Checking for Contamination
Look for
signs of fungal contamination
. Fungal contamination will appear as fuzzy, filamentous, or hair-like growths, and should be visible to the unaided eye. Fungal contamination often occurs right along the edge of an agar plate.
How can a streak plate become contaminated?
How can a streak plate become contaminated?
If the loop is not sterilized
. If you drop the plate. If lid isn’t on.
How is contamination avoided when streaking plates?
Avoid the edge
.
Contact with the edge of the plate can introduce contaminates to the agar. Avoid touching the edge of the plate with the loop while streaking or inoculating the agar with the swab.
What could be a possible explanation for what went wrong on the streak plate below?
Obtaining a culture sample before streaking every quadrant. … What could be a possible explanation for what went wrong on the streak plate above?
The quadrants are not properly spaced & The loop was not sterilized between quadrants
.
When using the streak plate technique
how often is it necessary to sterilize your loop?
What reason could there be for failing to obtain isolated colonies on a streak plate?
The culture plate has colonies that do not look like most of the colonies, or there are colonies where nothing was streaked. Reason:
The plate has become contaminated with bacteria or fungi from the environment
.
What is a contaminated culture?
A
culture in which bacteria from a foreign source have infiltrated the growth medium
.
What does the word contaminant mean?
English Language Learners Definition of contaminant
:
something that makes a place or a substance
(such as water, air, or food) no longer suitable for use : something that contaminates a place or substance. See the full definition for contaminant in the English Language Learners Dictionary.
What makes a streak plate successful?
Tips for the best results: Use only a small amount of inoculum.
Streak lightly so that you do not gouge the agar
. Flame the loop after you streak each quadrant.
How do bacteria spread on agar plates?
Sterilize a plate spreader and touch it to the surface of the agar, away from the dispensed liquid, to cool. To spread the dispensed liquid around the plate,
gently push the plate spreader back and forth
. Use your other hand to hold the lid above the plate and to spin the plate to get an even spread.
How can we prevent agar plate contamination?
- Clear the work space of all non-essential items.
- Clean the desk with disinfectant. Reason – this kills all unwanted bacteria and so decreases the chance of the agar plate becoming contaminated.
What is the purpose of streak plating in this lab?
Streak plate technique is
used to grow bacteria on a growth media surface so that individual bacterial colonies are isolated and sampled
. Samples can then be taken from the resulting isolated colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.
How would you determine whether a colony was a contaminant?
A colony PCR is an experiment whereby a specific DNA sequence is amplified by a heat stable DNA polymerase enzyme. The DNA which is amplified is specified by oligonucleotides called primers.
If the colony does not amplify using primers specific for the desired microbe
it means that the colony is a contaminant.
What are the advantages and disadvantages of streak plate method?
Disadvantages. The streak plate method
does not work with high volumes of organisms
. It will not enable you to get a concentration count. It requires huge storage space and there is a possibility that your incubator cannot accommodate a large volume of petri plate.
How could your streak plate technique be improved?
How could your streak plate method be improved? Because the purpose of a streak plate is to obtain isolated cultures from an inoculum,
consider using a fourth quadrant to further increase the probability of isolated cultures
.
How can a culture become contaminated?
Unintentional use of nonsterile supplies, media, or solutions
during routine cell culture procedures is the major source of microbial spread. Contamination is a prevalent issue in the culturing of cells, and it is essential that any risks are managed effectively so that experiment integrity is maintained.
How can contamination occur?
Contamination may occur from
preparing food on a surface that still has chemical residue on
it or if someone sprays cleaning chemicals close to uncovered food. Additionally, food can become contaminated from chemicals before it even reaches the kitchen.
How do you identify contamination?
- Infected cultures usually appear cloudy (i.e., turbid), sometimes with a thin film on the surface.
- Sudden drops in the pH of the culture medium is also frequently encountered.
What are examples of contaminants?
Examples of chemical contaminants include
nitrogen, bleach, salts, pesticides, metals, toxins produced by bacteria, and human or animal drugs
. Biological contaminants are organisms in water.
Which substance that causes contamination?
Some of the most common causes of chemical contamination are
cleaning products or pesticides and herbicides
from unwashed fruit and vegetables. Examples of chemical contaminants are: industrial chemicals. agricultural chemicals.
What is contamination in biology?
Definition.
The presence in the environment of living organisms or agents derived by viruses, bacteria, fungi, and mammal and bird antigens
that can cause many health effects.
How do you know if the streak plate method was performed correctly?
If you streaked correctly, you
will see isolated colonies in the third sector
. The heaviest growth will be in the first sector. There will be less growth and some isolated colonies in the second sector. The third area should have the least growth with isolated colonies.
Why is it necessary to sterilize the loop between streaking?
When an agar plate is streaked for isolation, why is the loop sterilized in between each section of the plate? The loop is
sterilized to reduce the number of bacteria being streaked on the plate
. Only those bacteria originally placed on the plate can be transferred to the next section.
How does a bacterial colony appear?
A bacterial colony is what you call a group of bacteria derived from
the same mother cell
. This means that a single mother cell reproduces to make a group of genetically identical cells, and this group of cells form a mass, which is known as a bacterial colony.
What is spreading and streaking?
The key difference between streak plate and spread plate is that the
streak plate is used to isolate and purify a particular bacterial species from a mixture of bacteria
while the spread plate is used to enumerate and quantify bacteria in a sample.
What is the principle of spread plate method?
The main principle behind this Spread Plate technique is that
as the Petri dish rotated, at some stage, single cells will be deposited with the bent glass rod on to the agar surface
, these cells will be separated from each other by a distance sufficient to allow the colonies that develop to be free from each other.
How can we prevent contamination in the laboratory?
- Sterilize your equipment. The most common preventative measures against contamination in the lab is sterilization. …
- Check the quality of your water and air. …
- Consider antibiotics. …
- Organize your lab. …
- Use common sense measures.
How does a streak plate differ from a pour plate?
The main difference between streak plate and pour plate is that in streak plate,
the first to be added is the melted nutrient agar and the second to be added is a loop of bacteria from a slant
, whereas the first to be added in pour plate is the bacterial broth and the second to be added is the nutrient agar.
What is the purpose of re streaking your environmental unknown?
As you might guess, the purpose of streaking for isolation is
to produce isolated colonies of an organism on an agar plate
. This is useful when you need to separate organisms in a mixed culture or when you need to study the colony morphology of an organism.
What is a streak plate?
Streak Plate. A
common method for the isolation of a pure culture from a mixture
is by “streaking” plates. The inoculum is streaked over the agar surface to isolate colonies on at least a portion of the plate.
How can you prevent contamination of the agar with air borne bacteria?
Agar plates should be opened facing away from the user, and preferably only just enough to complete the work
. This prevents contamination of the agar plate by microorganisms present in the air, fungal spores in particular.
What methods can be used to control microbial contaminants in the laboratory?
- Physical control includes such methods of control as high or low temperature, desiccation, osmotic pressure, radiation, and filtration.
- Chemical control refers to the use of disinfectants, antiseptics, antibiotics, and chemotherapeutic antimicrobial chemicals.
How would you know if the streak plate is contaminated?
Fungal contamination will appear as fuzzy, filamentous, or hair-like growths, and should be visible to the unaided eye. Fungal contamination often occurs right along the edge of an agar plate. … If the plate has not been inoculated,
the presence of any bacterial colonies
indicates contamination.
What could be a possible explanation for what went wrong on the streak plate below?
Obtaining a culture sample before streaking every quadrant. … What could be a possible explanation for what went wrong on the streak plate above?
The quadrants are not properly spaced & The loop was not sterilized between quadrants
.
When using the streak plate technique
how often is it necessary to sterilize your loop?
What would happen if you touched quadrant one while streaking quadrant four?
It gives better isolation of colonies. It is quick and takes less materials. What would happen if you touched quadrant one while streaking quadrant four? …
You would spread a lot of bacteria from quadrant one into quadrant four and probably not see isolated colonies
.
How do you determine whether a colony is a contaminant or a real bacterial culture?
1.
Perform Gram staining and look at the morphology of the bacterial cells
, if contaminated more than one cell type shall be visible. 2. Streak the culture on a suitable agar based medium and observe color and type of cfus.
What is a contaminant in microbiology?
Microbiological contamination refers to
the non-intended or accidental introduction of infectious material like bacteria, yeast, mould, fungi, virus, prions, protozoa or their toxins and by-products
.
Can some bacteria grow on the streak plate?
After incubation, bacterial growth is visible as colonies in and on the agar of a pour plate. … Can some bacteria grow on the streak plate and not be seen if the pour plate technique is used? Yes, the pour plate is O2 limited. Thus,
some bacteria will only grow on the streak plate as it provides ample O2
.
