What in the World is Wolbachia?

For our very last AP Biology lab EVER, my class looked into a very interesting type of bacteria: Wolbachia. Wolbachia is a genus of intracellular bacteria that lives inside the bodies of arthropods and nematodes. Wolbachia bacteria must live and reproduce inside the of insect host cells, as they are endosymbiotic. What exactly does Wolbachia do? Well that is both simple and complicated – Wolbachia bacteria alters the sex of their hosts, usually from male to female.

When I first heard what Wolbachia did, I genuinely could not believe it. How could a bacteria alter gender?? After doing some research, I discovered a few different ways:

1. In some species, infection of Wolbachia bacteria can cause females to reproduce parthenogenetically, meaning that eggs can develop without male fertilization. This would mean that the resulting offsprings would be genetically identical to the mother; they would all be female as well. Wolbachia causes the cells to stop mitosis at anaphase, when the two sets of chromosomes are suppose to separate, which leads to diploid nucleuses. This does not allow the duplicated chromosomes to separate, and thus results in a diploid female.

2. In some species, Wolbachia infections causes fertilized eggs to always develop as female by suppressing the production of masculinizing hormones. This makes it so genetically male embryos develop as females.

3. In some species, Wolbachia causes male embryos to abort in early development. This does not directly change a particular insect’s gender, but it does contribute to the overall feminization effect of Wolbachia.

As you can probably infer, Wolbachia bacteria reside in the reproductive systems of arthropods. Something even more interesting about Wolbachia is that it can be transmitting two ways: horizontally through contact with another organism or the environment , or more commonly, through the female’s eggs. Males cannot pass the bacteria to their offspring due to the absence of eggs in males. As mentioned previously, Wolbachia is a parasite in arthropods. Parasitism is when one organism benefits at the expense of the other – in this instance, the Wolbachia lives and reproduces inside of the reproductive organs of insects and some other arthropods, but causes an effect to the body. Interestingly enough, Wolbachia isn’t always considered a parasite: Inside filarial nematode hosts, Wolbachia is mutualistic – both organisms benefit.

Some of our Lab Equipment 

For this lab, we all went home and captured insects to use for samples and data. The purpose of this lab was to determine if any of these insects have Wolbachia DNA. This lab was like a master lab, involving many types of biotechnology that we have experimented with over the year. We began by crushing the insects’ thoraxes (where their reproductive organs lie) in a lysis solution. We then added DNA primer and a “master solution”, which contained free nucleotides. We ran these samples in a thermocycler to conduct PCR. The process of PCR (polymerase chain reaction) is used to amplify two regions of the DNA so that we could later successfully isolate the Wolbachia data. After the PCR, we began gel electrophoresis to see the results of these amplified products. The presence or absence of the genes on the gel served as date for us to determine whether or not the insects were infected with the Wolbachia parasite. The results of the gel electrophoresis are shown below.

I (Marissa) worked with Davis and Elina, and out of all of the groups, ours seemed to be the most successful in getting accurate data. From our results we can conclude that my insect (found in San Francisco by the other biology teacher) did not contain Wolbachia DNA while Davis’ did. As you can see, only one other person seemed to find Wolbachia DNA, and many other groups were not able to successfully extract insect DNA at all.

Me holding my Data Sample!

I very much enjoyed this lab. I will admit, there were a lot of steps, and some of it was extremely confusing. However, I could definitely tell that this was a very good lab to review all of the technology and lab experiments we had done all year. We used micropipettes, gel electrophoresis, and various machines to conduct PCR. In a perfect world, there would have been more data from the rest of our class so that we could tell the frequency of Wolbachia in our area. I think Wolbachia is an incredibly interesting genus of bacteria, and I am glad that we got to learn about it at all. I was very proud of myself for participating with the micropipettes on this last lab – usually I am too shaky to do it, but this time I was able to relax and compose myself in order to do it. What a great lab to end the year with!

Future AP Biology Team

My friend Davis Whalen and I created a video for future AP Biology students! We used iMovie with a video-vlog approach to discuss our summary of the year, and any advice for the students of next year. Enjoy!

The Mysterious Case of Bob Bacon

Our AP Biology class recently dissected fetal pigs as a way to interactively learn about the systems of the body. After doing so, we split up into groups of five to create a CSI mystery on how one of the pigs died. We created a story line, made up interactive clues, and set up a presentation where the class went to each of the stations to find the clues and attempt to figure out who killed the pig, how, and what body system was affected.

I worked with Amanda, Bharathi, Abi, and Jen S. Our system was the immune system, and we called our dead pig Bob Bacon. We set up his death as a murder mystery, starting off with a Breaking News TV Clip explaining that scientist Bob Bacon has died, and that the police had five possible suspects – all of which were his neighbors. The class was then asked to help out with investigations by visiting each of the “homes” of these suspects and determining who could be guilty based on the timeline, Bob’s medical record, and outside information. After spending about 7 minutes at each table, we reconvened as a class and asked everyone to collaborate and guess who the murderer may have been. We then released two more Breaking News Forecasts, which led the class to conclude that one of the scientists was responsible for giving Bob Bacon HIV 10 years ago, and that it was actually Bob’s cat who killed Bob by transmitting a disease. This disease, called toxoplasmosis, was able to kill Bob because his immune system was weakened from the HIV, which had eventually turned into AIDS. Here is our intro video which set up the scene for the project!

This was definitely one of the hardest projects I have ever had to do. The fact that it was a group project, even though I love all the members of our class, made it that much more difficult. Unfortunately, I was sick during most of the time that we got to work on this project during class, so our group was forced to utilize social media in order to communicate. Even with that disadvantage, I would say that we still did a great job! I enjoyed the creativity allowed through this project. I was able to throw in a lot of special touches and puns (such as the pigs name – ex. Connor Mc. Snorts) which delighted me and (hopefully) amused everyone else. It was interesting that we had to make some sort of wild connection that was so abstract that the class would most likely not be able to guess it at first, and THEN have to actually make them guess it within the time period. I am disappointed that I was not able to see the other groups’ projects (I hate being sick!) but I can only imagine that they were fantastic!