The size of the bacteria can be different in eight orders of magnitude - if the smallest bacteria is as large as human hands, then its giant "relative" can hold 4000 tractor trailer. However, despite that the growth and reproduction of large bacterial is faster, there is a limit in how big these microorganisms can grow.
To clarify the reason, computational biologists proposed a computer model to predict how bacteria metabolism and cellular components change with the different size of cells. They used the principle of how much a bacteria need make it "assembly" --the normal operating details of DNA, protein and molecule factory which is called ribosome.
The researchers recently published a study in the Journal of the International Society for Microbial Ecology, reporting that space limitation simultaneously controls the maximum and minimum size of bacteria. Bacteria won't be smaller than their same kinds whose size has reduced. Because if so, there is not enough space for essential DNA and proteins. And they can't change much larger, because the larger species need a lot more energy requirements with its increased size. Therefore, they need more ribosomes, while bacteria which try to keep those records larger than the existing bacteria can't hold additional ribosomes it needs.
The researchers said that the understanding of the minimum size of bacteria can help life biologists who are looking for extraterrestrial life exclude too tiny life signs. At the same time, with understanding of the maximum size of bacteria, biologists can more conduct careful study on how other microorganisms like unicellular eukaryotes deal with this limit.
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