Trace elements required by microorganisms include which of the following?

Trace elements are essential minerals that microorganisms require in very small quantities for various biochemical processes. The correct answer indicates manganese, zinc, and cobalt as trace elements necessary for microbial growth and function.

Manganese acts as a cofactor for several enzymes, playing a crucial role in the antioxidant defense mechanism and in metabolic pathways. Zinc is vital for the structural integrity of proteins and is a cofactor in numerous enzymatic reactions, influencing protein synthesis, nucleic acid metabolism, and cell signaling. Cobalt is necessary for the production of vitamin B12, which is essential for DNA synthesis and cellular metabolism in many microorganisms.

The other choices include elements that either do not qualify as trace elements or are not specifically required in trace amounts by microorganisms. Sodium, potassium, and calcium, for example, are typically considered macronutrients as they are needed in larger amounts for various cellular functions, such as maintaining osmotic balance and enzyme activity. Iodine and phosphorus are also essential but do not fit the definition of trace elements and are more abundant in biological systems compared to the elements listed in the correct option.