
It is possible that a colony could have arisen from two or more cells that stuck together. Thus a colony forming unit (CFU) may have originated from one or more cells.
How do you prove a pure culture?
by taking a sample from colony and re streaking on new plate. The new sample should be made up of the same microbe. You would have to proof by showing that all the colonies on restreak are identical and Gram staining these to demo all cells are identical
What temps do thermophiles prefer?
20degrees C to 45degrees C
optimal growth temp
If an organism can only grow in the presence of oxygen?
with or w/out oxygen
can tolerate oxygen?
Is a viable titer an underestimate or an overestimate of bacteria in soil sample? Why?
underestimate. you are only able to see visible and the count would have to be an underestimate.
Categories used to describe colony morphology.
Shape (circular, irregular.etc)
Margin (entire, unulated)
elevation (flat, raised, convex)
size (small, med, large,etc)
texture (smooth or rough)
Appearance (Glistening, dull)
Pigmentation (NON =cream,tan) (Pig = purple, red, yellow
What do you do if you can't measure the diameter of a zone of inhibition
measure the radius and multiply by 2
How do you know if a colony is alpha hemolytic?
Alpha hemolysis is a greenish discoloration that surrounds a bacterial colony growing on the agar. This type of hemolysis represents a partial decomposition of the hemoglobin of the red blood cells. Alpha hemolysis is characteristic of Streptococcus pneumonia and so can be used as a diagnostic feature in the identification of the bacterial strain.
How do you know if a colony is Beta hemolytic?
Beta hemolysis represents a complete breakdown of the hemoglobin of the red blood cells in the vicinity of a bacterial colony. There is a clearing of the agar around a colony. Beta hemolysis is characteristic of Streptococcus pyogenes and some strains ofStaphylococcus aureus.
What will happen in MSA if the bacteria produces acid
Thus only halophiles or
halotolerant bacteria can grow on this medium and it allows the differentiation of colonies that
can produce acids from mannitol because these will cause the medium surrounding the colony to
Why is MSA both selective and differential
Because it only allows for halophiles to grow there so it selects halophilic microbes and it will change color making it a differential. also it allows for differentiation of colonies that can produce acids from mannitol because these will cause the medium surrounding the colony to become yellow
steps to correctly streak an agar plate.
1. take an inoculating loop and flame it.
2. choose a colony from the agar plate with the colonies
3. dip the loop in the colony and get a sample
4. take the sample and streak 1/3 of a new agar plate
5. flame the loop again and let cool.
6. rotate plate 60 degrees and begin a new zig zag streak.
7. flame loop again and rotate again making the final streak from the last part of streak number 2
what bacteria should grow in lactose broth tubes?
e.coli coliforms. gass will be present in durham tubes in side the test tubes forcing the durham tube to rise.
You have a lactose broth tube with gas, one with out, and asparagine broth tube that glows. which should you inoculate on emb plate.
the lactose broth tube with gas because it shows signs of e.coli and emb plates are for the growth of e.coli you have a green sheen.
what happens to phenol red lactose broth if there is acid production?
there will be gas and change of color
how do we dislodge bacteria from hamburger?
put meat in blender with distilled water. this will dislodge bacteria from meat
what is brownian motion
brownian movements happens to any and all particles free in liquid environment. if there is no movement they may be attached to immobile object
How can brownian motion be distinguished from motility
Motility gets cells somewhere. In brownian movement the cells appear to just bounce around
what are the differences between procaryotic and eukaryotic flagella
eukaryotic flagella similar to cilia and possess many microtubules where as prokaryotic flagella is one microtubule
In wet mount preparations, is it possible to see eukaryotic flagella? prokaryotic flagella
Does crystal clear pond water contain living bacteria? What about air? Your finger
everything non sterile has bacteria
1. If your organisms were all blue, what is the Gram reaction?
If your organisms were all pink, what is the Gram reaction?
blue is gram+
pink is gram -
If your organisms were a mixture of blue and pink, what is the Gram reaction? Why? How
can that be proven?
gram +. if during prep some of the cells were damaged the stain would be allowed to leak out and thus giving you a false -
What are the functions of each ingredient in the medium
they provide sugars, amino acids, nucleotides, vitamins
What is the buffer in Nutrient Agar? Why do media have buffers
the buffers are amino acids. counter acts the acids or bases produced
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