Bio246-lab-quiz#3 (part 1)

Bacterial growth and an increase in bacterial cell size are distinct concepts in microbiology, where the former refers to the overall increase in the number of bacteria, while the latter focuses on the enlargement of individual bacterial cells.

Streaking for isolation involves the gradual dilution and separation of bacteria colonies, which ultimately results in the formation of pure colonies. Mixing different bacteria, causing faster multiplication, or altering nutrient content does not contribute to obtaining pure colonies through streaking.

Streaking for isolation involves a specific pattern across the dish to ensure the bacteria are separated and isolated properly. Streaking in a random pattern, focusing on only one quadrant, or not sterilizing the loop between streaks can lead to contamination and inaccurate results.

The correct answer is Quadrant O and I because they receive the initial streak of inoculum and in subsequent quadrants, the bacteria get diluted resulting in less growth.

Quadrants II and III are used for streaking because they contain the least amount of bacteria. This allows for individual colonies to form without interference from neighboring bacteria.

Streaking for isolation is a technique used in microbiology to obtain isolated colonies of bacteria on an agar plate. It involves spreading bacteria across the surface of the agar in a petri dish in a way that allows individual bacterial cells to grow into visible colonies that can be separated from one another.

Cell division typically takes around 20 minutes for 2 daughter cells to form from 1 mother cell. This process continues, leading to exponential growth as more daughter cells are produced over time.

A pure culture is defined as a culture containing only one type of bacteria, ensuring that there is no contamination or presence of other microorganisms.

Confluent growth refers to a dense and continuous layer of bacterial growth resembling a lawn.

CFU stands for Colony Forming Unit, which is a measure of viable bacterial or fungal cells capable of forming a colony. It represents the number of cells or microorganisms in a sample that are capable of reproducing and forming colonies under specific conditions.

The correct answer lists the specific bacteria used in the streaking module, which are Escherichia coli, Serratia marcescens, and a mixed sample. The incorrect answers provide different combinations of bacteria that were not used in the streaking module.

Pasteurization is a process used to kill harmful bacteria and pathogens in food products, increasing their safety and extending their shelf life. It does not add flavor or nutrients, reduce production costs, or speed up ripening.

The FDA guidelines for milk safety involve accepting a certain amount of bacteria due to their non-pathogenic nature, and specific temperature and time recommendations for ensuring safety.

Raw milk can contain various harmful pathogens like Campylobacter jejuni, Listeria monocytogenes, Staphylococus aureus, Escherichia coli, Salmonella sp., and Yersinia enterocolitia, but not Clostridium botulinum, Aspergillus fumigatus, or Cryptosporidium parvum which are not commonly found in raw milk.

Milk can become contaminated when it comes into contact with sick cows, contaminated milking supplies, or the individuals handling the milk. Improper refrigeration can also lead to increased growth of bacteria.

Serial dilutions involve a sequential process of diluting a solution to reduce the concentration of bacteria present in the sample. This technique is commonly used in scientific experiments to obtain samples with lower and known concentrations for various analyses.

When calculating dilutions, the correct formula is to divide the total volume by the sample volume to obtain the dilution ratio.

To calculate the numbers of bacteria in a mL of sample, you need to use the formula provided in the correct answer which involves multiplying the number of isolated bacteria by the dilution factor.

Equivalent treatments in pasteurization imply that adjustments in temperature can compensate for changes in time required to achieve the desired outcome, ensuring the same level of treatment effectiveness.

Coliform or enteric bacteria are the specific type of bacteria that are capable of surviving pasteurization and are often nonpathogenic. Salmonella, Lactobacillus, and Escherichia coli, while bacteria commonly associated with the intestines, are not specifically known for their ability to survive pasteurization and being nonpathogenic in nature.