| Summary: | 碩士 === 國立彰化師範大學 === 生物學系 === 107 === Ophiocordyceps unilateralis (Clavicipitaceae: Hypocreales) also referred to as a zombie fungus, is a fungal pathogen and considered specific to ants of the tribe Camponotini (Formicinae: Formicidae) and currently found predominantly in tropical forest ecosystems. In this study, the Ophiocordyceps unilateralis sensu lato was found that it can infect a principal host ant species and seven alternative sympatric hosts in the forest of central Taiwan. For generalist parasitoids, it is very important to select host species that maximize their fitness. However, a generalist parasitoid fungus suffers a trade-off between host-range breadth, host encounter frequency and the physical barrier and immune system in different ant hosts. In this study, I use culture-dependent and -independent methods to capture different bacterial community fractions between a principal host ant species, Polyrhachis moesta, and an alternative sympatric host, Polyrhachis wolfi. In the culture-dependent data, the bacterial community composition in these two hosts were estimated at the phylum and genus levels. I found that the Bacillus spp. is the dominant bacteria in the bodies of these two ants. Interestingly, most of the Bacillus species we isolated are able to break down sheep's blood cells by a process called hemolysis. To quantify the activity of the hemolysis, we performed a co-culture experiment of an invertebrate model organism, Caenorhabditis elegans with those Bacillus species and calculated the survival rate of C. elegans to prove that the hemolytic bacteria do have an effect on invertebrate cell digesting. In addition, we also found out that those Bacillus species were more resistant than the bacteria isolated from the soil in the same habitat against natural naphthoquinones. In culture-independent data, the microbiota was not overlapping to the culture-dependent data, but more bacteria were found in infected ant hosts, moreover entomopathogenic bacteria Rickettsiella was found in P. wolfi. By analyzing the bacterial compostition, we are able to understand the tripartite interaction parasite, host, and microbes.
Key words: parasitism, generalist fungal parasitoid, zombie ant, Bacillus, microbiota
|
|---|
