Question

Which of the following is not a common nitrogen source used in cultivation media for microorganisms?

• A. Ammonium sulfate
• B. Peptone
• C. Urea
• D. Glucose

Hint:

• Nitrogen sources provide the element nitrogen (N) for microbial growth.
• Common inorganic nitrogen sources: ammonium salts (e.g., ammonium sulfate), nitrate salts.
• Common organic nitrogen sources: amino acids, peptides, proteins (e.g., peptone, yeast extract, beef extract), urea.
• Glucose (C$_6$H$_{12$O$_6$)} is a carbohydrate; it is a primary source of carbon and energy, not nitrogen.

Answer 1

The Correct Option is D

Microorganisms require various nutrients for growth, including a source of nitrogen for the synthesis of proteins, nucleic acids, and other nitrogen-containing cellular components. Cultivation media must provide these nutrients in usable forms. Common nitrogen sources include:

• Ammonium sulfate ((NH$_4$)$_2$SO$_4$) (option a): Ammonium salts are readily utilized inorganic nitrogen sources for many microorganisms. The ammonium ion (NH$_4^+$) can be directly incorporated into amino acids.
• Peptone (option b): Peptones are protein hydrolysates, typically produced by enzymatic digestion or acid hydrolysis of proteins (e.g., from meat, casein, soy). They provide a rich source of amino acids, short peptides, and other nitrogenous compounds, as well as carbon and growth factors. They are a common component of complex media.
• Urea (CO(NH$_2$)$_2$) (option c): Urea can be used as a nitrogen source by microorganisms that possess the enzyme urease. Urease hydrolyzes urea into ammonia (NH$_3$) and carbon dioxide (CO$_2$). The ammonia can then be assimilated.
• Glucose (C$_6$H$_{12}$O$_6$) (option d): Glucose is a simple sugar (a carbohydrate). Its chemical formula shows it contains carbon, hydrogen, and oxygen, but no nitrogen. Glucose is primarily used as a carbon source (for building cellular components) and an energy source by many microorganisms. It does not serve as a nitrogen source.

Therefore, glucose is not a common nitrogen source. \[ \boxed{\text{Glucose}} \]