1. Samples of a microbial colony obtained from the natural environment are not pure culture. They are mixed cultures because the environment consists of an array of microorganisms and not one specific organism. A sample obtained from the natural environment such as water or soil may contain several species of microbes that need to be further isolated to obtain a pure culture.
2. Isolation streak plate technique involves the dilution of the sample several folds and then streaking a small amount using a sterile inoculation loop on an agar plate in a zig-zag manner. This is done to obtain a pure culture of bacteria from a mixed population by separating the microprocessor. When the sample is diluted into a small concentration and is streaked onto agar placed, widely spaced, discrete colonies of bacteria can be observed. These isolated colonies can be further cultured to obtain pure cultures by picking and re-streaking them on fresh agar plates.
3. A microbial colony is considered a pure culture because it consists of single species. A single species of bacteria cluster and form an isolated colony on an agar plate which can be further plated on fresh medium.
3-1 - If your agar plate shows discrete uncluttered colonies then you have obtained an isolated colony. The following picture might help you to understand.
3-2. If you subculture isolated microbes into a sterile nutrient broth without any contamination, it will still be considered pure culture because it is single isolated species in a sterile aseptic environment of the nutrient broth.
3.3. A pure culture can become a mixed culture due to contamination. This could be caused by airborne bacteria if your conditions are not aseptic. Contamination is possible if the work area is not clean and sterile or if the glassware is not sterile. The contamination can transform your pure culture into a mixed culture and is hence problematic. So, it is very important to maintain a sterile and aseptic environment, glassware, and instruments.
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The statement that is true about the population in <span>São Tomé and Príncipe is that it has the highest population but the lowest density in Central Africa. The correct answer is B. </span>
Answer: (A)
Dr. Pulaski is likely to find that approximately three-quarters (76 percent) of the subjects will conform to the group's judgment on at least one critical trial.
Explanation:
Solomon Asch conducted an experiment to find out to what extent people conform to group pressure.
He set up the experiment to include a single participant and seven confederates in a group. (A confederate is an accomplice of a researcher who is placed intentionally within an experiment by the researcher, so he can manipulate the experiment in his favor).
Each confederate was to give the same wrong answer to a certain question asked, while the participant was to provide his answer last.
Asch then observed if the single participant would tailor his answer according to the wrong answers provided by the confederates, or would provide the accurate answer.
Asch found out that from 12 trials conducted, "75% (three-quarters) of participants conformed to wrong answers provided at least once", while 25% did not conform at all.
He also discovered that on average of the trials carried out, one-third of the participants went along with the incorrect answer provided by the confederates.
Asch had also set up a control experiment with only a single participant and no confederates.
From the control experiment, he realized that less than 1% provided the wrong answer to the question asked.
