Effects of Environment on the Composition of Bacterial Cells

Abstract

The manufacture of enzymatic proteins, ribonucleic-acid (RNA), deoxyribo-nucleic-acid (DNA), cell wall, lipid carbohydrate,and yolutin granules can proceed independently of each other for greater or lesser periods. Nevertheless, in each environment which supports sustained (and therefore balanced) growth, a bacterial cell produces each of its chemi-cal components in predictable and invariant proportions to the others. The formation of each cellular component is governed by controls which coordinate syntheses and thereby insure the orderliness on which balanced growth depends. Furthermore, these controls do not commit the cell to a rigid pattern of biosynthesis; rather, they permit selective expansion of different functions in different environments. The requirement of amino acids for RNA synthesis explains how RNA might be made at a rate exactly appropriate for protein synthesis, and the re-quirement of protein synthesis to initiate DNA replication explains how a new cell is guaranteed a proper endowment of DNA. Many environ-mentally induced alterations in the chemical composition of bacteria appear to constitute adaptive responses of the cell''s regulatory mecha-nisms.