Consider the following statements: [Basic Biology]

I. No virus can survive in ocean waters.

II. No virus can infect bacteria.

III. No virus can change the cellular transcriptional

activity in host cells.

How many of the statements given above are correct?

The correct option is None.

To understand why none of the three statements are correct, let us analyze each statement step-by-step:

Statement I: "No virus can survive in ocean waters."
This statement is incorrect. Ocean waters are teeming with viral life. In fact, marine viruses are extremely abundant and play a critical role in global biogeochemical cycles, particularly the carbon cycle, by lysing bacterial and algal cells (a process known as the "viral shunt"). Therefore, viruses not only survive but thrive in marine environments.

Statement II: "No virus can infect bacteria."
This statement is incorrect. Viruses that specifically infect, replicate within, and destroy bacteria are well-known and are called bacteriophages (or simply phages). Phages are among the most common and diverse entities in the biosphere.

Statement III: "No virus can change the cellular transcriptional activity in host cells."
This statement is incorrect. Upon infecting a host cell, a primary strategy of many viruses is to hijack the host's cellular machinery. Viruses routinely alter the transcriptional activity of host cells to prioritize the transcription and translation of viral genes over the host's own cellular genes. Some viruses encode transcription factors or modify host RNA polymerases to achieve this reprogramming.

Since Statement I, Statement II, and Statement III are all false, the number of correct statements is zero.