Abstracts (first author)
Evolution of natural microbial populations in traditional fermented productsPDF
I will present results on the evolution of microbial communities in traditional fermented products from Zambia. These products are produced by transferring a fraction of a former batch to initiate a new batch of product. In this way, microbial communities are allowed to evolve of large numbers of generations. Local villagers maintain independent replicate product lineages.
Methods. I have sampled three different traditional products (based on either milk or maize) from across Zambia, obtaining a total of 36 samples. I have established the community composition of the products and compared this composition for different samples of the same product type and different product types. In the laboratory, we have propagated the microbial communities for an additional two months under various conditions and have monitored changes in community composition.
Results. Our results show that the microbial flora is dominated by around 6 species of lactic acid bacteria and that specific combinations of species result into stable communities. I show that both geography and anthropogenic factors affect community composition in products collected from Zambia. Laboratory experiments propagating communities over two months show specific shifts in community structure that is consistent over all nine independent communities.
Conclusions. Traditional fermented products are very powerful experimental systems to study long-term properties of entire microbial communities. From the field sampling study we conclude that both environmental factors (that differ by geography) and anthropogenic factors are key in shaping microbial communities. From the laboratory studies we conclude that these communities are very stable in the long-term. This work opens up a range of possible follow-up projects. We will perform manipulative experiments in the field as well as in the laboratory to establish exactly what factors are essential for community stability.
Advantages of sex beyond recombination in a fungal modelPDF
Why sexual reproduction is so prevalent in nature remains a major question in evolutionary biology. Most of the proposed advantages of sex rely on the benefits obtained from recombination. However, it is still unclear whether the conditions under which these recombinatorial benefits would be sufficient to maintain sex in the short term are met in nature. Our study addresses a largely overlooked hypothesis, proposing that sex could be maintained in the short term by advantages due to functions associated with sex, but not related to recombination. These advantages would be so essential that sex could not be lost in the short term. Here, we used the fungus Aspergillus nidulans to experimentally test predictions of this hypothesis. Specifically, we were interested in (1) the short-term deleterious effects of recombination (2) possible non-recombinatorial advantages of sex particularly through the elimination of mutations, and (3) the outcrossing rate under choice conditions in a haploid fungus able to reproduce by both: outcrossing and haploid-selfing. Our results were consistent with the hypothesis: we found that 1) recombination can be strongly deleterious in the short term; 2) sexual reproduction between individuals derived from the same clonal lineage provided non-recombinatorial advantages likely through a selection arena mechanism.