Browsing by Subject "saalistus"

Diverse ecological interactions between populations have a considerable impact on the composition and evolution of microbial communities. Microbial evolution can happen in such short timescales that the evolutionary and coevolutionary events occurring in the populations, in turn, affect the ecological interactions in the communities. Predation and competition are the two most important factors affecting the composition and evolution of microbial communities, and usually they are strongly dependent on each other. The aim of this work was to study the effects of a predatory ciliate, Tetrahymena thermophila, on the composition and activity of a synthetic bacterial community, and to compare the differences between the effects of an ancestral strain and a coevolved strain that had previously coevolved with Pseudomonas fluorescens SBW25. Another aim of this study was to examine whether the rapidly evolving P. fluorescens bacterial strain has any definitive impact on the composition of the synthetic multi-strain bacterial community, and what are the differences between the effects of ancestral, evolved and coevolved populations of the bacterium. The effects of the different treatments were studied by measuring bacterial and ciliate population densities and community activity, and with 16S rRNA gene sequence analysis of different timepoints in the experiment. Predation had a significant effect on community composition, activity and bacterial population densities. The effect of the coevolved predator on the community composition was weaker than the effect of the ancestral predator, which was most likely caused by the smaller population density of the coevolved predator. Possibly because of this, there was no significant difference in community activity, diversity or bacterial population densities between the predator treatments. Thus, for this part, the results were consistent. P. fluorescens had a small effect on the community composition, and the difference in the evolutionary history of the P. fluorescens populations had a significant effect on the metabolic activity of the community. The experimental results indicated that prior coevolution between P. fluorescens and T. thermophila can have possible notable effects on the composition and metabolic activity of a bacterial community. The impact of earlier evolutionary adaptation or possible coevolution between community parties should be taken into consideration when studying ecological interactions and evolutionary changes in microbial communities.