Quiz 5 Flashcards
What is microbial succession and how does it work ?
- Microbial Succession - Growth of several types of microorganisms rise and fall in succession before the final product is formed
- Microbial succession is the process that uses microbes for fermentation of food and increases health benefits of that food
Which species are active at which point in the fermentation process (i.e. early,
intermediate, and late stages)? What are these bacteria doing?
- Early stage - Bacteria consume oxygen, create an anaerobic environment, and start acidifying the environment. Enterobacter cloacae and Erwinia herbicola
- Intermediate stage - Acid-tolerant bacteria dominate, producing lactic acid and stabilizing the fermentation.Leuconostic mesenteroides
- Late Stage - Highly acid-tolerant bacteria ensure the final product’s preservation and flavor development by maintaining a low pH. Lactobacillus
What are the general trends in terms of pH and flavor as the cabbage ferments?
As cabbage ferments, the pH decreases and total acidity increases
What is bacterial transformation and how does it work?
- Bacterial transformation is a genetic process that allows bacteria to absorb foreign DNA from their environment and express a new piece of genetic material
- DNA from ligation is put into a bacterial culture. The culture is heat shocked (Making the bacterial cells more competent). Plasmid is transformed into the bacteria. Grow the bacteria up on an all-purpose media. The bacteria expresses some type of protein as a result of the gene in the plasmid.
What are plasmids?
A genetic structure in a cell that can replicate independently of the chromosomes
What are the steps and reagents involved in transformation and how to they work? Why
is each step important in transformation?
What is competency? How did we make bacteria competent in this exercise?
- Competency is the ability of a bacterial cell to take up DNA through pores in its cell membrane.
- Heat shocking makes the bacteria more competent
How can you select for transformed bacteria?
by its ability to multiply and form colonies in the presence of the antibiotic
What plasmid did we use? Understand each of the genes that can be found in that plasmid
and why each is important.
Why is it important to quantify bacteria on food?
Because it determines the microbial quality of food
What is food intoxication? What is food infection? How do they differ? What are some
examples of organisms that causes these types of conditions?
Food infection - Microorganisms is ingested and colonizes our digestive tract
Food intoxication - Microorganisms is ingested and produces toxins that cause illness usually within 6-12 hours after ingestion
With food infections the microorganisms are ingested and grow within us, while with intoxication, bacteria produce toxins before its ingested
Examples - Salmonella (In raw poultry and eggs) and Listeria Monocytogenes (in unpasteurized milk and fresh soft cheese, causes brain swelling and meningitis in newborns)
Is food sterile?
No
What steps can be taken to minimize bacterial contamination of food?
- Clean food well
- Clean your hands and utensils
- Store food properly
What is enrichment?
Enabling a particular type of microorganism to grow faster than all others in the sample
What types of media did we use in this experiment?
- Van Deldens
- Bristrol
- Chus
