Spatial and Temporal Variation of Wolbachia in Aedes albopictus

1. Patrick R Murphy, Dr. Steven Juliano, Dr. Sabine Loew Introduction Methods Wolbachia is a group of bacteria that are inherited intracellularly. This group of bacteria affect a wide range of arthropods. The reason this group of bacteria have been able to remain within the mosquito populations is because they use a relatively novel evolutionary strategy,which is reproductive parasitism. The Wolbachia infection has been able to spread because it changes the reproductive success of itshost. Infected females gain a reproductive advantage over uninfected females because infected females can reproduce via insemination by either uninfected males or infected ones, but uninfected females can only reproduce via insemination by uninfected males. Eventually, one would expect to see a rise in Wolbachia infection because there are just not as many successful fertilizations in uninfected females. Genomic DNA was extracted from individual Aedesalbopictusmosquitoes. Following that process, the DNA was amplified under optimal Polymerase Chain Reaction conditions (PCR) (Figure 1). The DNA was amplified for the primers Wsp 16S, Wlb A, and Wlb B. Once PCR was completed, the amplified DNA was run on a 1.5% agarose gel to determine what strain was present in each mosquito. Amplification of Wsp 16S was performed first for each mosquito as Wsp 16S primers will amplify any strain of Wolbachiaand thereforeserve as a positive control. Following that, DNA from each mosquito was amplified with the strain-specific primersWlb A and Wlb B, therefore determining what type of Wolbachiastrainwas present in each mosquito. The picture below shows a typical agarose gel with EtBr stained PCR fragments (Figure 2); the first lane shows the size standard. The Wlb A strain is recognized as a 470 base pair fragment and the Wlb B strain is shown as the shorter fragment of 460 base pairs in length. Spatial and Temporal Variation of Wolbachia in Aedesalbopictus Figure 2: PCR fragments of Wlb A and B strains. Wlb A fragments are shown above Wlb B fragments. Figure 1: Illustration of amplification of DNA fragments e) Objectives Significance The objectives of this study are: Analyze the frequency of Wolbachia infection within Aedesalbopictusacross three different years within the same localities. Obtaining multi-year frequency data of infections will allow me to determine potential temporal variation of the two strains of Wolbachia within a few mosquito populations. Analyze the frequency of Wolbachia infection within Aedes albopictus across several localities of the same time period. Obtaining frequency data for several localities within the same year will allow me to determine the spatial variation of the two different strains of Wolbachia within one year. This study has significance when it comes to pest control. Wolbachia limits a host population via the shortening of the life span of adults. If Wolbachia could be introduced intoa population, then it could reduce the fitness of the mosquitoes and drive down their numbers. Wolbachia has also been reported to cause early death of male embryos. As the population of mosquitoes continues to breed, the largest frequency of that population will be infected females who either are breeding and losing many of their embryos, or are not breeding successfully as only fertilization by uninfected males would be successful. ThereforeWolbachia introduction into a population of mosquitoes could really decrease the fitness and the frequency of mosquitoes. Study sites Preliminary Results Mosquitoes were collected from vases at cemetery sites within Tampa, FL (Figure 3.). Some of the cemeteries were: Woodlawn, Oak Hill, Austriano-Centurian, Rosehill, North 25th, and Myrtle Hill Cemetery. Most of the sites were sampled in 2003, 2005, 2006, and 2009. Resultsshow that there is no significant difference in the frequency of Wolbachiastrainsamong populations around Tampa. Sexes differed in the frequency of A, B, AB and there was a significant relationship between the sex of the mosquito and the sampling year. The Wlb B strain of Wolbachia was higher in frequency for the years 2005 to 2006. However, the Wlb B strain declined in males in the same time frame. Figure 3. References Acknowledgements Preliminary Conclusions Dr. KavithaDamal Dr. Erik Larson Dr. Rachel Bowden Barry, A. (2010, May 6). Bmore Scientific. Charm City Current. Retrieved September 22, 2010, from charmcitycurrent.com/bmorescientific/ Bourtzis, K., & O'Neill, S. (1998). Wolbachia Infections and Arthropod Reproductions. BioScience, 48(4), 287-293. Jeong, G., & Suh, E. (2008). Wolbachia-induced Reproductive Anomalies and Their Future Applications. Entomological Research, 38, 41-48. Marshall, J. (n.d.). Gene drive systems for spreading refractory genes. John Marshall. Retrieved September 23, 2010, from http://johnmm.bol.ucla.edu/geneDrive.htm OBGYN Academy. (n.d.). Human Genetics. Retrieved September 23, 2010, from www.obgynacademy.com/basicsciences/fetology/genetics/ Reiter, P., Amador, M. A., Anderson, R. A., & Clark, G. G. (1995). Short Report: Dispersal of AedesAegypti in an Urban Area after Blood Feeding as Demonstrated by Rubidium-Marked Eggs. The American Journal of Tropical Medicine and Hygiene , 52(2), 177-179. StateMaster - Maps of Florida (31 in total). (n.d.). StateMaster - USA maps (1,144 state maps). Retrieved September 23, 2010, from http://maps.statemaster.com/state/FL/1 The Wolbachia strain B seems to be killing off males while not affecting females. Females who have strain B tend to not lose fitness whereas males do and therefore males have a higher fitness if infected with Wolbachia strain A as compared to Wolbachia strain B. This study supports the idea that Wolbachia strains differ in their capacity to shorten the life span of adult male versus adult female mosquitoes, and therefore differentially affect the probability of acting as vectors.