Metcalf Micro Lab Practical 2

thioglycollate and L-cystine are commonly used in microbiology to create anaerobic conditions in a culture medium by removing oxygen, allowing anaerobic bacteria to grow. The incorrect answers do not serve the same purpose and are not typically used for creating anaerobic environments.

Acinobacter is known to thrive in candle jars due to its unique growth requirements and compatibility with the environment created within the jar.

Clostridium is a genus of bacteria that is anaerobic, meaning it thrives in environments without oxygen such as a candle jar. On the other hand, Bacillus, Escherichia coli, and Streptococcus are aerobic bacteria that require oxygen to grow, therefore they would not survive in a candle jar.

Clostridium is known for its ability to thrive in anaerobic conditions, making it suitable for growth in a nutrient agar specifically designed for anaerobic bacteria. Escherichia, Staphylococcus, and Pseudomonas are not typically associated with anaerobic growth in this type of environment.

Acinobacter requires oxygen for growth, making it unable to grow in an anaerobic environment. Streptococcus is able to grow in both aerobic and anaerobic environments, Clostridium can only grow in the absence of oxygen, and Escherichia can grow in both aerobic and anaerobic conditions.

UV light is classified into three main types: UVA, UVB, and UVC. The wavelength of UV light typically ranges from 10 nm to 400 nm, with UVA having wavelengths of 315-400 nm, UVB having wavelengths of 280-315 nm, and UVC having wavelengths of 100-280 nm. UV light with a wavelength of 265 nm falls within the UVB range.

UV light causes changes in the DNA of bacteria, specifically by creating pyrimidine dimers which interfere with DNA replication and transcription, ultimately leading to cell death.

Food workers should wash their hands to prevent the spread of environmental bacteria which can lead to food contamination and foodborne illnesses. While washing hands may not completely remove normal flora, it is essential for food safety and overall public health.

Phages are viruses that infect and replicate within bacteria. Without the presence of growing bacteria, phages cannot continue to enlarge. Once the available bacteria reach a certain point in growth, the phage population stabilizes and does not increase further.

Coliform bacteria metabolize ONPG in Colilert broth as it contains this specific substrate for detecting the presence of coliforms.

In Colilert broth, ONPG is specifically metabolized by beta-galactosidase for the detection and enumeration of coliform bacteria.

The correct substrate that only E. coli metabolizes in Colilart broth is Mug, making it the correct answer.

Beta-glucoronidase is an enzyme that specifically metabolizes Mug in Colilert broth. The other options - water, sugar, and salt - are not metabolized by beta-glucoronidase in this context.

E. coli typically appears as red colonies with gas production on Petrifilm, while other coliforms appear as blue colonies with gas production. The color and gas production can help differentiate E. coli from other coliforms.

Lactose fermentation is the process where lactose is converted into gas and other byproducts by microorganisms like bacteria. This gas production leads to the formation of gas bubbles in the Petrifilm test.

In Colilert, a positive coliform test is indicated by a yellow color due to the presence of coliform bacteria metabolizing a specified indicator substrate.

In Colilert, a positive E. coli test is indicated by the presence of blue fluorescence under UV light.

Selective media are types of agar that encourage the growth of certain types of microorganisms while inhibiting the growth of others. Examples include Levine's EMB agar, MacConkey's agar, and Azide agar, which are commonly used in Lab 22 for specific purposes.

Levine's Eosin Methylene Blue (EMB) agar is a selective and differential culture medium primarily used for the isolation of Gram-negative bacteria, specifically inhibiting the growth of Gram-positive bacteria. Therefore, Gram-positive bacteria are inhibited from growing on Levine's EMB agar.

MacConkey's Agar is a selective and differential culture medium used for the isolation of Gram-negative bacteria. It inhibits the growth of Gram-positive bacteria such as Staphylococcus aureus and Candida albicans. Escherichia coli is actually a bacteria commonly associated with MacConkey's Agar.

MacConkey's Agar is selectively used to isolate and differentiate Gram-negative enteric bacteria such as Escherichia coli, while inhibiting the growth of Gram-positive bacteria and fungi.

Dark red colony indicates lactose fermentation, as certain bacteria will produce red color due to their ability to ferment lactose. This color change is a key indicator in microbiology for distinguishing different types of bacteria.

MacConkey's Agar is a selective and differential media used in microbiology to isolate Gram-negative bacteria. Pseudomonas is a common example of Gram-negative rod bacteria that can be identified on MacConkey's Agar due to its ability to ferment lactose.

In the test, dark centers for colonies actually indicate that it can ferment lactose, contrary to the common belief that it cannot.

MacConkey's Agar is a selective and differential media used to isolate and differentiate members of the Enterobacteriaceae family. Enterococcus is a Gram-positive, cocci-shaped bacteria that is Catalase negative, making it the correct answer for this question.

In the context of the test, a negative result indicates that there is no growth from Enterococcus and that Gram-positive bacteria are inhibited by crystal violet in MacConkey's agar. This specific reaction helps in identifying certain bacterial species.

The first sample being some coliform bacteria is indicated by the dark red color, while the second sample being a bile salt producer like E. coli is supported by the pink/white color due to the halo of bile salts in the medium.

The question is referring to the characteristic growth pattern of Enterococcus, a Gram-positive bacterium, on Azide and EMB media. Escherichia coli and Pseudomonas aeruginosa are Gram-negative bacteria while Staphylococcus aureus is a Gram-positive bacterium but does not display the specified growth pattern on the mentioned media.

Pseudomonas aeruginosa is a Gram-negative bacterium that is positive on Azide and EMB agar plates due to its characteristic growth and color reactions.