MadSci Network: Microbiology

Re: What are chemolithrotrophic bacteria?

Date: Fri Nov 9 14:34:58 2001
Posted By: Andrew D. Brabban, Faculty, Biology, The Evergreen State College
Area of science: Microbiology
ID: 1002505873.Mi

Chemolithotrophy is a biological process that we as humans often overlook, 
but whose impact on our lives and the environment should not be overlooked. 
These organisms are key in everyday processes such as nutrient cycling, and 
problems such as acid mine drainage.

A good place to start here is the word. What does it mean? A good way to 
analyse science words is to break them down into their parts.
CHEMO = chemical
LITHO = rock
TROPH = to eat.
From this simple process we get the idea that chemolithotrophs are rock 
eaters. Not a perfect definition, but a good basic view of them. To be more 
precise they use inorganic compounds as energy sources (electron donors) 
for their catabolism (the biological process of making energy). You, as a 
human are a organotroph and use organic chemicals (sugars, fats, and 
proteins) such as glucose as an energy source. This process of using 
inorganic compounds generates less energy per molecule consumed.

You also mention the idea of autotrophy. Again lets look at the words.
AUTO = self
TROPH = to eat.
We use this term to mean organisms that can use carbon from non-organic 
forms for anabolism. Anabolism is the process of building new cellular 
material. Plants for example are autotrophs that can turn carbon dioxide 
into glucose. You, a human can not.

Finally, how are these 2 interrelated and what types of organisms are they? 
If you live and have evolved to grown in an environment depleted of carbon 
for energy (catabolism) there would also be no carbon for new cell 
(anabolism). Therefore most of the organisms that are chemolithotrophs are 
also autotrophs, but not all. All of the organisms that do these reactions 
are single celled and most prokaryotes (bacteria and archaea). A good 
example for you to research would be Thiobacillus ferreoxidans. This causes 
acid mine drainage in many states and uses sulphur (thio) and iron (ferre) 
in its metabolism.

I hope this helps you. Chemolithotrophs are extremely fun organisms that we 
still need to do a great deal of work on.

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