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Berlin Brandenburg

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  • 1
    Language: English
    In: Evolution, 1 March 2013, Vol.67(3), pp.900-907
    Description: Selection imposed by coinfection may vary with the mechanism of within-host competition between parasites. Exploitative competition is predicted to favor more virulent parasites, whereas interference competition may result in lower virulence. Here, we examine whether exploitative or interference competition determines the outcome of competition between two nematode species (Steinernema spp.), which in combination with their bacterial symbionts (Xenorhabdus spp.), infect and kill insect hosts. Multiple isolates of each nematode species, carrying their naturally associated bacteria, were characterized by (1) the rate at which they killed insect hosts, and by (2) the ability of their bacteria to interfere with each other's growth via bacteriocidal toxins called "bacteriocins." We found that both exploitative and interference abilities were important in predicting which species had a selective advantage in pairwise competition experiments. When nematodes carried bacteria that did not interact via bacteriocins, the faster killing isolate had a competitive advantage. Alternatively, nematodes could gain a competitive advantage when they carried bacteria able to inhibit the bacteria of their competitor. Thus, the combination of nematode/bacterial traits that led to competitive success depended on which isolates were paired, suggesting that variation in competitive interactions may be important for maintaining species diversity in this community.
    Keywords: Biological sciences -- Biology -- Zoology ; Biological sciences -- Biology -- Parasitology ; Biological sciences -- Biology -- Microbiology ; Physical sciences -- Chemistry -- Chemical compounds ; Health sciences -- Medical conditions -- Infections ; Biological sciences -- Biology -- Evolutionary studies ; Biological sciences -- Biology -- Genetics ; Biological sciences -- Biology -- Microbiology ; Biological sciences -- Ecology -- Ecological processes ; Biological sciences -- Ecology -- Ecological processes
    ISSN: 00143820
    E-ISSN: 15585646
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  • 2
    Language: English
    In: The American Naturalist, March, 2010, Vol.175(3), p.374(8)
    Keywords: Microbial Colonies -- Research ; Bacteriocins -- Research ; Comorbidity -- Research
    ISSN: 0003-0147
    Source: Cengage Learning, Inc.
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  • 3
    In: Evolution, November 2010, Vol.64(11), pp.3198-3204
    Description: Spite occurs when an individual harms itself in the act of harming other individuals. Such behaviors were once assumed to be of limited evolutionary importance, as the conditions for the evolution of spite were thought to be too restrictive. Recent theoretical work, however, suggests that spatial population structure, which allows local competition among genotypes, could favor the evolution of spite. One of the clearest examples of spite is the costly production and release by bacteria of toxins (called bacteriocins) that can kill unrelated strains of the same species. Here, we establish the existence of spatial structure in two natural populations of bacteriocin‐producing bacteria. Specifically, relatedness decreased with increasing spatial distance between the field isolates. In addition, toxin‐mediated inhibitions were found only between isolates that were collected more than 1 m apart and that were generally less than 80% similar in their genomic fingerprints. Taken together, the results suggest that the bacteria are spatially structured, with mixing of genotypes and spiteful interactions at the boundaries between demes.
    Keywords: Bacteriocins ; Entomopathogenic Bacteria ; Genetic Variation ; Population Structure
    ISSN: 0014-3820
    E-ISSN: 1558-5646
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  • 4
    In: Evolution, March 2013, Vol.67(3), pp.900-907
    Description: Selection imposed by coinfection may vary with the mechanism of within‐host competition between parasites. Exploitative competition is predicted to favor more virulent parasites, whereas interference competition may result in lower virulence. Here, we examine whether exploitative or interference competition determines the outcome of competition between two nematode species ( spp.), which in combination with their bacterial symbionts ( spp.), infect and kill insect hosts. Multiple isolates of each nematode species, carrying their naturally associated bacteria, were characterized by (1) the rate at which they killed insect hosts, and by (2) the ability of their bacteria to interfere with each other's growth via bacteriocidal toxins called “bacteriocins.” We found that both exploitative and interference abilities were important in predicting which species had a selective advantage in pairwise competition experiments. When nematodes carried bacteria that did not interact via bacteriocins, the faster killing isolate had a competitive advantage. Alternatively, nematodes could gain a competitive advantage when they carried bacteria able to inhibit the bacteria of their competitor. Thus, the combination of nematode/bacterial traits that led to competitive success depended on which isolates were paired, suggesting that variation in competitive interactions may be important for maintaining species diversity in this community.
    Keywords: Allelopathy ; Bacteriocins ; Coexistence ; Coinfection ; Diversity ; Entomopathogenic Nematodes ; Exploitative Competition ; Interspecific Competition ; Steinernema ; Xenorhabdus
    ISSN: 0014-3820
    E-ISSN: 1558-5646
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  • 5
    In: Ecology, May 2014, Vol.95(5), pp.1173-1183
    Description: While host‐species diversity often influences microbial prevalence, there may be multiple mechanisms causing such effects that may also depend on the foraging strategy of the microbes. We employed a natural gradient of rodent‐species richness to examine competing hypotheses describing possible mechanisms mediating the relationship between host‐species richness and the prevalence of the most dominant microbes, along with microbe specificity to the different rodent host species. We sampled blood from three gerbil species in plots differing in terms of the proportion of the different species and screened for the most dominant bacteria. Two dominant bacterial lineages were detected: host‐specific bacteria and host‐opportunistic bacteria. Using a model selection approach, we detected evidence for both direct and indirect effects of host‐species richness on the prevalence of these bacteria. Infection probability of the host‐specific lineage was lower in richer host communities, most likely due to increased frequency and density of the least suitable host species. In contrast, field observations suggest that the effect of host‐species richness on infection probability of the opportunistic lineage was both direct and indirect, mostly mediated by changes in flea densities on the host and by the presence of the host‐specific lineage. Our results thus suggest that host‐species richness has multiple effects on microbial prevalence, depending on the degree of host‐specificity of the microbe in question.
    Keywords: Co-Infection ; Dilution Effect ; Flea-Borne Bacteria ; Host Specificity ; Natural Field Experiment ; Species Diversity ; Species Richness
    ISSN: 0012-9658
    E-ISSN: 1939-9170
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  • 6
    Language: English
    In: Oecologia, 2007, Vol.154(3), pp.601-609
    Description: Mechanisms that cause nonrandom patterns of parasite distribution among host individuals may influence the population and evolutionary dynamics of both parasites and hosts, but are still poorly understood. We studied whether survival, reproduction, and behavioral responses of fleas ( Xenopsylla conformis ) changed with the age of their rodent hosts ( Meriones crassus ), experimentally disentangling two possible mechanisms: (a) differential survival and/or fitness reward of parasites due to host age, and (b) active parasite choice of a host of a particular age. To explore the first mechanism, we raised fleas on rodents of two age groups and assessed flea survival as well as the quantity and quality of their offspring. To explore the second mechanism, three groups of fleas that differed in their previous feeding experience (no experience, experience on juvenile or experience on adult rodents) were given an opportunity to choose between juvenile and adult rodents in a Y-maze. Fleas raised on juvenile rodents had higher survival and had more offspring that emerged earlier than fleas raised on adults. However, fleas did not show any innate preference for juvenile rodents, nor were they able to learn to choose them. In contrast to our predictions, based on a single previous exposure, fleas learned to choose adult rodents. The results suggest that two mechanisms—differential survival and fitness reward of fleas, and associative learning by them—affect patterns of flea distribution between juvenile and adult rodents. The former increases whereas the latter reduces flea densities on juvenile rodents. The ability of fleas to learn to choose adult but not juvenile hosts may be due to: (a) a stronger stimulus from adults, (b) a higher profitability of adults in terms of predictability and abundance, or (c) the evolutionary importance of recognizing adult but not juvenile hosts as representatives of the species.
    Keywords: Host choice ; Learning ; Distribution among host individuals ; Fitness reward ; Rodents
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 7
    Language: English
    In: The American Naturalist March 2010, Vol.175(3), pp.374-381
    Description: Abstract: An individual behaves spitefully when it harms itself in the act of harming other individuals. One of the clearest potential examples of spite is the costly production and release of toxins called bacteriocins. Bacteriocins are toxins produced by bacteria that can kill closely related strains of the same species. Theoretical work has predicted that bacteriocin‐mediated interactions could play an important role in maintaining local genetic and/or species diversity, but these interactions have not been studied at biologically relevant scales in nature. Here we studied toxin production and among‐strain inhibitions in a natural population of Xenorhabdus bovienii . We found genetic differences and inhibitions between colonies that were collected only a few meters apart. These results suggest that spite exists in natural populations of bacteria.
    Keywords: Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Biology -- Microbiology ; Physical sciences -- Chemistry -- Chemical compounds ; Biological sciences -- Ecology -- Animal ecology ; Biological sciences -- Biology -- Microbiology ; Biological sciences -- Biochemistry -- Biomolecules ; Biological sciences -- Biology -- Zoology ; Applied sciences -- Laboratory techniques -- Nucleic acid amplification techniques ; Biological sciences -- Biology -- Zoology ; Biological sciences -- Biology -- Cytology ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Biology -- Microbiology ; Physical sciences -- Chemistry -- Chemical compounds ; Biological sciences -- Ecology -- Animal ecology ; Biological sciences -- Biology -- Microbiology ; Biological sciences -- Biochemistry -- Biomolecules ; Biological sciences -- Biology -- Zoology ; Applied sciences -- Laboratory techniques -- Nucleic acid amplification techniques ; Biological sciences -- Biology -- Zoology ; Biological sciences -- Biology -- Cytology;
    ISSN: 00030147
    E-ISSN: 15375323
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  • 8
    In: Molecular Ecology, September 2018, Vol.27(18), pp.3714-3726
    Description: The way that some parasites and pathogens persist in the hostile environment of their host for long periods remains to be resolved. Here, longitudinal field surveys were combined with laboratory experiments to investigate the routes of transmission and infection dynamics of such a pathogen—a wild rodent haemotropic bacterium, specifically a ‐like bacterium. Fleaborne transmission, direct rodent‐to‐rodent transmission and vertical transmission from fleas or rodents to their offspring were experimentally quantified, and indications were found that the main route of bacterial transmission is direct, although its rate of successful transmission is low (~20%). The bacterium's temporal dynamics was then compared in the field to that observed under a controlled infection experiment in field‐infected and laboratory‐infected rodents, and indications were found, under all conditions, that the bacterium reached its peak infection level after 25–45 days and then decreased to low bacterial loads, which persist for the rodent's lifetime. These findings suggest that the bacterium relies on persistency with low bacterial loads for long‐term coexistence with its rodent host, having both conceptual and applied implications.
    Keywords: Haemoplasmas ; Haemotropic Mycoplasmas ; Host–Parasite Interactions ; Infection Dynamics ; Persistent Infection ; Transmission Mechanisms ; Wild Rodent
    ISSN: 0962-1083
    E-ISSN: 1365-294X
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  • 9
    Language: English
    In: Parasites & vectors, 19 August 2015, Vol.8, pp.429
    Description: The parasite composition of wild host individuals often impacts their behavior and physiology, and the transmission dynamics of pathogenic species thereby determines disease risk in natural communities. Yet, the determinants of parasite composition in natural communities are still obscure. In particular, three fundamental questions remain open: (1) what are the relative roles of host and environmental characteristics compared with direct interactions between parasites in determining the community composition of parasites? (2) do these determinants affect parasites belonging to the same guild and those belonging to different guilds in similar manners? and (3) can cross-sectional and longitudinal analyses work interchangeably in detecting community determinants? Our study was designed to answer these three questions in a natural community of rodents and their fleas, ticks, and two vector-borne bacteria. We sampled a natural population of Gerbillus andersoni rodents and their blood-associated parasites on two occasions. By combining path analysis and model selection approaches, we then explored multiple direct and indirect paths that connect (i) the environmental and host-related characteristics to the infection probability of a host by each of the four parasite species, and (ii) the infection probabilities of the four species by each other. Our results suggest that the majority of paths shaping the blood-associated communities are indirect, mostly determined by host characteristics and not by interspecific interactions or environmental conditions. The exact effects of host characteristics on infection probability by a given parasite depend on its life history and on the method of sampling, in which the cross-sectional and longitudinal methods are complementary. Despite the awareness of the need of ecological investigations into natural host-vector-parasite communities in light of the emergence and re-emergence of vector-borne diseases, we lack sampling methods that are both practical and reliable. Here we illustrated how comprehensive patterns can be revealed from observational data by applying path analysis and model selection approaches and combining cross-sectional and longitudinal analyses. By employing this combined approach on blood-associated parasites, we were able to distinguish between direct and indirect effects and to predict the causal relationships between host-related characteristics and the parasite composition over time and space. We concluded that direct interactions within the community play only a minor role in determining community composition relative to host characteristics and the life history of the community members.
    Keywords: Ecosystem ; Host-Parasite Interactions ; Bacteria -- Isolation & Purification ; Gerbillinae -- Microbiology ; Siphonaptera -- Growth & Development ; Ticks -- Growth & Development
    E-ISSN: 1756-3305
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  • 10
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(10), p.e109677
    Description: Relationships between host and microbial diversity have important ecological and applied implications. Theory predicts that these relationships will depend on the spatio-temporal scale of the analysis and the niche breadth of the organisms in question, but representative data on host-microbial community assemblage in nature is lacking. We employed a natural gradient of rodent species richness and quantified bacterial communities in rodent blood at several hierarchical spatial scales to test the hypothesis that associations between host and microbial species diversity will be positive in communities dominated by organisms with broad niches sampled at large scales. Following pyrosequencing of rodent blood samples, bacterial communities were found to be comprised primarily of broad niche lineages. These communities exhibited positive correlations between host diversity, microbial diversity and the likelihood for rare pathogens at the regional scale but not at finer scales. These findings demonstrate how microbial diversity is affected by host diversity at different spatial scales and suggest that the relationships between host diversity and overall disease risk are not always negative, as the dilution hypothesis predicts.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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