Chapter 29, Problem 1CHI

How might you attempt to grow in the laboratory a chemolithoautotroph that uses ferrous iron as an electron donor and oxygen as an electron acceptor?

Summary Introduction

The culture media may be complex, defined, supportive, enriched, selective, and differential. The culture media possess the same qualities that are needed by the microbes as if they grow in their natural habitat. The culture media can be modified according to the nutritional needs of the microbes.

Explanation of Solution

Some of the organism can effectively trap the energy in the form of inorganic chemicals are known as chemolithoautotrophs. Most of the inorganic compounds are iron, ammonia, and hydrogen sulfide. The chemolithoautotrophs effectively converse energy, uses the inorganic compounds that are released as waste by the chemoorganoheterotrophs oxidize to release ATP.

To grow a chemolithoautotroph in the lab with oxygen as the electron acceptor and ferrous iron as the electron donor one should incubate the organism in the presence of carbonate, oxygen, FeSO₄ at acidic pH. The absence of oxygenic conditions selects against anaerobes and absence of organic carbon selects against the heterotrophs. The growth of phototrophs is simply prevented by incubating cultures in the dark. Candidate strains isolation is prevented by performing plating directly an environmental sample into the designed solid medium or by plating and isolation of the colony.