Immortal jellyfish (Turritopsis dohrnii) has the ability to rejuvenate during its post-reproductive stage as a medusa.
Medusa is the free-swimming form of a jellyfish at which the shape is like an umbrella with tentacles around the edges.
The biological immortality of this jellyfish challenges our knowledge of aging.
Researchers compared genomes of T. dohrnii (immortal) and T. rubra (mortal).
Researchers identified genes associated with DNA repair, telomere, replication, redox environment, stem cell abundance, and communication between cells.
Researchers found that the polycomb repressive complex 2 targets were silenced.
Polycomb repressive complex 2 plays an important function during development, and it is responsible for maintaining the repressive states of many developmental genes.
Additionally, researchers found that pluripotency targets were activated.
Pluripotency is ability of a cell to develop into the three primary germ cell layers namely ectoderm, mesoderm and endoderm.
The research highlights these factors as important elements in the ability of immortal jellyfish to undergo rejuvenation.
Pascual-Torner, M., Carrero, D., Pérez-Silva, J. G., Álvarez-Puente, D., Roiz-Valle, D., Bretones, G., Rodríguez, D., Maeso, D., Mateo-González, E., Español, Y., Mariño, G., Acuña, J. L., Quesada, V., & López-Otín, C. (2022). Comparative genomics of mortal and immortal cnidarians unveils novel keys behind rejuvenation. Proceedings of the National Academy of Sciences of the United States of America, 119(36), e2118763119. https://doi.org/10.1073/pnas.2118763119
Frogs can grow more legs if infected with a parasite
Do you know that a frog can have more legs if infected with a parasite?
Parasites can change the structure of their host.
For example, some trematodes can cause limb malformations in amphibians.
Researchers examined the relationship between morphological abnormalities in amphibians and the abundance of trematode parasites infection.
The research covered parts of California, Idaho, Washington, Oregon, and Montana.
Researchers studied malformations at frequencies ranging between 1 to 90 percent in nine amphibian species.
Researchers discovered that Ribeiroia ondatrae was linked to higher occurrence of amphibian limb malformations.
The parasite can be found mostly around the basal tissue of the hind limbs in infected frogs.
The malformations included skin webbings, more limbs and digits, and missing/malformed hind limbs.
Amphibians without the parasite showed significantly less occurrence of abnormalities.
The species that exhibited the highest abnormality frequencies include Ambystoma macrodactylum, Hyla regilla, Rana aurora, R. luteiventris, and Taricha torosa.
Water quality did not show significant relationship with the malformations.
The snail Planorbella were significant predictors of the presence of Ribeiroia infection.
The discovery demonstrated that Ribeiroia infection is the cause of amphibian malformations of the limbs in the western United States.
Johnson, Pieter & Lunde, Kevin & Thurman, Earl & Ritchie, Euan & Wray, Simon & Sutherland, Daniel & Kapfer, Joshua & Frest, Terrence & Bowerman, Jay & Blaustein, Andrew. (2002). Parasite (Ribeiroia ondatrae) Infection Linked to Amphibian Malformations in the Western United States. Ecological Monographs. 72. 151-168. 10.2307/3100022.
Remaining non-resistant pathogens after an antibiotic treatment may help control the growth of the resistant type
Infectious disease practice calls for an effective drug treatment that quickly eliminates the pathogen before the resistant-type can emerge.
When the resistant pathogen is not present, this quick elimination strategy can lead to cure.
However, when the resistant pathogen is present, quick elimination of the non-resistant ones removes the barriers that controls the growth of the resistant pathogen.
Researchers developed a strategy which maintain a maximum tolerable population of the non-resistant pathogens, utilizing competitive suppression to gain long-term control.
Researchers measured the time required for resistant Escherichia coli populations to escape the threshold density produced by the effect of antibiotic.
Resistant E. coli without the non-resistant populations quickly escape the threshold density.
However, resistant E. coli that also has the maximum possible number of non-resistant cells could be controlled for a lot longer.
The increase in escape time happens only when the acceptable bacterial burden is significantly high.
This discovery confirms that maintaining the maximum number of non-resistant cells can help control the resistant type when the population size is sufficiently large.
Hansen E, Karslake J, Woods RJ, Read AF, Wood KB (2020) Antibiotics can be used to contain drug-resistant bacteria by maintaining sufficiently large sensitive populations. PLoS Biol 18(5): e3000713. https://doi.org/10.1371/journal.pbio.3000713