Growth of bacteria is accomplished by an orderly progress of metabolic processes fol-lowed by cell division by binary fission. Therefore, growth requires three complex processes: metabolism, which produces cell material from the nutrient substances pres-ent in the environment; regulation,which coordinates the progress of the hundreds of independent biochemical processes of metabolism to result in an orderly and efficient synthesis of cell components and structures in the right proportions; and cell division, which results in the formation of two independent living units from one.
We do not review in depth the many aspects of (mostly mammalian) metabolism custom-arily learned in biochemistry courses. Many of the principles, and even some of the details of metabolism, are universal. Indeed, the principle known as the unity of bio-chemistry is underscored by the fact that much of what we know of metabolic pathwaysis derived from work with Escherichia coli. We focus, rather, on the unique aspects of bacterial metabolism that are important in medicine.
The broad differences between bacteria and human eukaryotic cells can be summa-rized as follows:
1. The metabolism of most bacteria is geared to rapid growth and proceeds 10 to 100 times faster than in cells of our bodies.
2. Bacteria are much more versatile than human cells in their ability to use various com-pounds as energy sources and in their ability to use oxidants other than molecular oxygen in their metabolism of foodstuffs.
3. Bacteria are much more diverse than human cells in their nutritional requirements, be-cause they are more diverse with respect to the completeness of their biosynthetic pathways.
4. The simpler prokaryotic body plan makes it possible for bacteria to synthesize macro-molecules by far more streamlined means than our cells employ.
5. Some biosynthetic processes, such as those producing murein, lipopolysaccharide (LPS), and teichoic acid, are unique to bacteria.
Each of these differences contributes to the special nature of the human – microbe en-counter, and each provides a potential means for designing therapeutic agents to modify the outcome of this interaction.
Bacterial metabolism is highly complex. The bacterial cell synthesizes itself and gen-erates energy for active transport, motility (in some species), and other activities by as many as 2000 chemical reactions. These reactions can be helpfully classified according to their function in the metabolic processes of fueling, biosynthesis, polymerization, and assembly.