The Duhem Model and Hysteresis: A Symbiotic Relationship?

Author(s):  
Fayçal Ikhouane
Author(s):  
K.W. Lee ◽  
R.H. Meints ◽  
D. Kuczmarski ◽  
J.L. Van Etten

The physiological, biochemical, and ultrastructural aspects of the symbiotic relationship between the Chlorella-like algae and the hydra have been intensively investigated. Reciprocal cross-transfer of the Chlorellalike algae between different strains of green hydra provide a system for the study of cell recognition. However, our attempts to culture the algae free of the host hydra of the Florida strain, Hydra viridis, have been consistently unsuccessful. We were, therefore, prompted to examine the isolated algae at the ultrastructural level on a time course.


Author(s):  
R. N. Tomas

Peridinium balticum appears to be unusual among the dinoflagellates in that it possesses two DNA-containing structures as determined by histochemical techniques. Ultrastructurally, the two dissimilar nuclei are contained within different protoplasts; one of the nuclei is characteristically dinophycean in nature, while the other is characteristically eucaryotic. The chloroplasts observed within P. balticum are intrinsic to an eucaryotic photosynthetic endosymbiont and not to the dinoflagellate. These organelles are surrounded by outpocketings of endoplasmic reticulum which are continuous with the eucaryotic nuclear envelope and are characterized by thylakoids composed of three apposed lamellae. Girdle lamellae and membranebounded interlamellar pyrenoids are also present. Only the plasmalemma of the endosymbiont segregates its protoplast from that of the dinophycean cytoplasm. The exact nature of this symbiotic relationship is at present not known.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Krista L. Plett ◽  
Sean L. Bithell ◽  
Adrian Dando ◽  
Jonathan M. Plett

Abstract Background The ability of chickpea to obtain sufficient nitrogen via its symbiotic relationship with Mesorhizobium ciceri is of critical importance in supporting growth and grain production. A number of factors can affect this symbiotic relationship including abiotic conditions, plant genotype, and disruptions to host signalling/perception networks. In order to support improved nodule formation in chickpea, we investigated how plant genotype and soil nutrient availability affect chickpea nodule formation and nitrogen fixation. Further, using transcriptomic profiling, we sought to identify gene expression patterns that characterize highly nodulated genotypes. Results A study involving six chickpea varieties demonstrated large genotype by soil nitrogen interaction effects on nodulation and further identified agronomic traits of genotypes (such as shoot weight) associated with high nodulation. We broadened our scope to consider 29 varieties and breeding lines to examine the relationship between soilborne disease resistance and the number of nodules developed and real-time nitrogen fixation. Results of this larger study supported the earlier genotype specific findings, however, disease resistance did not explain differences in nodulation across genotypes. Transcriptional profiling of six chickpea genotypes indicates that genes associated with signalling, N transport and cellular localization, as opposed to genes associated with the classical nodulation pathway, are more likely to predict whether a given genotype will exhibit high levels of nodule formation. Conclusions This research identified a number of key abiotic and genetic factors affecting chickpea nodule development and nitrogen fixation. These findings indicate that an improved understanding of genotype-specific factors affecting chickpea nodule induction and function are key research areas necessary to improving the benefits of rhizobial symbiosis in chickpea.


Author(s):  
Daniel Sodano ◽  
Joseph DeCarolis ◽  
Anderson Rodrigo de Queiroz ◽  
Jeremiah X. Johnson

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Osamu Kagawa ◽  
◽  
Shota Uchida ◽  
Daishi Yamazaki ◽  
Yumiko Osawa ◽  
...  

AbstractEnvironmental factors promote symbiosis, but its mechanism is not yet well understood. The alga Pseudocladophora conchopheria grows only on the shell of an intertidal gastropod Lunella correensis, and these species have a close symbiotic relationship which the alga reduces heat stress of the gastropod. In collaboration with general public, we investigated how environmental conditions alter the symbiotic interaction between the alga and the gastropod. Information about the habitats of each gastropod and images of shells was obtained from the Japanese and Korean coasts via social media. We constructed the hierarchical Bayesian model using the data. The results indicated that the proportion of shell area covered by P. conchopheria increased as the substrate size utilized by the gastropod increased. Meanwhile, temperature did not affect the proportion of P. conchopheria on the shell. These suggested that the alga provides no benefits for the gastropod on small substrates because gastropod can reduce the heat stress by diving into the small sediment. Further, the gastropod’s cost incurred by growing the alga on the shell seems to be low as the algae can grow even in cooler places where no benefits of heat resistance for gastropods. Different environments can yield variable conditions in symbiosis.


2011 ◽  
Vol 28 (2) ◽  
pp. 151-169 ◽  
Author(s):  
Michael A. Rynkiewich

Abstract There was a time when mission studies benefitted from a symbiotic relationship with the social sciences. However, it appears that relationship has stagnated and now is waning. The argument is made here, in the case of cultural anthropology both in Europe and the United States, that a once mutually beneficial though sometimes strained relationship has suffered a parting of the ways in recent decades. First, the article reviews the relationships between missionaries and anthropologists before World War II when it was possible to be a ‘missionary anthropologist’ with a foot in both disciplines. In that period, the conversation went two ways with missionary anthropologists making important contributions to anthropology. Then, the article reviews some aspects of the development of the two disciplines after World War II when increasing professionalism in both disciplines and a postmodern turn in anthropology took the disciplines in different directions. Finally, the article asks whether or not the conversation, and thus the cross-fertilization, can be restarted, especially since the youngest generation of anthropologists has recognized the reality of local Christianities in their fields of study.


Author(s):  
Paula Corabian ◽  
Bing Guo ◽  
Carmen Moga ◽  
N. Ann Scott

AbstractObjectivesThis article retrospectively examines the evolution of rapid assessments (RAs) produced by the Health Technology Assessment (HTA) Program at the Institute of Health Economics over its 25-year relationship with a single requester, the Alberta Health Ministry (AHM).MethodsThe number, types, and methodological attributes of RAs produced over the past 25 years were reviewed. The reasons for developmental changes in RA processes and products over time were charted to document the push–pull tension between AHM needs and the HTA Program's drive to meet those needs while responding to changing methodological benchmarks.ResultsThe review demonstrated the dynamic relationship required for HTA researchers to meet requester needs while adhering to good HTA practice. The longstanding symbiotic relationship between the HTA Program and the AHM initially led to increased diversity in RA types, followed by controlled extinction of the less fit (useful) “transition species.” Adaptations in RA methodology were mainly driven by changes in best practice standards, requester needs, the healthcare environment, and staff expertise and technology.ConclusionsRAs are a useful component of HTA programs. To remain relevant and useful, RAs need to evolve according to need within the constraints of HTA best practice.


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