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.
How can you tell if a streak plate is contaminated?
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.
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 would you determine which colonies might be contaminants on a streak plate?
You could determine whether a colony on a streak plate or pour plate by carrying out a colony PCR . 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.
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.
What reasons might lead to absence of growth on a streak plate?
Streak Plate – should appear near or in a vaccinity of streak lines and sections. E9 – What factor(s) could accunt for an absence of growth on a pour plate? The lack of oxygen, poor/ bad bacteria smear, or difference in temperature that prevents optimal growth, within media .
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 can colonies be used to identify bacteria?
Colony morphology is a method that scientists use to describe the characteristics of an individual colony of bacteria growing on agar in a Petri dish. It can be used to help to identify them. A swab from a bin spread directly onto nutrient agar. Colonies differ in their shape, size, colour and texture.
Why does streaking for isolation result in separated colonies in the third and fourth quadrants?
As the original sample is diluted by streaking it over successive quadrants, the number of organisms decreases . Usually by the third or fourth quadrant only a few organisms are transferred on the inoculating loop and these produce a few isolated colonies.
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.
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.
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.
How might food utensils become contaminated?
During Food Preparation
Hands, utensils and equipment such as cutting boards can become contaminated with bacteria from raw food . If these things, once contaminated, are then used to prepare ready-to eat or cooked food, without first being thoroughly washed, food can become cross-contaminated.
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.
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 .
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 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 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 do you clean a streak plate?
There are a couple of things that you can do to clean the streak plates. For some of them, you can soak them in warm soapy water for a few minutes then use a kitchen sponge to scrub the surface . This works pretty well to remove the powder of some of the softer minerals.
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 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 streaking technique?
In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria . Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.
How do you inoculate bacteria into a nutrient agar plate?
Using a sterile pipette tip or toothpick , select a single colony from your LB agar plate. Drop the tip or toothpick into the liquid LB + antibiotic and swirl. Loosely cover the culture with sterile aluminum foil or a cap that is not air tight. Incubate bacterial culture at 37°C for 12-18 hr in a shaking incubator.
How can you tell if a plate is contaminated in agar?
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.
Why is bacteria not growing in petri dish?
Your bacteria may not be growing because if wasn’t placed in a warm or enriched environment . Hope this helps!
What might explain the presence of nontransformed bacteria growing on the LB amp plate?
Explain your prediction. Bacteria which resemble the non-transformed will be found on the LB/(-) pGLO plate. These bacteria were removed from the starter plate, did not have any plasmid added to them, and were replated on an LB plate. Thus, they are virtually identical to the non-transformed starter.
