> Cell sizes are not fixed, however, even within a single species. Cells often swell as they increase their production of proteins and metabolites in preparation for division. This is in line with biology’s only rule: namely, there are exceptions to every rule!
> Case in point: a giant bacterium called Thiomargarita magnifica can extend about one centimeter in length, so large that it can be seen by the naked eye. It does so by breaking the surface area-to-volume rule, filling between 65–80 percent of its internal volume with an empty vacuole. In other words, it pushes most of its molecules to the cell periphery, thus shortening diffusion distances.
There is also a captioned image of bubble algae in the post.
Collected and stored sediment samples were found to have surviving T. namibiensis cells after over two years. The cells had no access to any added sulfide or nitrate during this time. In the surviving cells, there was a notable size decrease. To survive without growing the cells depended on the nutrient stores of the central vacuoles.
Indeed. It says they rely on two different substances which normally don't mix (nitrates and sulfites), presumably because if they were both present at the same time they'd react with each other directly without the bacterium extracting any energy from that. So they live in places that sometimes have one and sometimes the other, and have to store one of them until the other comes along, which can be years. Or that's how I read it.
Agreed. Humans draw rather arbitrary distinctions. It was quite funny in regards to viruses, aka parasite. Mimivirus are still a parasite, of course, but they even encode genes for metabolic pathways and are larger than some bacteria.
See:
"The Mimivirus is a giant virus that infects amoebae and was long considered to be a bacterium due to its size."
Although for me, I always used the definitions through the genetic information available (genome). So as long as a virus still is a parasite, I'd hold up that definition. It will be interesting when viruses are found that are even closer to a cell, e. g. some life cycle where they could switch between parasitism and stand-alone metabolism (or some hybrid in between; I mean if they can encode whole metabolic pathways, at the least some or some parts of it, the threshold here should not be impossible to overcome, and then the whole definition of a virus also has to be adapted since it would no longer make sense).
Granted, they are grouped both in Thiomargarita. 2cm is pretty gigantic. What I always found more interesting was that they don't merely have just one genome.
These both feature large central vacuoles, lending support the thesis of the article that the cubic growth in volume outstrips the quadratic increase in surface area for transferring nutrients and waste across the cell membrane.
Those still seem kind of small? Why not the size of an mature olive tree for example? I'm guessing the article may answer this, haven't gotten that far yet.
> Case in point: a giant bacterium called Thiomargarita magnifica can extend about one centimeter in length, so large that it can be seen by the naked eye. It does so by breaking the surface area-to-volume rule, filling between 65–80 percent of its internal volume with an empty vacuole. In other words, it pushes most of its molecules to the cell periphery, thus shortening diffusion distances.
There is also a captioned image of bubble algae in the post.