scholarly journals Skin-penetrating nematodes exhibit life-stage-specific interactions with host-associated and environmental bacteria

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Ivan N. Chavez ◽  
Taylor M. Brown ◽  
Adrien Assié ◽  
Astra S. Bryant ◽  
Buck S. Samuel ◽  
...  
Keyword(s):  
Life Cycle ◽  
Life Stage ◽  
Behavioral Responses ◽  
Strongyloides Stercoralis ◽  
Amplicon Sequencing ◽  
Ecological Niches ◽  
Free Living ◽  
Egg Hatching ◽  
Host Seeking ◽  
Environmental Bacteria

Abstract Background Skin-penetrating nematodes of the genus Strongyloides infect over 600 million people, posing a major global health burden. Their life cycle includes both a parasitic and free-living generation. During the parasitic generation, infective third-stage larvae (iL3s) actively engage in host seeking. During the free-living generation, the nematodes develop and reproduce on host feces. At different points during their life cycle, Strongyloides species encounter a wide variety of host-associated and environmental bacteria. However, the microbiome associated with Strongyloides species, and the behavioral and physiological interactions between Strongyloides species and bacteria, remain unclear. Results We first investigated the microbiome of the human parasite Strongyloides stercoralis using 16S-based amplicon sequencing. We found that S. stercoralis free-living adults have an associated microbiome consisting of specific fecal bacteria. We then investigated the behavioral responses of S. stercoralis and the closely related rat parasite Strongyloides ratti to an ecologically diverse panel of bacteria. We found that S. stercoralis and S. ratti showed similar responses to bacteria. The responses of both nematodes to bacteria varied dramatically across life stages: free-living adults were strongly attracted to most of the bacteria tested, while iL3s were attracted specifically to a narrow range of environmental bacteria. The behavioral responses to bacteria were dynamic, consisting of distinct short- and long-term behaviors. Finally, a comparison of the growth and reproduction of S. stercoralis free-living adults on different bacteria revealed that the bacterium Proteus mirabilis inhibits S. stercoralis egg hatching, and thereby greatly decreases parasite viability. Conclusions Skin-penetrating nematodes encounter bacteria from various ecological niches throughout their life cycle. Our results demonstrate that bacteria function as key chemosensory cues for directing parasite movement in a life-stage-specific manner. Some bacterial genera may form essential associations with the nematodes, while others are detrimental and serve as a potential source of novel nematicides.

scholarly journals Nematode Hsp90: highly conserved but functionally diverse

Parasitology ◽  
2014 ◽  
Vol 141 (9) ◽  
pp. 1203-1215 ◽  
Author(s):  
VICTORIA GILLAN ◽  
EILEEN DEVANEY
Keyword(s):  
Life Cycle ◽  
Heat Shock Protein 90 ◽  
Ecological Niches ◽  
Actual Number ◽  
Host Organism ◽  
Free Living ◽  
Parasitic Species ◽  
Free Living Nematode ◽  
Functionally Diverse

SUMMARYNematodes are amongst the most successful and abundant organisms on the planet with approximately 30 000 species described, although the actual number of species is estimated to be one million or more. Despite sharing a relatively simple and invariant body plan, there is considerable diversity within the phylum. Nematodes have evolved to colonize most ecological niches, and can be free-living or can parasitize plants or animals to the detriment of the host organism. In this review we consider the role of heat shock protein 90 (Hsp90) in the nematode life cycle. We describe studies on Hsp90 in the free-living nematode Caenorhabditis elegans and comparative work on the parasitic species Brugia pahangi, and consider whether a dependence upon Hsp90 can be exploited for the control of parasitic species.

scholarly journals Chemosensory mechanisms of host seeking and infectivity in skin-penetrating nematodes

2020 ◽  
Vol 117 (30) ◽  
pp. 17913-17923 ◽  
Author(s):  
Spencer S. Gang ◽  
Michelle L. Castelletto ◽  
Emily Yang ◽  
Felicitas Ruiz ◽  
Taylor M. Brown ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Strongyloides Stercoralis ◽  
Sensory Cues ◽  
Ancylostoma Ceylanicum ◽  
Free Living ◽  
Infective Larvae ◽  
Host Seeking ◽  
Third Stage ◽  
Olfactory Preferences ◽  
Insight Into

Approximately 800 million people worldwide are infected with one or more species of skin-penetrating nematodes. These parasites persist in the environment as developmentally arrested third-stage infective larvae (iL3s) that navigate toward host-emitted cues, contact host skin, and penetrate the skin. iL3s then reinitiate development inside the host in response to sensory cues, a process called activation. Here, we investigate how chemosensation drives host seeking and activation in skin-penetrating nematodes. We show that the olfactory preferences of iL3s are categorically different from those of free-living adults, which may restrict host seeking to iL3s. The human-parasitic threadwormStrongyloides stercoralisand hookwormAncylostoma ceylanicumhave highly dissimilar olfactory preferences, suggesting that these two species may use distinct strategies to target humans. CRISPR/Cas9-mediated mutagenesis of theS. stercoralis tax-4gene abolishes iL3 attraction to a host-emitted odorant and prevents activation. Our results suggest an important role for chemosensation in iL3 host seeking and infectivity and provide insight into the molecular mechanisms that underlie these processes.

scholarly journals The neural basis of temperature-driven host seeking in the human threadworm Strongyloides stercoralis

2021 ◽  
Author(s):  
Astra S Bryant ◽  
Felicitas Ruiz ◽  
Joon Ha Lee ◽  
Elissa A Hallem
Keyword(s):  
Human Body ◽  
Direct Evidence ◽  
Strongyloides Stercoralis ◽  
Parasitic Nematodes ◽  
Body Temperatures ◽  
Neural Basis ◽  
Free Living ◽  
Host Seeking ◽  
Coding Strategies ◽  
Human Body Temperature

Soil-transmitted parasitic nematodes infect approximately one billion people and are a major cause of morbidity worldwide. The infective larvae (iL3s) of these parasites actively search for hosts in a poorly understood, sensory-driven process that requires thermal cues. Here, we describe the neural basis of temperature-driven host seeking in parasitic nematodes using the human threadworm Strongyloides stercoralis. We show that S. stercoralis thermosensation is mediated by the AFD neurons, a thermosensory neuron class that is conserved between parasitic and free-living nematodes. We demonstrate that S. stercoralis AFD displays parasite-specific adaptations that enable both nonlinear and linear encoding of temperatures up to human body temperature. Furthermore, we describe a novel thermosensory behavior in which S. stercoralis iL3s generate spontaneous reversals of temperature preference at below-body temperatures. Finally, we identify three thermoreceptors selectively expressed in S. stercoralis AFD that display parasite-specific sensitivities to human body temperatures and likely enable temperature-driven host seeking by iL3s. Our results are the first direct evidence that the sensory neurons of soil-transmitted parasitic nematodes exhibit parasite-specific neural adaptations and sensory coding strategies that allow them to target human hosts, a finding with important implications for efforts to develop new therapeutic strategies for nematode control.

scholarly journals Modulation of odour-guided behaviour in mosquitoes

2021 ◽  
Vol 383 (1) ◽  
pp. 195-206
Author(s):  
Sharon R. Hill ◽  
Rickard Ignell
Keyword(s):  
Functional Genomics ◽  
Life Stage ◽  
Blood Feeding ◽  
Model Systems ◽  
Extrinsic Factors ◽  
Intrinsic Factors ◽  
Host Seeking ◽  
Enhancing Resources ◽  
Maturation Age ◽  
Behavioural Repertoire

AbstractMosquitoes are emerging as model systems with which to study innate behaviours through neuroethology and functional genomics. Decades of work on these disease vectors have provided a solid behavioural framework describing the distinct repertoire of predominantly odour-mediated behaviours of female mosquitoes, and their dependence on life stage (intrinsic factors) and environmental cues (extrinsic factors). The purpose of this review is to provide an overview of how intrinsic factors, including adult maturation, age, nutritional status, and infection, affect the attraction to plants and feeding on plant fluids, host seeking, blood feeding, supplemental feeding behaviours, pre-oviposition behaviour, and oviposition in female mosquitoes. With the technological advancements in the recent two decades, we have gained a better understanding of which volatile organic compounds are used by mosquitoes to recognise and discriminate among various fitness-enhancing resources, and characterised their neural and molecular correlates. In this review, we present the state of the art of the peripheral olfactory system as described by the neural physiology, functional genomics, and genetics underlying the demonstrated changes in the behavioural repertoire in female mosquitoes. The review is meant as a summary introduction to the current conceptual thinking in the field.

Field studies on the behaviour of bird fleas

Parasitology ◽  
1962 ◽  
Vol 52 (1-2) ◽  
pp. 113-132 ◽  
Author(s):  
John Keith Bates ◽  
Miriam Rothschild
Keyword(s):  
Field Studies ◽  
Nest Material ◽  
Breeding Area ◽  
Free Living ◽  
Host Seeking ◽  
Feeding Area ◽  
Sand Martin ◽  
Adult Flea

1. Factors controlling the distribution of the bird fleas Ceratophyllus styx, the sand-martin flea, C. gallinae, the hen flea, and Dasypsylla gallinulae, the blackbird flea, were investigated in the field.2. Sand-martin fleas (C. styx) pass the winter as adults within cocoons in the old nests of their host. Observations indicate that the fleas are stimulated to emerge from the cocoons by the rise in temperature in the spring, and some of the adult fleas emigrate in the spring and invade new nest burrows. Observations and experiments showed that sand-martin fleas disperse from old burrows both laterally and vertically and that emigrating fleas could reach areas as far as 33·8 m. from the old nests. The detection of the new burrow entrances is not due to vision, or to the recognition of difference of humidity between the burrow and the cliff face, or to the reaction to air current differences between the burrow and the cliff face, but to recognition of the horizontal floor of the burrows and a tendency to congregate upon horizontal surfaces. How the fleas distinguish the horizontal burrow surface from the cliff top is still unknown. The colonization of new burrows by the fleas does not occur at night. It is suggested that, in addition to finding their hosts in the spring by invading new burrows, sand-martin fleas may jump on to the birds when they are hovering near the cliff face. Many adult fleas leave the burrows within 3 days of the fledging time of the young sand-martins but a small number remain within the nest. The fate of these specimens is not known.3. C. gallinae, the hen flea, and D. gallinulae, the blackbird flea, pass the winter principally as adults enclosed in the cocoons in the old nest material. In the spring they emerge from the cocoons, emigrate away from the old nest and are free-living on the ground. Probably the adult C. gallinae and D. gallinulae jump on to birds when they are feeding on the ground in the spring.* Therefore the absence of hen fleas in nests situated on the ground or in open nests built in low vegetation, is not due to lack of opportunity of contact between the adult flea and the birds which construct such nests.4. It is concluded that in host-seeking, adults of C. gallinae and D. gallinulae emigrate away from old nests in the spring and come in contact with the host birds on the ground in the birds' feeding area, whereas C. styx adults emigrate into the hosts' breeding area and come in contact with the birds in the new nesting burrows.

Observing microscopic phases of lichen life cycles on transparent substrata placed in situ

2005 ◽  
Vol 37 (5) ◽  
pp. 373-382 ◽  
Author(s):  
William B. SANDERS
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Life Cycles ◽  
Potential Significance ◽  
Free Living ◽  
Lichen Community ◽  
One Year ◽  
The One ◽  
Observation Period

The utility of plastic cover slips as a substratum for in situ study of lichen developmental stages is further explored in a neotropical foliicolous lichen community and in a European temperate corticolous community. Twenty-one months after placement in the tropical forest, the cover slips bore foliicolous lichen thalli with several species producing characteristic ascocarps and ascospores, indicating the suitability of the substratum for completion of the life cycle of these lichens. On cover slips placed within the temperate corticolous community, lichen propagules anchored to the substratum with relatively short attachment hyphae but did not develop further within the one year observation period. Intimately intermixed microbial communities of short-celled, mainly pigmented fungi and chlorophyte algae developed upon the transparent substratum. Among the algae, Trebouxia cells, often in groups showing cell division and without associated lichenizing hyphae, were commonly observed. The potential significance of the free-living populations in the life cycle of Trebouxia and in those of Trebouxia-associated lichen fungi is discussed.

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.

Observation of the Free-living Adults of Strongyloides stercoralis from a Human Stool in Korea

2009 ◽  
Vol 41 (2) ◽  
pp. 105 ◽  
Author(s):  
Young-Hee Hong ◽  
Jong-Wan Kim ◽  
In-Soo Rheem ◽  
Jae-Soo Kim ◽  
Suk-Bae Kim ◽  
...  
Keyword(s):  
Strongyloides Stercoralis ◽  
Free Living ◽  
Human Stool

Memoirs: An Account of Amoeba Discoides; its Culture and Life History

1938 ◽  
Vol s2-80 (319) ◽  
pp. 459-478
Author(s):  
CATHERINE HAYES
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Amoeba Proteus ◽  
Tropical Fish ◽  
Free Living ◽  
Free Living Amoeba ◽  
College Laboratory ◽  
Petri Dishes ◽  
Fish Tanks

1. A large free-living amoeba found by Mr. Harry Watkinson in the tropical fish tanks of Mr. Albert Sutcliffe of Grimsby has been identified as Amoeba discoides (Schaeffer, 1916) = Metachaos discoides (Schaeffer, 1926). 2. From the inoculation material obtained from these tanks Amoeba discoides has been successfully cultivated in the Notre Dame Training College Laboratory by a technique similar to that used for the cultivation of Amoeba proteus: wheat being the pabulum employed. In contrast to what obtains in the cultivation of Amoeba proteus , however, Amoeba discoides flourishes more luxuriantly in shallow Petri dishes, than in deeper troughs. 3. The nucleus in the resting and dividing stages is described; division is amitotic. 4. The more important cytoplasmic contents, including nutritive spheres, and crystals are likewise described. 5. The life-history has been worked out. The adult amoeba becomes an agamont giving rise to agametes which eventually grow into adult amoebae, the life-cycle occupying roughly about four months. 6. Descriptions of the nucleus of the newly hatched and developing amoebae are deferred. I wish to offer my sincerest thanks to Professor Graham Kerr under whom this work was begun, and who has continued from afar to watch over it with ever kindly interest and encouragement and who has read the paper in typescript. My thanks are also extended to Professor Hindle, under whom the work was completed, for his kind advice and for reading the paper in typescript. In conclusion I would like to express my appreciation of her skill and of the care and trouble bestowed by Miss Brown Kelly in the execution of the original drawing of fig. 1, PI. 31.

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