Genomic Signatures of Experimental Adaptation to Antimicrobial Peptides in Staphylococcus aureus.

The evolution of resistance against antimicrobial peptides has long been considered unlikely due to their mechanism of action, yet experimental selection with antimicrobial peptides (AMPs) results in rapid evolution of resistance in several species of bacteria. Although numerous studies have utilized mutant screens to identify loci that determine AMP susceptibility, there is a dearth of data concerning the genomic changes that accompany experimental evolution of AMP resistance. Using genome resequencing, we analyzed the mutations that arose during experimental evolution of resistance to the cationic AMPs iseganan, melittin, and pexiganan, as well as to a combination of melittin and pexiganan, or to the aminoglycoside antibiotic streptomycin.

Perspectives on the evolutionary ecology of arthropod antimicrobial peptides.

Antimicrobial peptides (AMPs) are important elements of the innate immune defence in multicellular organisms that target and kill microbes. Here, we reflect on the various points that are raised by the authors of the 11 contributions to a special issue of Philosophical Transactions on the 'evolutionary ecology of arthropod antimicrobial peptides'. We see five interesting topics emerging.

Antimicrobial defence and persistent infection in insects revisited.

Insects show long-lasting antimicrobial immune responses that follow the initial fast-acting cellular processes. These immune responses are discussed to provide a form of phrophylaxis and/or to serve as a safety measure against persisting infections. The duration and components of such long-lasting responses have rarely been studied in detail, a necessary prerequisite to understand their adaptive value.

Antimicrobial combinations: Bliss independence and Loewe additivity derived from mechanistic multi-hit models.

Antimicrobial peptides (AMPs) and antibiotics reduce the net growth rate of bacterial populations they target. It is relevant to understand if effects of multiple antimicrobials are synergistic or antagonistic, in particular for AMP responses, because naturally occurring responses involve multiple AMPs. There are several competing proposals describing how multiple types of antimicrobials add up when applied in combination, such as Loewe additivity or Bliss independence.

Locally rare species influence grassland ecosystem multifunctionality.

Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity-multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land-use intensity (LUI) gradient.

Spatial and niche-based ecological processes drive the distribution of endophytic Sebacinales in soil and root of grassland communities.

The interest in endophytic sebacinalean communities has been increasing during the last decade due to the increased knowledge about their symbiotic life style and potential role for ecosystem functioning. Although they are present in many ecosystems, their abundance in individual plant roots is very limited. This fact affects their study: they are difficult to isolate and to detect in root DNA samples.

Effects of mistletoe removal on growth, N and C reserves, and carbon and oxygen isotope composition in Scots pine hosts.

Most mistletoes are xylem-tapping hemiparasites, which derive their resources from the host's xylem solution. Thus, they affect the host's water relations and resource balance. To understand the physiological mechanisms underlying the mistletoe-host relationship, we experimentally removed Viscum album ssp.

Combination Effects of Antimicrobial Peptides.

Antimicrobial peptides (AMPs) are ancient and conserved across the tree of life. Their efficacy over evolutionary time has been largely attributed to their mechanisms of killing. Yet, the understanding of their pharmacodynamics both in vivo and in vitro is very limited.

A coastal and an interior Douglas fir provenance exhibit different metabolic strategies to deal with drought stress.

Drought is a major environmental stress affecting growth and vitality of forest ecosystems. In the present study, foliar nitrogen (N) and carbon (C) metabolism of two Douglas fir (Pseudotsuga menziesii) provenances with assumed different drought tolerance were investigated. We worked with 1-year-old seedlings of the interior provenance Fehr Lake (FEHR) originating from a dry environment and the coastal provenance Snoqualmie (SNO) from a more humid origin.

Community priming--effects of sequential stressors on microbial assemblages.

Microbes in nature are exposed to complex environmental stressors which challenge their functioning or survival. Priming is the improved reaction of an organism to an environmental stressor following a preceding, often milder stress event. This phenomenon, also known as cross-protection, predictive response strategy or acquired stress resistance, is becoming an increasingly well-established research topic in microbiology, which has so far been examined from the perspective of a single organism or population.