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In the Pacific Ocean, air and ocean temperatures, atmospheric carbon dioxide, landings of anchovies and sardines, and the productivity of coastal and open ocean ecosystems have varied over periods of about 50 years. In the mid-1970s, the Pacific changed from a cool “anchovy regime” to a warm “sardine regime.” A shift back to an anchovy regime occurred in the middle to late 1990s. These large-scale, naturally occurring variations must be taken into account when considering human-induced climate change and the management of ocean living resources.

This brief survey of bacteriophage infection has provided support for an obvious but important generalization: that the study of virus infection at the cellular level is a branch of cellular genetics. The interactions between viral and cellular functions show that infection with a virus is not just a disrupting intrusion; it is an addition to the cellular endowment of genetic specificity. The outcome of this addition depends on the nature of the instructions carried by the viral genome, on the ability of the cellular machinery to carry out these instructions, and on the availability of control mechanisms to regulate the functions of the added element.

In this article, Luria provided an overview of the state of knowledge of viruses and how they replicate. Though he accepted Oswald Avery's proof that DNA was the "transforming principle" in bacteria, here he suggested that the protein component of viruses, rather than DNA, might have the primary role in replication. Luria later explained to historian Horace Judson that this oversight was primarily due to his "not thinking biochemically," adding that "I don't think we attached great importance to whether the gene was protein or nucleic acid." Luria noted that James Watson and Francis Crick's work on the structure of DNA in the early 1950s permanently settled the question.

Shortly after arriving in the United States, Luria was able to secure a position in a lab at Columbia University, where he worked primarily with Frank Exner. At the time, Exner was building a million-volt x-ray machine for use in his research. This article was a result of the collaboration between the two scientists in which they utilized Exner's machine to analyze bacteriophages.

Mutants exb of Escherichia coli are insensitive to colicin B and excrete into their culture media a material that inhibits colicin activity and that appears to be the bacterial lipopolysaccharide.