Signaling and Behavior in Protists
COVER: Avelina Espinosa & Guillermo Paz-y-Miño-C. 2019. Discrimination Experiments in Entamoeba and Evidence from other Protists Suggest Pathogenic Amebas Cooperate with Kin to Colonize Hosts and Deter Rivals. Journal of Eukaryotic Microbiology 66: 354–368. Entamoeba histolytica is one of the least understood protists in terms of taxa, clone, and kin discrimination/recognition ability. However, the capacity to tell apart same or self (clone/kin) from different or nonself (nonclone/nonkin) has long been demonstrated in pathogenic eukaryotes like Trypanosoma, Plasmodium, free‐living social amebas (Dictyostelium, Polysphondylium), budding yeast (Saccharomyces), and in numerous bacteria and archaea (prokaryotes). Kin discrimination / recognition is explained under inclusive fitness theory; that is, the reproductive advantage that genetically closely related organisms (kin) can gain by cooperating preferably with one another (rather than with distantly related or unrelated individuals), minimizing antagonism and competition with kin, and excluding genetic strangers (or cheaters = noncooperators that benefit from others’ investments in altruistic cooperation). In this review, we rely on the outcomes of in vitro pairwise discrimination/recognition encounters between seven Entamoeba lineages to discuss the biological significance of taxa, clone, and kin discrimination/recognition in a range of generalist and specialist species (close or distantly related phylogenetically). We then focus our discussion on the importance of these laboratory observations for E. histolytica 's life cycle, host infestation, and implications of these features of the amebas’ natural history for human health (including mitigation of amebiasis). PDF in Publications.
Anaerobic Eukaryotes: Cell Biology, Biochemistry
Kin discrimination contributes to the evolution of cooperation in animals, but is less known in unicellular microbes. We use the human parasite Entamoeba histolytica and its relatives, which live in a range of hosts (including reptiles, birds and mammals), and freely in ponds and still waters. E. invadens-VK-1NS and E. invadens IP-1 infect reptiles. E. invadens-VK-1NS was isolated from lizards and IP-1 was isolated from snakes. Our research on the Entamoeba lineage suggests that these protists discriminate and associate with members of their own kin, a feature previously attributed only to social microbes. For the theory and empirical testing on this project check our publications: Espinosa & Paz-y-Miño-C, 2012, 2014a, 2014b; Paz-y-Miño-C & Espinosa 2016; Espinosa et al. 2016, 2019.
Metabolic proteins are essential for survival. The human parasite Entamoeba histolytica lives in the anaerobic environment of the gut. It relies on a bifunctional enzyme to obtain energy: EhADH2. We design and test inhibitors that block the enzymes’ activities and inhibit parasite growth for treatment purposes. The last stages of the glycolytic pathway convert acetyl-CoA into ethanol by the enzymatic activities of aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH). These functions are fused in E. histolytica alcohol dehydrogenase 2 (EhADH2), which is essential for the survival of E. histolytica. AdhE, a homologous Escherichia coli enzyme, is required for bacterial fermentative growth. Episomal expression of ehadh2 gene in E. coli complements an adhE knock-out mutation, providing a system for inhibitor identification. Site-directed mutagenesis of conserved histidines at the iron-binding domain of EhADH2 inactivates ADH and ALDH, thus rendering the mutant proteins unable to rescue anaerobic growth of E. coli SHH31(ΔadhE). Although our previous analyses suggest that iron is important for amoebic growth and enzymatic activities, the physiological role of iron in amoebic growth or EhADH2 function had not been elucidated. Studies have emphasized the importance of iron in pathogenic diseases and suggested iron chelation as chemotherapy, based on mammalian immune responses that sequester iron as the first line of defense. Iron affects ADH and ALDH enzymatic activities and trophozoite survival. We propose that iron starvation could be further explored as treatment for amoebiasis. For the theory and empirical testing on this project check our publications: Espinosa et al. 2001, 2004, 2009, 2012.
Natural Products for Managing Amebiasis
Espinosa et al. 2020: Anti-amebic effects of Chinese rhubarb (Rheum palmatum) leaves' extract, the anthraquinone rhein and related compounds. Here we provide experimental evidence that Chinese rhubarb (Rheum palmatum) leaves' extract (rich in the anthraquinone rhein) inhibits E. histolytica trophozoite growth in vitro. In addition, from a set of ten isolated/synthetic anthraquinones (which we suspected to have anti-amebic properties), four analogs (rhein; AHHDAC = 1-amino-4-hydroxy-9, 10-dioxo-9, 10-dihydro-anthracene-2-carboxylic acid; unisol blue AS; and sennoside B) efficiently inhibited amebic growth at EIC50 concentrations comparable to metronidazole. The mechanism of action of these compounds still needs to be determined, although anthraquinones might enhance the production of toxic oxygen metabolites as it has been suggested for various protists (e.g. Leishmania, Plasmodium, Trypanosoma). Our research is the first to explore anti-amebic effects of Chinese rhubarb leaves' extract and isolated/synthetic anthraquinones on pathogenic Entamoeba. PDF in Publications.
Evolution Controversy: a Phenomenon Prompted by the Incompatibility between Science and Religious Beliefs
Paz-y-Miño-C, G. & Espinosa, A. 2015. Evolution Controversy: A Phenomenon Prompted by the Incompatibility between Science and Religious Beliefs.
The incompatibility between science and the belief in supernatural causation helps us understand why people do not accept evolution. Belief disrupts, distorts, delays, or stops (3Ds + S) the acceptance of scientific evidence. Here we examine the evolution controversy under three predictions of the incompatibility hypothesis. First, chronological-conflict-and-accommodation, which explains the historical re-emergence of antagonism between evolution and religion when advances in science continue to threaten the belief in supernatural causation; in such situations, creationists’ rejection of and subsequent partial acceptance of the new scientific discoveries are expected. Second, change in evolution's acceptance as function of educational attainment, which explains the positive association between acceptance of evolution and level of education. And third, change in evolution's acceptance as function of religiosity, which explains the negative association between acceptance of evolution and level of religious beliefs. We rely on an ample assessment of the attitudes toward evolution by highly-educated audiences (i.e. research faculty, educators of prospective teachers, and college students in the United States) to characterize the associations among the understanding of science and evolution, personal religious convictions, and conservative ideology. We emphasize that harmonious coexistence between science and religion is illusory. If co-persisting in society, their relationship will fluctuate from moderate to intense antagonism. PDF in Publications.
The incompatibility between science and the belief in supernatural causation helps us understand why people do not accept evolution. Belief disrupts, distorts, delays, or stops (3Ds + S) the acceptance of scientific evidence. Here we examine the evolution controversy under three predictions of the incompatibility hypothesis. First, chronological-conflict-and-accommodation, which explains the historical re-emergence of antagonism between evolution and religion when advances in science continue to threaten the belief in supernatural causation; in such situations, creationists’ rejection of and subsequent partial acceptance of the new scientific discoveries are expected. Second, change in evolution's acceptance as function of educational attainment, which explains the positive association between acceptance of evolution and level of education. And third, change in evolution's acceptance as function of religiosity, which explains the negative association between acceptance of evolution and level of religious beliefs. We rely on an ample assessment of the attitudes toward evolution by highly-educated audiences (i.e. research faculty, educators of prospective teachers, and college students in the United States) to characterize the associations among the understanding of science and evolution, personal religious convictions, and conservative ideology. We emphasize that harmonious coexistence between science and religion is illusory. If co-persisting in society, their relationship will fluctuate from moderate to intense antagonism. PDF in Publications.