Week 5: Definitions

Chapter 8: Recombinant DNA Technology

Here are three types of artificial methods to introduce DNA into cells:

Electroporation: A method that uses an electrical current to puncture microscopic holes through a cell's membrane so that DNA can enter the cell from the environment.

Protoplast Fusion: A method that exposes protoplasts to polyethylene glycol to increase the rate of fusion. The fusion of protoplasts allows the cytoplasmic membrane of both bodies to fuse to form a single cell that contains the genomes of both "parent cells."

Injection: There are two types of injection methods
a. Gene Gun: A device powered by a blank .22-caliber cartridge or compressed gas to fire tiny gold beads (covered with DNA) to a target cell.
b. Microinjection: DNA is inserted to a target cell with a glass micro-pipette having a tip diameter smaller that that of the cell or nucleus.

 
*Protoplast Fusion

Week 4: Observation

This past week in microbiology lab, we cultured different plates with certain bacteria. One method that we learned was the isolation streaking. The purpose of isolation streaking is to create isolated colonies of bacteria.

In the isolation streaking, the bacteria is collected by using a sterile inoculating loop. Once collected, the streaking occurs in four quadrants. The first quadrant contains the first contact of the inoculating loop. After the streak was made, the inoculating loop is then heated by the incinerator. After the loop in sterile again, the second quadrant is filled with the similar streak patter as the first. Instead of collecting the bacteria again from the original source, the bacteria is collected from the first quadrant by dragging the inoculating loop from the first quadrant. The same process is repeated for the third quadrant and bacteria is dragged from the second to third quadrant and the fourth quadrant has bacteria from the third quadrant's streak.

Week 3: Investigation

Different Types of Bacteria Based on Temperature Tolerance

This past week, we learned about different classifications of bacteria. One classification in particular was on which bacteria grow in certain temperature ranges. Listed below are four types of bacteria that we learned in class, in addition to an extra group:

• Psychrophiles can grow at 0° C but optimum is about 15° C.
• Psychrotrophs can grow at 0° C also but optimum is 20 - 30° C – (important in food spoilage).
• Mesophiles grow best at moderate around 37° C – (many pathogens fall in this category).
• Thermophiles have a growth optimum at around 60° C.
• Hyperthermophiles have growth optima of 80° C or higher.