Wolbachia Investigation Post

Wolbachia is known as a genus of bacteria that specifically infect insects or nematodes. Wolbachia is currently being studied because scientists and researchers are seeing an increase in the feminization of populations, a trend that can be attributed to Wolbachia. In addition, Wolbachia is an interest of study because the bacteria are being noticed as a possible way to eliminate Dengue since mosquito eggs are eliminated by an intracellular incongruity when an infected male mates with a non-infected female.

Wolbachia acts as a parasite to insects, specifically an endosymbiotic parasite; this means that Wolbachia actively lives inside insect (and nematode) cells. Wolbachia can be transferred both horizontally and vertically through insects, meaning that the bacteria can be transmitted between different arthropods or via inheritance (through female eggs). Since Wolbachia cannot survive for long in an extracellular environment, the bacteria have acquired processes to increase transmission – one of these processes include changing the genders of the female’s eggs to all females. In addition, in varied populations of arthropods, females and males must have the same strain of Wolbachia bacteria in order to mate. Other species that have infected females do not need male sperm to reproduce, and the offspring are all female with the Wolbachia infection and identical DNA to the mother (parthogenesis).

The major impact of these processes on the environment is the feminization of insect populations. With more female insects in a population, the Wolbachia bacteria are able to proliferate easily; however, the insect population experiences disadvantages. For example, there is a possibility that some females might not be able to mate since the number of females could eventually be excessive over the quantity of males. In addition, specific populations that undergo parthogenesis would be much more vulnerable to elimination via natural selection since all the offspring and females would be genetically identical, and with a less diverse genetic range in a population, the more easily the population will become extinct.

   

The purpose of the lab was to utilize various lab procedures to identify whether collected insects were infected with the Wolbachia bacteria. To get the results, lab groups used skills such as micropipetting and operating a centrifuge in order to isolate insect DNA. A Lysis Buffer was used to break down insect cells and release DNA, and shortly afterwards, the resulting material was heated up in a heat block in order to denature proteins (including enzymes that digest DNA). By using the centrifuge, the DNA was in a liquid, separated from insoluble material. NaCl was used to bind to Lysis Buffer detergents that must be detached to obtain pure insect DNA; finally, with the addition of isopropanol, DNA precipitates. TE buffer is utilized to stabilize DNA, and RNase eliminates stray RNA that could interfere with the PCR step. In the PCR, the DNA that has been acquired and isolated is amplified, and a gel electrophoresis can be run to identify whether Wolbachia DNA was present in the insect.

The results from the lab can be found below:

Davis’ sample was the only one found to have Wolbachia DNA, but interestingly enough, the presence of insect DNA did not show up in the gel electrophoresis. This is an unexpected result since Wolbachia DNA is located in insect cells, so the presence of Wolbachia DNA should also come along with the presence of insect DNA.

Bharathi, Nicole and Marissa’s samples displayed the presence of insect DNA, while other samples with no “ladder” or stripes had no DNA present (or the DNA was not able to be seen in the gel electrophoresis). National studies have shown that about 16-22% of insects carry Wolbachia bacteria (about 1/5 of insects). In the samples from the class, about 1/12 of the collected insect samples carried Wolbachia bacteria. This could mean that Wolbachia bacteria do not proliferate as much in the Bay Area as they do in other areas of the world; however, taking into account the increasing rate of feminization of insect populations, future Team AP Bio students may see more insects infected with Wolbachia bacteria soon enough!

My experience in this lab was great! Although my lab group had some hiccups and problems along the way, I still learned a great deal of information about Wolbachia and running centrifuges and PCRs. I was surprised that we went through this lab much more easily than I thought; in the beginning of the semester, I had almost no idea what I was doing when it came to organizing all the colored tubes and micropipetting the correct amount of solutions. In this lab, I realized how much practice with micropipettes and biotech we had done during the year, and I was amazed when I felt significantly more confident when using biotech tools! I was truly surprised because the lab involved so many details and steps, and although our lab group accidentally did a step out of order, we performed the process involved with the steps well. This lab got me very excited for my future in biology, and I hope to use these skills I’ve learned in research at UCLA!