Abstracts (first author)

Talk 

Phage therapy might not help everyone; bacterial resistance and phage infectivity evolution considerably varies between different Cystic Fibrosis patients

Author(s): Friman V, Soanes-Brown D, Sierocinski P, Johansen HH, Molin S, Buckling A

Summary:

Phage therapy, the use of viruses to specifically kill only the disease-causing bacteria, could offer an alternative way to fight against antibiotic resistant bacteria. Even though phage selection could lead to increased bacterial resistance, phage therapy has the potential to become an evolutionary sustainable medicine: phages can coevolve more infective and thus retain their efficiency to keep bacteria under control. Here we studied experimentally in vitro the long-term coevolutionary dynamics of model phage therapy by using four natural phage species and Pseudomonas aeruginosa bacterial strains isolated from the lungs of ten Cystic Fibrosis patients. We found that bacteria and phages coevolved during the three weeks of cocultivation. However, coevolution was asymmetric by favouring bacterial resistance over phage infectivity, which suggests that phages might not be able to overcome bacterial resistance evolution indefinitely. When ancestral and coevolved phages were applied continuously to ancestral bacterial cultures, coevolved phages were clearly more efficient in reducing bacterial densities with lower corresponding increase in bacterial resistance. These results demonstrate that environmentally derived phages could be used to eradicate clinical bacterial infections, while the effectiveness of phage therapy could be enhanced by coevolving phages more infective in vitro. Despite this potential, our study also shows an important caveat: phages’ ability to reduce bacterial densities varied considerably between different patients having very large to negligible effects. As a result, phage therapy is unlikely to work uniformly across all patients and might need to be adjusted case-specifically according to given host and parasite genotypes. Recognising between-patient variation in bacteria-phage coevolution is thus crucial for developing a broad-spectrum phage therapy, which is effective against multiple pathogen genotypes.



Abstracts (coauthor)

Fluctuating temperature leads to evolution of thermal generalism and pre-adaptation to novel environments

Author(s): Ketola, T, Mikonranta L, Zhang J, Saarinen K, Friman V, Örmälä A, Mappes J, Laakso J

Summary:

Climate change scenarios do not only expect elevated temperatures but also increased temperature fluctuations. Environmental fluctuations are suggested to select for low levels of plasticity in fitness that is also hypothesized to increase organisms’ ability to invade novel environments and affect virulence of pathogens. We tested these hypotheses and show that across a range of temperatures, opportunistic bacterial pathogen Serratia marcescens that evolved in fluctuating temperature (daily variation between 24 and 38 °C, mean 31 °C), outperforms strains that evolved in constant temperature (31° C) across all measured temperatures. Their better growth was also evident in novel environments with parasitic viruses and predatory protozoans. However, the strains from fluctuating environment were less virulent to Drosophila melanogaster host. Therefore, whilst supporting the hypothesis that evolution in fluctuating environments is paired with tolerance to several novel environments, our results show that adapting to fluctuating environments can also be costly in terms of reduced virulence. Together these results suggest that thermal fluctuations driven by the climate change could affect not only species thermal tolerance but also species’ invasiveness and virulence.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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