Question

Although many cloning applications involve introducing recombinant DNA into bacterial host cells, many other cell types are also used as hosts for recombinant DNA. Why?

Short answer

Answer: Other cell types, such as yeast, insect, and mammalian cells, are used as hosts for recombinant DNA because they offer unique advantages for producing specific proteins. Bacterial host cells may not be able to synthesize some proteins, or the resulting protein structure may not be appropriate for the desired application. Some proteins require specific modifications (such as glycosylation) that cannot be achieved in bacterial cells. The choice of host cell depends on the desired properties and applications of the protein being produced.

Step-by-step solution

Introduction to recombinant DNA and bacterial host cells

Recombinant DNA technology involves the introduction of foreign DNA into a host cell to produce specific proteins by cloning genes. It commonly uses bacterial host cells, such as Escherichia coli (E. coli), as hosts due to their ability to replicate quickly, their well-understood genetic system, and ease of genetic manipulation.

Importance of using multiple host cells

While bacterial host cells are frequently used, it is important to use different host cells depending on the specific needs and desired outcomes of the experiment. Some proteins cannot be synthesized in bacteria, or the resulting protein structure may not be appropriate for the desired application. Additionally, some proteins require specific modifications (such as glycosylation) that cannot be achieved in bacterial cells, necessitating the use of other host cell types.

Examples of alternate host cells

There are various other host cell types which can be used for recombinant DNA, including yeast cells, insect cells, and mammalian cells, each of which can offer specific advantages.

Yeast cells

Yeast cells, such as Saccharomyces cerevisiae, are eukaryotic organisms and are capable of carrying out post-translational modifications (such as glycosylation) that bacteria cannot perform. They are also well-suited for high-level expression of heterologous genes and are easier to grow and manipulate than some other eukaryotic cells.

Insect cells

Insect cells, like those from the Spodoptera frugiperda (Sf9) line, are used with the baculovirus expression system (a viral vector) for high-level protein production. The insect cell-baculovirus system is capable of producing large and complex proteins that require specific folding and post-translational modifications.

Mammalian cells

Mammalian cells, such as Chinese hamster ovary (CHO) and human embryonic kidney (HEK) cells, can accurately synthesize, correctly fold, and modify proteins that require complex features found exclusively in higher eukaryotic cells. These capabilities make mammalian cells invaluable for producing proteins for use in therapeutic applications where the structural integrity of the protein is crucial to its function. In conclusion, although bacterial host cells are commonly used for recombinant DNA technology, other host cells like yeast, insect, and mammalian cells offer unique advantages for producing specific proteins. The choice of host cell depends on the desired properties and applications of the protein being produced.