Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: Lewis Thomson on 12/05/2022 14:26:38
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Donald has emailed in to ask this question to the forum,
"Humans and most living organisms have a finite lifespan. How about asexual unicellular bacteria? Do they eventually die if they don't reproduce? Do they have a lifespan? If so, why would the lifespan reset with reproduction? Do HeLa cells have a lifespan? Can they persist without reproducing? Or the contagious cancers in Tasmanian devil's? Life! What can it not do?"
Discuss your answers in the comments below...
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Unicellular bacteria are effectively immortal. Provided they have food and a suitable environment, they can continue to divide forever (provided they don't get too overcrowded).
- When they get overcrowded, evolution takes over; some strains survive better in crowded conditions, and outcompete those that are less fit for these resource-limited conditions.
In one sense, cancer cells have almost reverted to a unicellular state, where it is "every cell for itself", to the detriment of the body in which they originated. Most cancers are limited to one individual - any cancer cells that transfer to another individual are recognized as "alien" and destroyed by the recipient's immune system.
- However, in inbred populations, transmissible tumors can be transferred from one individual to another, without being destroyed by the other individual's immune system.
- Examples of this are the Tasmanian Devil facial tumor, Canine sexually-transmitted cancer, and a cancer of shellfish.
https://en.wikipedia.org/wiki/Clonally_transmissible_cancer
Can they persist without reproducing?
Some unicellular organisms discovered deep in a gold mine have a very low metabolic rate, and it is thought that individual may go many decades between divisions.
Unicellular organisms engage in "Horizontal gene transfer", which is a way to share useful snippets of DNA, which introduces more genetic variability than the usual cellular division. This helps them cope with extreme conditions.
See: https://en.wikipedia.org/wiki/Extremophile