Which of the following is true of bacterial strains?

A. They are closely related subtypes within a bacterial species that may or may not have similar properties.

B. They are informal bacterial groupings used for medical distinctions but not recognized for classification purposes.

C. They are more distantly related to each other than are members of a single bacterial species.

D. They are very similar bacteria with almost identical properties.

Bacterial strains are closely related subtypes within a bacterial species that can have differing properties and behaviors. Some strains may be harmless while others can cause disease, as seen in different strains of Escherichia coli. This understanding highlights the significance of bacterial classification in biology.

Explanation:

Bacterial Strains

In biology, a bacterial strain refers to a subgroup of a bacterial species. Strains are closely related and share a significant amount of genetic material, but they can exhibit different properties and behaviors.

There are several characteristics that define bacterial strains:

Strains may possess subtle genetic differences that result in varying biochemical activities.
Some strains can be harmless, while others might be pathogenic, even within the same species.
For example, the bacterium Escherichia coli has strains that are part of the normal gut flora, but other strains can cause severe food poisoning.

While strains are informally used for medical distinctions, they can show significant differences in virulence and biochemical properties despite being categorized under the same species.

Therefore, the correct statement from the options provided is: They are closely related subtypes within a bacterial species that may or may not have similar properties.

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