scholarly journals Modeling host-associating microbes under selection

2021 ◽  
Author(s):  
Florence Bansept ◽  
Nancy Obeng ◽  
Hinrich Schulenburg ◽  
Arne Traulsen
Keyword(s):  
Life Cycle ◽  
Microbial Population ◽  
Initial Distribution ◽  
Life Cycles ◽  
Phenotypic Traits ◽  
Complex Life Cycles ◽  
Selection Gradient ◽  
Migration Rates ◽  
Intensity Of Competition ◽  
Global Growth

The concept of fitness is often reduced to a single component, such as the replication rate in a given habitat. For species with complex life cycles, this can be an unjustified oversimplification, as every step of the life cycle can contribute to reproductive success in a specific way. In particular, this applies to microbes that spend part of their life cycles associated to a host, i.e. in a microbiota. In this case, there is a selection pressure not only on the replication rates, but also on the phenotypic traits associated to migrating from the external environment to the host and vice-versa. Here, we investigate a simple model of a microbial population living, replicating, migrating and competing in and between two compartments: a host and its environment. We perform a sensitivity analysis on the global growth rate to determine the selection gradient experienced by the microbial population. We focus on the direction of selection at each point of the phenotypic space, defining an optimal way for the microbial population to increase its fitness. We show that microbes can adapt to the two-compartment life cycle through either changes in replication or migration rates, depending on the initial values of the traits, the initial distribution of the population across the compartments, the intensity of competition, and the time scales involved in the life cycle versus the time scale of adaptation (which determines the adequate probing time to measure fitness). Overall, our model provides a conceptual framework to study the selection on microbes experiencing a host-associated life cycle.

scholarly journals Modeling host-associating microbes under selection

2021 ◽  
Author(s):  
Florence Bansept ◽  
Nancy Obeng ◽  
Hinrich Schulenburg ◽  
Arne Traulsen
Keyword(s):  
Life Cycle ◽  
Selection Pressure ◽  
External Environment ◽  
Initial Distribution ◽  
Life Cycles ◽  
Phenotypic Traits ◽  
Replication Rate ◽  
Selection Gradient ◽  
Migration Rates ◽  
Intensity Of Competition

AbstractThe concept of fitness is often reduced to a single component, such as the replication rate in a given habitat. For species with multi-step life cycles, this can be an unjustified oversimplification, as every step of the life cycle can contribute to the overall reproductive success in a specific way. In particular, this applies to microbes that spend part of their life cycles associated to a host. In this case, there is a selection pressure not only on the replication rates, but also on the phenotypic traits associated to migrating from the external environment to the host and vice-versa (i.e., the migration rates). Here, we investigate a simple model of a microbial lineage living, replicating, migrating and competing in and between two compartments: a host and an environment. We perform a sensitivity analysis on the overall growth rate to determine the selection gradient experienced by the microbial lineage. We focus on the direction of selection at each point of the phenotypic space, defining an optimal way for the microbial lineage to increase its fitness. We show that microbes can adapt to the two-compartment life cycle through either changes in replication or migration rates, depending on the initial values of the traits, the initial distribution across the two compartments, the intensity of competition, and the time scales involved in the life cycle versus the time scale of adaptation (which determines the adequate probing time to measure fitness). Overall, our model provides a conceptual framework to study the selection on microbes experiencing a host-associated life cycle.

Autonomy and integration in complex parasite life cycles

Parasitology ◽  
2016 ◽  
Vol 143 (14) ◽  
pp. 1824-1846 ◽  
Author(s):  
DANIEL P. BENESH
Keyword(s):  
Life Cycle ◽  
Holistic Approach ◽  
Life Cycles ◽  
Complex Life Cycle ◽  
Functional Specialization ◽  
Life Stages ◽  
Free Living ◽  
New Host ◽  
Complex Life Cycles ◽  
Life Cycle Stages

SUMMARYComplex life cycles are common in free-living and parasitic organisms alike. The adaptive decoupling hypothesis postulates that separate life cycle stages have a degree of developmental and genetic autonomy, allowing them to be independently optimized for dissimilar, competing tasks. That is, complex life cycles evolved to facilitate functional specialization. Here, I review the connections between the different stages in parasite life cycles. I first examine evolutionary connections between life stages, such as the genetic coupling of parasite performance in consecutive hosts, the interspecific correlations between traits expressed in different hosts, and the developmental and functional obstacles to stage loss. Then, I evaluate how environmental factors link life stages through carryover effects, where stressful larval conditions impact parasites even after transmission to a new host. There is evidence for both autonomy and integration across stages, so the relevant question becomes how integrated are parasite life cycles and through what mechanisms? By highlighting how genetics, development, selection and the environment can lead to interdependencies among successive life stages, I wish to promote a holistic approach to studying complex life cycle parasites and emphasize that what happens in one stage is potentially highly relevant for later stages.

Life Cycles

2001 ◽  
Author(s):  
Jan A. Pechenik
Keyword(s):  
Life Cycle ◽  
Genetic Material ◽  
Life Cycles ◽  
Offspring Size ◽  
Free Living ◽  
Complex Life Cycles ◽  
Volume Number ◽  
Larval Stages ◽  
Underlying Mechanisms ◽  
Life Cycle Evolution

I have a Hardin cartoon on my office door. It shows a series of animals thinking about the meaning of life. In sequence, we see a lobe-finned fish, a salamander, a lizard, and a monkey, all thinking, “Eat, survive, reproduce; eat, survive, reproduce.” Then comes man: “What's it all about?” he wonders. Organisms live to reproduce. The ultimate selective pressure on any organism is to survive long enough and well enough to pass genetic material to a next generation that will also be successful in reproducing. In this sense, then, every morphological, physiological, biochemical, or behavioral adaptation contributes to reproductive success, making the field of life cycle evolution a very broad one indeed. Key components include mode of sexuality, age and size at first reproduction (Roff, this volume), number of reproductive episodes in a lifetime, offspring size (Messina and Fox, this volume), fecundity, the extent to which parents protect their offspring and how that protection is achieved, source of nutrition during development, survival to maturity, the consequences of shifts in any of these components, and the underlying mechanisms responsible for such shifts. Many of these issues are dealt with in other chapters. Here I focus exclusively on animals, and on a particularly widespread sort of life cycle that includes at least two ecologically distinct free-living stages. Such “complex life cycles” (Istock 1967) are especially common among amphibians and fishes (Hall and Wake 1999), and within most invertebrate groups, including insects (Gilbert and Frieden 1981), crustaceans, bivalves, gastropods, polychaete worms, echinoderms, bryozoans, and corals and other cnidarians (Thorson 1950). In such life cycles, the juvenile or adult stage is reached by metamorphosing from a preceding, free-living larval stage. In many species, metamorphosis involves a veritable revolution in morphology, ecology, behavior, and physiology, sometimes taking place in as little as a few minutes or a few hours. In addition to the issues already mentioned, key components of such complex life cycles include the timing of metamorphosis (i.e., when it occurs), the size at which larvae metamorphose, and the consequences of metamorphosing at particular times or at particular sizes. The potential advantages of including larval stages in the life history have been much discussed.

Detection of a new Clytia species (Cnidaria: Hydrozoa: Campanulariidae) with DNA barcoding and life cycle analyses

2013 ◽  
Vol 93 (8) ◽  
pp. 2075-2088 ◽  
Author(s):  
Konglin Zhou ◽  
Lianming Zheng ◽  
Jinru He ◽  
Yuanshao Lin ◽  
Wenqing Cao ◽  
...  
Keyword(s):  
Life Cycle ◽  
Dna Barcoding ◽  
Ribosomal Rna ◽  
Coastal Waters ◽  
Large Subunit ◽  
Life Cycles ◽  
Complex Life Cycles ◽  
Distinct Lineage ◽  
Whole Life Cycle ◽  
Medusa Stage

The genus Clytia is distributed worldwide, but most accepted species in this genus have been examined either only at the hydroid or medusa stage. The challenge in identifying Clytia species reflects their complex life cycles and phenotypic plasticity. In this study, molecular and morphological investigations of Clytia specimens from the coastal waters of China revealed an as yet unreported species, designated C. xiamenensis sp. nov., that was considered as conspecific to two nearly cosmopolitan species, C. hemisphaerica and C. gracilis. DNA barcoding based on partial mitochondrial cytochrome c oxidase subunit I (COI) and large subunit ribosomal RNA gene (16S) confirmed the highly distinct lineage of C. xiamenensis sp. nov. These results were corroborated by the detailed observations of its mature medusae and its colonies, which showed that C. xiamenensis sp. nov. was morphologically distinct from other species of Clytia. Thus, based on our findings, the nearly cosmopolitan distribution attributed to some species of Clytia might rather be due to the misidentification, and it is necessary to elucidate their whole life cycle in order to establish the systematic validity of all species within the genus Clytia.

The diversity and natural history of parasites

2021 ◽  
pp. 19-50
Author(s):  
Paul Schmid-Hempel
Keyword(s):  
Life Cycle ◽  
Natural History ◽  
Food Chain ◽  
Life Cycles ◽  
Growth Phases ◽  
New Host ◽  
Complex Life Cycles ◽  
Parasitic Species ◽  
Parasitic Lifestyle ◽  
History Of

Parasites are more numerous than non-parasitic species and have evolved in virtually all groups of organisms, such as viruses, prokaryotes (bacteria), protozoa, fungi, nematodes, flatworms, acantocephalans, annelids, crustaceans, and arthropods (crustacea, mites, ticks, insects). These groups have adapted to the parasitic lifestyle in very many ways. Evolution towards parasitism has also followed different routes. Initial steps such as phoresy, followed by later consumption of the transport host, are plausible evolutionary routes. Alternatively, formerly free-living forms have become commensals before evolving parasitism. Complex life cycles with several hosts evolved by scenarios such as upward (adding a new host upwards in the food chain), downward, or lateral incorporation, driven by the advantage of extending growth phases within hosts and increasing fecundity. Examples are digenea; other parasites have added vectors to their life cycle.

Identification of life cycle stages of the nematode Echinocephalus overstreeti by allozyme electrophoresis

1988 ◽  
Vol 62 (2) ◽  
pp. 153-157 ◽  
Author(s):  
R. H. Andrews ◽  
I. Beveridge ◽  
M. Adams ◽  
P. R. Baverstock
Keyword(s):  
Life Cycle ◽  
Electrophoretic Analysis ◽  
Life Cycles ◽  
Allozyme Electrophoresis ◽  
Larval Form ◽  
Complex Life Cycles ◽  
Life Cycle Stages ◽  
Allelic Differences ◽  
Mollusc Species ◽  
Shared Alleles

ABSTRACTData presented in this study highlight the potential of allozyme electrophoresis in providing unequivocal genetic evidence for the identification of life cycle stages, particularly where species have complex life cycles. Adults of the nematode Echinocephalus overstreeti parasitize the elasmobranch Heterodontus portusjacksoni. The putative larval form which is morphologically dissimilar is found in two species of marine molluscs, Chlamys bifrons and Pecten albus. Electrophoretic analysis indicated that the adult and larval forms shared alleles at all of the 34 enzyme loci established. Furthermore, there were no fixed allelic differences between larval forms from different mollusc species.

scholarly journals Developmental plasticity and the evolution of animal complex life cycles

2010 ◽  
Vol 365 (1540) ◽  
pp. 631-640 ◽  
Author(s):  
Alessandro Minelli ◽  
Giuseppe Fusco
Keyword(s):  
Life Cycle ◽  
Developmental Plasticity ◽  
Developmental Stages ◽  
Ecological Condition ◽  
Life Cycles ◽  
Complex Life Cycle ◽  
Complex Life Cycles ◽  
Transcription Profiles ◽  
Alternative Phenotypes ◽  
Reproductive Events

Metazoan life cycles can be complex in different ways. A number of diverse phenotypes and reproductive events can sequentially occur along the cycle, and at certain stages a variety of developmental and reproductive options can be available to the animal, the choice among which depends on a combination of organismal and environmental conditions. We hypothesize that a diversity of phenotypes arranged in developmental sequence throughout an animal's life cycle may have evolved by genetic assimilation of alternative phenotypes originally triggered by environmental cues. This is supported by similarities between the developmental mechanisms mediating phenotype change and alternative phenotype determination during ontogeny and the common ecological condition that favour both forms of phenotypic variation. The comparison of transcription profiles from different developmental stages throughout a complex life cycle with those from alternative phenotypes in closely related polyphenic animals is expected to offer critical evidence upon which to evaluate our hypothesis.

LIFE CYCLE PATHWAYS AND THE ANALYSIS OF COMPLEX LIFE CYCLES IN INSECTS

1991 ◽  
Vol 123 (1) ◽  
pp. 23-40 ◽  
Author(s):  
H.V. Danks
Keyword(s):  
Life Cycle ◽  
Life Cycles ◽  
Complex Life Cycle ◽  
Temporal Control ◽  
Complex Life Cycles ◽  
Environmental Controls ◽  
Decision Points ◽  
Flow Charts ◽  
Life Cycle Patterns ◽  
Simple Life

AbstractThe structure and temporal control of insect life cycles can best be understood by viewing them as pathways along which various options (e.g. develop or enter diapause; grow rapidly or grow slowly) are chosen in response to environmental controls such as photoperiod and temperature. Simple life cycles include small numbers of such options. The combination of several successive simple elements, however, can produce remarkably complex life cycle patterns, which are more prevalent than most entomologists have recognized. The ways in which these simple elements contribute to life cycle pathways are outlined and illustrated schematically. Flow charts showing the successive decision points in the life cycle then are constructed for selected species. This approach confirms the different simple elements, and shows how they are used in combination to control seasonal life cycles in nature.

Coordination of the Cell Cycle in Trypanosomes

2019 ◽  
Vol 73 (1) ◽  
pp. 133-154 ◽  
Author(s):  
Richard J. Wheeler ◽  
Keith Gull ◽  
Jack D. Sunter
Keyword(s):  
Cell Cycle ◽  
Life Cycle ◽  
Trypanosoma Brucei ◽  
Cross Talk ◽  
Life Cycle Stage ◽  
Life Cycles ◽  
Complex Life Cycles ◽  
Cell Divisions ◽  
Proliferative Cell

Trypanosomes have complex life cycles within which there are both proliferative and differentiation cell divisions. The coordination of the cell cycle to achieve these different divisions is critical for the parasite to infect both host and vector. From studying the regulation of the proliferative cell cycle of the Trypanosoma brucei procyclic life cycle stage, three subcycles emerge that control the duplication and segregation of ( a) the nucleus, ( b) the kinetoplast, and ( c) a set of cytoskeletal structures. We discuss how the clear dependency relationships within these subcycles, and the potential for cross talk between them, are likely required for overall cell cycle coordination. Finally, we look at the implications this interdependence has for proliferative and differentiation divisions through the T. brucei life cycle and in related parasitic trypanosomatid species.

scholarly journals Major host transitions are modulated through transcriptome-wide reprograming events in Schistocephalus solidus, a threespine stickleback parasite

2016 ◽  
Author(s):  
François Olivier Hébert ◽  
Stephan Grambauer ◽  
Iain Barber ◽  
Christian R Landry ◽  
Nadia Aubin-Horth
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Final Host ◽  
Life Cycles ◽  
Threespine Stickleback ◽  
Complex Life Cycle ◽  
Ecological Niches ◽  
Avian Host ◽  
Complex Life Cycles ◽  
Schistocephalus Solidus

ABSTRACTParasites with complex life cycles have developed numerous phenotypic strategies, closely associated with developmental events, to enable the exploitation of different ecological niches and facilitate transmission between hosts. How these environmental shifts are regulated from a metabolic and physiological standpoint, however, still remain to be fully elucidated. We examined the transcriptomic response of Schistocephalus solidus, a trophically-transmitted parasite with a complex life cycle, over the course of its development in an intermediate host, the threespine stickleback, and the final avian host. Results from our differential gene expression analysis show major reprogramming events among developmental stages. The final host stage is characterized by a strong activation of reproductive pathways and redox homeostasis. The attainment of infectivity in the fish intermediate host – which precedes sexual maturation in the final host and is associated with host behaviour changes – is marked by transcription of genes involved in neural pathways and sensory perception. Our results suggest that un-annotated and S. solidus-specific genes could play a determinant role in host-parasite molecular interactions required to complete the parasite’s life cycle. Our results permit future comparative analyses to help disentangle species-specific patterns of infection from conserved mechanisms, ultimately leading to a better understanding of the molecular control and evolution of complex life cycles.

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