103 research outputs found
Intraspecific predation in immature Coenagrion puella (L.): a switch in food selection? (Zygoptera: Coenagrionidae)
Observations on cannibalism in outdoor insectaries are presented. The behavioural interactions are described. Cannibalism (in both sexes) occurred only during periods of cold weather. It is hypothesised that intraspecific predation is a switch in food selection due to bad weather conditions
Immune function keeps endosymbionts under control
How does an animal host prevent intracellular symbionts getting out of hand? A new paper in BMC Biology provides evidence that the mutualism between a beetle and its bacterial endosymbiont could be mediated through the expression of host immune genes
Exposure of Larvae of the Solitary Bee Osmia bicornis to the Honey Bee Pathogen Nosema ceranae Affects Life History
Wild bees are important pollinators of wild plants and agricultural crops and they are threatened by several environmental stressors including emerging pathogens. Honey bees have been suggested as a potential source of pathogen spillover. One prevalent pathogen that has recently emerged as a honey bee disease is the microsporidian Nosema ceranae. While the impacts of N. ceranae in honey bees are well documented, virtually nothing is known about its effects in solitary wild bees. The solitary mason bee Osmia bicornis is a common pollinator in orchards and amenable to commercial management. Here, we experimentally exposed larvae of O. bicornis to food contaminated with N. ceranae and document spore presence during larval development. We measured mortality, growth parameters, and timing of pupation in a semi-field experiment. Hatched individuals were assessed for physiological state including fat body mass, wing muscle mass, and body size. We recorded higher mortality in the viable-spore-exposed group but could only detect a low number of spores among the individuals of this treatment. Viable-spore-treated individuals with higher head capsule width had a delayed pupation start. No impact on the physiological status could be detected in hatched imagines. Although we did not find overt evidence of O. bicornis infection, our findings indicate that exposure of larvae to viable N. ceranae spores could affect bee development
Host and symbiont jointly control gut microbiota during complete metamorphosis
Holometabolous insects undergo a radical anatomical re-organisation during
metamorphosis. This poses a developmental challenge: the host must replace the
larval gut but at the same time retain symbiotic gut microbes and avoid
infection by opportunistic pathogens. By manipulating host immunity and
bacterial competitive ability, we study how the host Galleria mellonella and
the symbiotic bacterium Enterococcus mundtii interact to manage the
composition of the microbiota during metamorphosis. Disenabling one or both
symbiotic partners alters the composition of the gut microbiota, which incurs
fitness costs: adult hosts with a gut microbiota dominated by pathogens such
as Serratia and Staphylococcus die early. Our results reveal an interaction
that guarantees the safe passage of the symbiont through metamorphosis and
benefits the resulting adult host. Host-symbiont âconspiraciesâ as described
here are almost certainly widespread in holometobolous insects including many
disease vectors
Antimicrobial activity of cationic antimicrobial peptides against stationary phase bacteria
Antimicrobial peptides (AMPs) are ancient antimicrobial weapons used by multicellular organisms as components of their innate immune defenses. Because of the antibiotic crisis, AMPs have also become candidates for developing new drugs. Here, we show that five different AMPs of different classes are effective against non-dividing Escherichia coli and Staphylococcus aureus. By comparison, three conventional antibiotics from the main three classes of antibiotics poorly kill non-dividing bacteria at clinically relevant doses. The killing of fast-growing bacteria by AMPs is faster than that of slow-dividing bacteria and, in some cases, without any difference. Still, non-dividing bacteria are effectively killed over time. Our results point to a general property of AMPs, which might explain why selection has favored AMPs in the evolution of metazoan immune systems. The ability to kill non-dividing cells is another reason that makes AMPs exciting candidates for drug development
Is antimicrobial resistance evolution accelerating?
Globally, antimicrobials are a main pillar of medical, veterinary, and agriculture interventions [1,2]. In all cases, resistance of microbes against antimicrobials is prevalent. The problem is exacerbated by the drying up of the antibiotic pipeline, as economic incentives to develop new drugs are very limited. In antifungals, the range of available compounds is also low with only 4 main classes of drugs available to treat fungal infections in humans and 6 main classes used in agriculture, with 1 class, the azoles, used in both [1].
The problem of drug resistance evolution has been observed early on in the antibiotic era [3,4]. Ultimately, however, the introduction of each antimicrobial resulted in resistance evolution in target and nontarget microbes. In realization of this problem, some antibiotics such as daptomycin were even developed with avoiding resistance evolution in mind, yet it took only 2 years from the introduction of daptomycin until resistance was recorded [4]. But how fast is resistance evolving?
Here, we want to discuss how fast resistance emerges after the introduction of antimicrobials. We base this on widely cited data in the literature for antibiotics ([4â7]; see also Fig 1A, based on [8]) and compared this to data on antifungal resistance [9,10]. Replotting the antibiotic data (Fig 1B), by displaying the time from introduction to resistance emergence over the year of introduction, suggests that the evolution of antibiotic resistance is accelerating over time. The same trend can be observed for antifungals (Fig 1C and 1D). In the following, we focus on (1) the quality of the underlying data and (2) possible explanations for this pattern of accelerating resistance
Inducible Defenses Stay Up Late: Temporal Patterns of Immune Gene Expression in Tenebrio molitor
The course of microbial infection in insects is shaped by a two-stage process of immune defense. Constitutive defenses, such as engulfment and melanization, act immediately and are followed by inducible defenses, archetypically the production of antimicrobial peptides, which eliminate or suppress the remaining microbes. By applying RNAseq across a 7-day time course, we sought to characterize the long-lasting immune response to bacterial challenge in the mealworm beetle Tenebrio molitor, a model for the biochemistry of insect immunity and persistent bacterial infection. By annotating a hybrid de novo assembly of RNAseq data, we were able to identify putative orthologs for the majority of components of the conserved insect immune system. Compared with Tribolium castaneum, the most closely related species with a reference genome sequence and a manually curated immune system annotation, the T. molitor immune gene count was lower, with lineage-specific expansions of genes encoding serine proteases and their countervailing inhibitors accounting for the majority of the deficit. Quantitative mapping of RNAseq reads to the reference assembly showed that expression of genes with predicted functions in cellular immunity, wound healing, melanization, and the production of reactive oxygen species was transiently induced immediately after immune challenge. In contrast, expression of genes encoding antimicrobial peptides or components of the Toll signaling pathway and iron sequestration response remained elevated for at least 7 days. Numerous genes involved in metabolism and nutrient storage were repressed, indicating a possible cost of immune induction. Strikingly, the expression of almost all antibacterial peptides followed the same pattern of long-lasting induction, regardless of their spectra of activity, signaling possible interactive roles in vivo
Antimicrobials, Stress and Mutagenesis
Cationic antimicrobial peptides are ancient and ubiquitous immune effectors
that multicellular organisms use to kill and police microbes whereas
antibiotics are mostly employed by microorganisms. As antimicrobial peptides
(AMPs) mostly target the cell wall, a microbial âAchilles heelâ, it has been
proposed that bacterial resistance evolution is very unlikely and hence AMPs
are ancient âweaponsâ of multicellular organisms. Here we provide a new
hypothesis to explain the widespread distribution of AMPs amongst
multicellular organism. Studying five antimicrobial peptides from vertebrates
and insects, we show, using a classic Luria-Delbruš ck fluctuation assay, that
cationic antimicrobial peptides (AMPs) do not increase bacterial mutation
rates. Moreover, using rtPCR and disc diffusion assays we find that AMPs do
not elicit SOS or rpoS bacterial stress pathways. This is in contrast to the
main classes of antibiotics that elevate mutagenesis via eliciting the SOS and
rpoS pathways. The notion of the âAchilles heelâ has been challenged by
experimental selection for AMP-resistance, but our findings offer a new
perspective on the evolutionary success of AMPs. Employing AMPs seems
advantageous for multicellular organisms, as it does not fuel the adaptation
of bacteria to their immune defenses. This has important consequences for our
understanding of host-microbe interactions, the evolution of innate immune
defenses, and also sheds new light on antimicrobial resistance evolution and
the use of AMPs as drugs
Increased survival of experimentally evolved antimicrobial peptide-resistant Staphylococcus aureus in an animal host.
Antimicrobial peptides (AMPs) have been proposed as new class of antimicrobial drugs, following the increasing prevalence of bacteria resistant to antibiotics. Synthetic AMPs are functional analogues of highly evolutionarily conserved immune effectors in animals and plants, produced in response to microbial infection. Therefore, the proposed therapeutic use of AMPs bears the risk of âarming the enemyâ: bacteria that evolve resistance to AMPs may be crossâresistant to immune effectors (AMPs) in their hosts. We used a panel of populations of Staphylococcus aureus that were experimentally selected for resistance to a suite of individual AMPs and antibiotics to investigate the âarming the enemyâ hypothesis. We tested whether the selected strains showed higher survival in an insect model (Tenebrio molitor) and crossâresistance against other antimicrobials in vitro. A population selected for resistance to the antimicrobial peptide iseganan showed increased in vivo survival, but was not more virulent. We suggest that increased survival of AMPâresistant bacteria almost certainly poses problems to immuneâcompromised hosts
Emergence patterns of Coenagrion hastulatum (Charpentier) in northern Germany (Zygoptera: Coenagrionidae)
The emergence patterns were followed closely at a pond E of Braunschweig. The emergence period lasted 24 days and the EM50 was reached after 11 days. Due to its emergence phenology. C. hastulatum is classified as a summer species. The date of emergence was negatively correlated with head width in 9 2 but not in <J cj. In tJ <? , a negative correlation occurred between the date of emergence and the body mass at emergence. These findings are contrasting previous studies and are discussed with respect to sexual differences. The results are compared with the emergence patterns of other odonates
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