Do sulfate reducing bacteria ingest their sulfate as solid, or liquid or gas?

I understand that almost all forms of sulfate are solid.. and sulfate can be dissolved in water(thus no longer solid, but liquid).

So, do sulfate reducing bacteria ingest sulfate in its solid form, or do they require it to be dissolved in water?

A similar question in fact, for nitrifying bacteria, though if that's complex I might make it a separate question.

Also, even though it's respiration(which tends to be associated either with the breathing process - in the case of physiological respiration, or with having breathed prior - in the case of cellular respiration), here it's not using a gas. So i'm curious if biologists ever use the word "breathing" for such a process. wikipedia for example, says https://en.wikipedia.org/wiki/Sulfate-reducing_bacteria " In a sense, these organisms "breathe" sulfate.." I wonder if biologists use the term 'breath' in such a general sense(to include consuming a substance dissolved in water), or only in a specific sense of gas or air, or if they don't use the term 'breath' at all. So, how strictly is the term breath defined in biology.


1 Answer 1


Sulfates in water would not be liquid. Their melting points are far to high. When a sulfate dissolves into sulfate ions and some cation such as potassium, we say it is solvated, not liquid. Sulfates would also not be present as gasses due to their ionic nature as well as high molecular weights. So that leaves solvated sulfate ions and solid sulfates that have not completely dissolved.

To be ingested in bulk as a solid would require endocytosis which is not performed by prokaryotes: http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit1/proeu/proeu.html

Further research indicates sulfate, as ions, enters the cell through permeases: http://citeseerx.ist.psu.edu/viewdoc/download?doi=

Edit: Here's some files to help with the idea of how ions and other molecules enter cells. Again, bacteria do not engulf substances whole, in the process of endocytosis, such as eukaryotes are capable of. Here is an image of a nitrate ion within a transport protein. Only a few amino acids of the protein are shown here, the actual protein is much larger and spans across the entire membrane creating a channel for the ion to enter. http://www.rcsb.org/pdb/ngl/ngl.do?pdbid=4U4W&preset=ligandInteraction&sele=[NO3]

Here's another channel, aquaporin, which allows transport of water across the membrane. http://pdb101.rcsb.org/motm/173 The top left image shows the channel in the protein leading to the interior. The third image down shows the interaction between the water and the amino acids (backbones only are shown) which facilitate the water's passage.

  • $\begingroup$ what about salt.. when it breaks into Na and Cl, ions, are they also still solid? also I heard that most sulfate is solid but "dihydrogen sulfate" is a liquid, is that wrong? $\endgroup$
    – barlop
    Feb 5, 2017 at 18:05
  • $\begingroup$ @barlop. No. Solids are formed when the particles have close neighbors that have fixed positions relative to one another. When in water, most ionic substances, such as table salt, have their ions pulled apart from one another by attractions to the water molecules. Sulfate ions, being negative, will be surrounded by the partial positive charges on surrounding water molecules. This allows them to be delivered one at a time to the proteins, permeases in the case, that transport them into the cell $\endgroup$
    – bpedit
    Feb 5, 2017 at 18:28
  • $\begingroup$ is it the same situation with nitrifying bacteria - the bacteria can consume small amounts of solid nitrate, and larger amounts of solvated nitrate? Also in the case of a tiny bit of solid nitrate(not dissolved), does it need to be in water for the bacteria to accept it, or can it accept it dry? $\endgroup$
    – barlop
    Feb 5, 2017 at 20:18
  • $\begingroup$ @barlop. I suspect the presence of a certain amount of water is essential. Even if most of the neighboring nitrate is in solid form, the nitrate ions would have to be peeled away as solvated ions before interacting with the prpteins that transport them into the bacteria. ncbi.nlm.nih.gov/pubmed/11289303 $\endgroup$
    – bpedit
    Feb 5, 2017 at 21:18
  • $\begingroup$ can you comment on the use of the term breathing (see last paragraph of my question) $\endgroup$
    – barlop
    Feb 6, 2017 at 4:01

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