Biology subjects

Rolff, J.

Publications and source records attributed to Rolff, J..

26 records · Page 2Linked to original sources

bioRxiv2020

Multi-step vs. single-step resistance evolution under different drugs, pharmacokinetics and treatment regimens

The success of antimicrobial treatment is threatened by the evolution of drug resistance. Population genetic models are an important tool in mitigating that threat. However, most such models consider resistance emergence via a single mutational step. Here, we assembled experimental evidence that drug resistance evolution follows two patterns: i) a single mutation, which provides a large MIC increase, or ii) multiple mutations, each conferring a small increase, which combine to yield high-level resistance. Using stochastic modeling we then investigated the consequences of these two patterns for treatment failure and population diversity under various treatments. We find that resistance evolution is substantially limited if more than two mutations are required and that the most efficacious drug type depends on the pharmacokinetic profile. Further, we demonstrate that, for resistance evolution in multiple steps, adaptive treatment, which only suppresses the bacterial population, is favored over aggressive treatment, which aims at eradication.

evolutionary biology↗

bioRxiv2020

Antimicrobial peptide induced-stress renders Staphylococcus aureus susceptible to toxic nucleoside analogues

Cationic antimicrobial peptides (AMPs) are active immune effectors of multicellular organisms and also considered as new antimicrobial drug candidates. One of the problems encountered when developing AMPs as drugs is the difficulty to reach sufficient killing concentrations under physiological conditions. Here, using pexiganan, a cationic peptide derived from a host defence peptide of the African clawed frog and the first AMP developed into an antibacterial drug, we studied if sub-lethal effects of AMPs can be harnessed to devise treatment combinations. We studied the pexiganan stress response of Staphylococcus aureus at sub-lethal concentrations using quantitative proteomics. Several proteins involved in nucleotide metabolism were elevated, suggesting a metabolic demand. We then show that S. aureus is highly susceptible to antimetabolite nucleoside analogues when exposed to pexiganan, even at sub-inhibitory concentrations. These findings could be used to enhance pexiganan potency while decreasing the risk of resistance emergence, and our findings can likely be extended to other antimicrobial peptides.

microbiology↗

bioRxiv2019

Bacteria primed by antimicrobial peptides develop tolerance and persist

Antimicrobial peptides (AMPs) are key components of innate immune defenses. Because of the antibiotic crisis, AMPs have also come into focus as new drugs. Here, we explore whether prior exposure to sublethal doses of AMPs increases bacterial survival and abets the evolution of resistance. We show that Escherichia coli primed by sublethal doses of AMPs develop tolerance and increase persistence by producing curli or colanic acid. We develop a population dynamic model that predicts that priming delays the clearance of infections and fuels the evolution of resistance. The effects we describe should apply to many AMPs and other drugs that target the cell surface. The optimal strategy to tackle tolerant or persistent cells requires high concentrations of AMPs and fast and long-lasting expression. Our findings also offer a new understanding of non-inherited drug resistance as an adaptive response and could lead to measures that slow the evolution of resistance.

evolutionary biology↗

bioRxiv2019

Non-lethal oxidative stress boosts bacterial survival and evolvability under lethal exposure

Unicellular organisms have the prevalent challenge to survive under oxidative stress of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). ROS are present as by-products of photosynthesis and aerobic respiration. These reactive species are even employed by multicellular organisms as potent weapons against microbes. Although bacterial defences against lethal and sub-lethal oxidative stress have been studied in model bacteria, the role of fluctuating H2O2 concentrations remains unexplored. It is known that sub-lethal exposure of Escherichia coli to H2O2 results in enhanced survival upon subsequent exposure. Here we investigate the priming response to H2O2 at physiological concentrations. The basis and the duration of the response (memory) were also determined by time-lapse quantitative proteomics. We found that a low level of H2O2 induced several scavenging enzymes showing a long half-life, subsequently protecting cells from future exposure. We then asked if the phenotypic resistance against H2O2 alters the evolution of resistance against oxygen stress. Experimental evolution of H2O2 resistance revealed faster evolution and higher levels of resistance in primed cells. Several mutations were found to be associated with resistance in evolved populations affecting different loci but, counterintuitively, none of them was directly associated with scavenging systems. Our results have important implications for host colonisation and infections where microbes often encounter reactive oxygen species in gradients.

evolutionary biology↗

bioRxiv2018

A constitutively expressed antifungal peptide protects Tenebrio molitor during a natural infection by the entomopathogenic fungus Beauveria bassiana.

Antimicrobial peptides have been well studied in the context of bacterial infections. Antifungal peptides have received comparatively less attention. Fungal pathogens of insects and their hosts represent a unique opportunity to study host-pathogen interactions due to the million of years of co-evolution they share. In this study, we investigated role of a constitutively expressed thaumatin-like peptide with antifungal activity expressed by the mealworm beetle Tenebrio molitor, named Tenecin 3, during a natural infection with the entomopathogenic fungus Beauveria bassiana. We monitored the effect of the expression of Tenecin 3 on the survival of infected hosts as well as on the progression of the fungal infection inside the host. Finally, we tested the activity of Tenecin 3 against B. bassiana. These findings could help improving biocontrol strategies and help understanding the evolution of antifungal peptides as a defense mechanism.

immunology↗

bioRxiv2017

Genomic signature of experimental adaptation of Staphylococcus aureus to a natural combination of insect antimicrobial peptides

Antimicrobial peptides are highly conserved immune effectors across the tree of life and are employed as combinations. In the beetle Tenebrio molitor, a defensin and a coleoptericin are highly expressed in vivo after inoculation with S. aureus. The defensin displays strong in vitro activity but no survival benefit in vivo. The coleoptericin provides a survival benefit in vivo, but no activity in vitro. To investigate this paradox we experimentally evolved S. aureus to increased resistance against the defensin and a combination of the defensin and coleoptericin. Genome re-sequencing showed that resistance was associated with mutations in either the ytr or nsa operons, in both AMP treatments. Strains with these mutations show longer lag phases, slower Vmax and nsa mutants reach lower final population sizes. Mutations in rpoB were showed a further increase in the lag phase in nsa mutants but not in ytr mutants. In contrast, final MICs do not segregate by mutation. All resistant lines display AMP but not antibiotic cross-resistance. Costly resistance against AMPs readily evolves for an individual AMP as well as a naturally occurring combination in vitro and provides broad protection against AMPs. Such non-specific resistance could result in strong selection on host immune systems that rely on cocktails of AMPs.

evolutionary biology↗

bioRxiv2017

Predicting Drug Resistance Evolution: Antimicrobial Peptides Vs. Antibiotics

Antibiotic resistance constitutes one of the most pressing public health concerns. Antimicrobial peptides of multicellular organisms are considered part of a solution to this problem, and AMPs produced by bacteria such as colistin are last resort drugs. Importantly, antimicrobial peptides differ from many antibiotics in their pharmacodynamic characteristics. Here we implement these differences within a theoretical framework to predict the evolution of resistance against antimicrobial peptides and compare it to antibiotic resistance. Our analysis of resistance evolution finds that pharmacodynamic differences all combine to produce a much lower probability that resistance will evolve against antimicrobial peptides. The finding can be generalized to all drugs with pharmacodynamics similar to AMPs. Pharmacodynamic concepts are familiar to most practitioners of medical microbiology, and data can be easily obtained for any drug or drug combination. Our theoretical and conceptual framework is therefore widely applicable and can help avoid resistance evolution if implemented in antibiotic stewardship schemes or the rational choice of new drug candidates.

evolutionary biology↗

bioRxiv2017

Clay-induced DNA double-strand breaks underlay genetic diversity, antibiotic resistance and molecular basis of asbestosis

Some natural clays and synthetic nanofibres present in the environment have a severe impact on human health. After several decades of research, the molecular mechanism of how asbestos induce cancers is not well understood. Different fibres, including asbestos, can penetrate the membrane and introduce DNA in both, bacterial and eukaryotic cells. Incubating Escherichia coli with sepiolite, a clayey material, and asbestos under friction forces, both fibres cause double-strand breaks in bacteria. Since antibiotics and clays are used together in animal husbandry, the mutagenic effect of these fibres might constitute a pathway to antibiotic resistance due to the friction provided by peristalsis of the gut from farm animals in addition to the previously proposed horizontal gene transfer. Moreover, we raise the possibility that the same mechanism could generate bacteria diversity in natural scenarios with a role in the evolution of species. Finally, we provide a new model on how asbestos may promote mutagenesis and cancer based on the observed mechanical genotoxicity.

evolutionary biology↗