Week 3 - Xieyue Xiao

Experiments started to be on the track this week. This Tuesday morning, Dr. Satlin and I plated the first 15 samples together to look for Pseudomonas Aeruginosa colonization in patients' gut. Every sample will be cultured in/on four different media, Cetrimide agar, CVA agar, ChromCRE agar and Tryptic Soy Broth for enrichment. The liquid culture of TSB will be then plated on Cetrimide agar for selection. Below is a picture of the plates and culture tubes of the first batch. The plating brought a lot of results to read in the following days. Even though I can handle the whole experiments by myself now, but for plating reading, we usually do it together. I learned a lot from this part of the experiment. Dr. Satlin taught me about what do the colonies of different organisms look like and smell. The colonies have very different morphologies, like mucoid or flat/dry, spreading or round, large or tiny, and of course different colors and transparency. Researchers from Dr. Walsh lab also taught me a lot. They can tell different species just from the appearance and smell! It is not only interesting but also very useful to learn these traditional microbiology tricks. It is almost the fastest way to distinguish if the one on the plate is the one you want. Even though we always need to confirm by molecular techniques like MALDI and 16S sequencing, this can still help you save a lot of time.
Next week, we will start preparing the 16S sequencing libraries. We will also do oxidase test on the colonies we picked up from culturing and the oxidase winners will be sent to MALDI for the final confirmation!