Microbio Quiz 5

What is bacterial transformation and what is its purpose?

the uptake of foreign DNA (a plasmid) by an organism, giving them new traits/genetic material (DNA).

What are the major steps in the transformation process, and what does each accomplish?

• CaCl₂ treatment: Makes bacteria competent to take up DNA.

• Ice incubation: Allows plasmid DNA to attach to the bacterial membrane.

• Heat shock: Creates temporary pores so plasmid DNA enters the cell.

• Recovery in LB broth: Allows bacteria to recover and express plasmid genes before plating.

• Plating on selective media: Determines which bacteria were successfully transformed.

What are the main parts of the pGLO plasmid and their functions?

• GFP gene: Produces green fluorescent protein.

• ampR gene: Provides resistance to ampicillin.

• P_BAD promoter: Turns GFP expression on only when arabinose is present.

• araC gene: Regulates the P_BAD promoter in response to arabinose.

How do the plasmid components produce the different results observed on the plates?

• ampR allows transformed bacteria to survive on ampicillin plates.

• GFP makes bacteria glow green.

• P_BAD + araC ensure GFP is only expressed when arabinose is present.

• Therefore, bacteria on LB/amp survive but do not glow, while bacteria on LB/amp/ara survive and glow.

What is the role of the antibiotic resistance gene (ampR)?

allows transformed bacteria to survive in the presence of ampicillin. It acts as a selectable marker, meaning only bacteria that successfully received the plasmid will grow on ampicillin-containing media.

How do you determine whether transformation was successful in pGLO experiment?

when bacteria grow on plates containing ampicillin. If arabinose is also present, the transformed bacteria will fluoresce green under UV light because the GFP gene is expressed.

food intoxication vs food infection

• food intoxication: microorganism is ingested and produces toxins that cause illness usually within 6-12 hours after ingestion

• food infection: microorganism is ingested and colonizes our digestive tract

the number of microorganisms indicates the foods general _____.

microbial quality; if microbial numbers are high, one can assume that a food’s quality is low and may contain pathogens.

What are various good practices to keep food safe?

1. clean food well (wash produce and meat)

2. clean your hands and the utensils used in preparing food

3. store food properly after preparation and prior to consumption

Van Delden’s Broth

anaerobic conditions and sulfate, enrichment for sulfate-reducing bacteria (growth produces black precipitate)

Bristol’s Broth

no carbon source, enrichment for algae and cyanobacteria

Chu’s Broth

no nitrogen source, enrichment for cyanobacteria

selective media

inhibits growth of undesired organisms so that only desired type can grow

enrichment media

favors the growth of the desired organism without deliberately repressing other forms.

differential media

distinguishes between different microorganisms in a mixed culture

microbial succession

growth of several types of microorganisms rise and fall in succession before the final product is formed

In sauerkraut:

As fermentation progresses, the microorganisms change the environment (especially by lowering the pH), allowing different microorganisms to become dominant. This natural succession preserves the cabbage and produces sauerkraut.

What are the roles of the ingredients involved in sauerkraut production?

• Brine: salty plant water extract, the salt helps select against possible contaminant gram negatives; water provides anaerobic environment that helps prevent fungal growth

• Cabbage: enriches for lactose fermenting gram positives

What is the threshold for possible UTI infection?

1×10^5 (100,000) cells per ml

midstream catch vs first-void urine samples

• midstream catch: (pee-pause-pee in cup) is going to target bacteria within the urinary tract; better for uti testing

• first-void: (pee in cup right away) is going to target bacteria of external genitalia; better for std testing

What are the 3 categories of defenses on the skin?

1. mechanical: skin, cilia, hair

2. chemical: stomach acid, sweat

3. microbial: antibiotics, resident bacteria

residential vs transient bacteria

• Residential: bacteria apart of our normal flora that are not harmful to us. Can actually be beneficial by preventing pathogenic organisms from harming us.

• Transient: microorganisms that we pick up from our environment and are poorly adapted to the skin surface

opportunistic pathogen

An opportunistic pathogen is a microorganism that is normally harmless and part of the body’s resident microbiota, but it can cause disease if it gets into the wrong place in the body or if the immune system is weakened.

Why is Staphylococcus aureus considered an opportunistic pathogen?

Staphylococcus aureus commonly lives on the skin and in the nose without causing disease. However, if it enters the body through a cut, wound, surgical incision, or bloodstream, it can cause infections such as skin infections, abscesses, pneumonia, or bloodstream infections.

How might our body’s defenses be dampened? (skin)

• not allowing skin to dry: no longer effective barrier; caused by humidity and excessive sweating, trapped moisture

• use of corticosteroids: decreases skins rate of shedding giving pathogens a longer time to be established

• injuries/skin wounds