Contrast the size of the single chromosome in bacteriophage and T2 with that of E. coli. How does this relate to the relative size and complexity of phages and bacteria?

Key Concepts

Chromosome Structure in Bacteriophages and E. coli

Bacteriophages, such as T2, typically possess a single, linear or circular chromosome that is much smaller than the chromosomal DNA found in E. coli. E. coli has a single, circular chromosome that is approximately 4.6 million base pairs long, while T2's genome is about 170,000 base pairs. This difference in chromosome size reflects the simpler genetic requirements of phages compared to bacteria.

Genetic Complexity and Function

The genetic complexity of an organism is often correlated with its size and the number of genes it possesses. Bacteriophages, being simpler entities, have fewer genes that primarily encode proteins necessary for infection and replication within a host. In contrast, E. coli has a more complex genome that encodes a wider array of proteins for metabolism, replication, and cellular functions, reflecting its status as a living organism.

Phages vs. Bacteria: Size and Complexity

Phages are generally much smaller than bacteria, both in size and genetic content. This size difference is indicative of their roles; phages are obligate parasites that rely on bacterial hosts for replication, while bacteria are independent organisms capable of metabolism and reproduction. The relative simplicity of phages allows them to efficiently hijack bacterial machinery, whereas bacteria must maintain a more complex set of functions to survive and thrive in various environments.