Biology subjects

Papp, B.

Publications and source records attributed to Papp, B..

3 recordsLinked to original sources

bioRxiv2018

Phylogenetic barriers to horizontal transfer of antimicrobial peptide resistance genes in the human gut microbiota

The human gut microbiota has adapted to the presence of antimicrobial peptides (AMPs) that are ancient components of immune defence. Despite important medical relevance, it has remained unclear whether AMP resistance genes in the gut microbiome are available for genetic exchange between bacterial species. Here we show that AMP- and antibiotic-resistance genes differ in their mobilization patterns and functional compatibilities with new bacterial hosts. First, whereas AMP resistance genes are widespread in the gut microbiome, their rate of horizontal transfer is lower than that of antibiotic resistance genes. Second, gut microbiota culturing and functional metagenomics revealed that AMP resistance genes originating from phylogenetically distant bacteria only have a limited potential to confer resistance in Escherichia coli, an intrinsically susceptible species. Third, the phenotypic impact of acquired AMP resistance genes heavily depends on the genetic background of the recipient bacteria. Taken together, functional compatibility with the new bacterial host emerges as a key factor limiting the genetic exchange of AMP resistance genes. Finally, our results suggest that AMPs induce highly specific changes in the composition of the human microbiota with implications for disease risks.

microbiology↗

bioRxiv2018

Pathogen diversity drives the evolution of promiscuous peptide binding of human MHC-II alleles

Major histocompatibility complex (MHC) molecules mediate the adaptive immune response against pathogens. Certain MHC alleles are generalists: they present an exceptionally large variety of antigenic peptides. However, the functional implications of such elevated epitope binding promiscuity in the MHC molecules are largely unknown. According to what we term the pathogen-driven promiscuity hypothesis, exposure to a broad range of pathogens favors the evolution of highly promiscuous MHC variants. Consistent with this hypothesis, we found that in pathogen-rich geographical regions, humans are more likely to carry promiscuous MHC class II DRB1 alleles, and the switch between high and low promiscuity levels has occurred repeatedly and in a rapid manner during human evolution. We also show that selection for promiscuous peptide binding shapes MHC genetic diversity. In sum, our study offers a conceptually novel mechanism to explain the global distribution of allelic variants of a key human immune gene by demonstrating that pathogen pressure maintains promiscuous MHC class II alleles. More generally, our work highlights the hitherto neglected role of epitope binding promiscuity in immune defense, with implications for medical genetics and epidemiology.

evolutionary biology↗

bioRxiv2018

Enzyme promiscuity shapes evolutionary innovation and optimization

Evidence suggests that novel enzyme functions evolved from low-level promiscuous activities in ancestral enzymes. Yet, the evolutionary dynamics and physiological mechanisms of how such side activities contribute to systems-level adaptations are poorly understood. Furthermore, it remains untested whether knowledge of an organisms promiscuous reaction set ( underground metabolism) can aid in forecasting the genetic basis of metabolic adaptations. Here, we employ a computational model of underground metabolism and laboratory evolution experiments to examine the role of enzyme promiscuity in the acquisition and optimization of growth on predicted non-native substrates in E. coli K-12 MG1655. After as few as 20 generations, the evolving populations repeatedly acquired the capacity to grow on five predicted novel substrates-D-lyxose, D-2-deoxyribose, D-arabinose, m-tartrate, and monomethyl succinate-none of which could support growth in wild-type cells. Promiscuous enzyme activities played key roles in multiple phases of adaptation. Altered promiscuous activities not only established novel high-efficiency pathways, but also suppressed undesirable metabolic routes. Further, structural mutations shifted enzyme substrate turnover rates towards the new substrate while retaining a preference for the primary substrate. Finally, genes underlying the phenotypic innovations were accurately predicted by genome-scale model simulations of metabolism with enzyme promiscuity. Computational approaches will be essential to synthesize the complex role of promiscuous activities in applied biotechnology and in models of evolutionary adaptation.

systems biology↗