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Unformatted text preview: Topic 5 Fundamentals of Microbiology (Biology 140) Course notes Dr. Josh D. Neufeld Learning Objectives: Following this topic, you should have an understanding of how bacteria are cultured and the difference between defined and complex growth media. You should also appreciate the mechanism of cell division in bacteria. Before we learn about cell growth, it is necessary to briefly consider metabolism and nutrition. For cells to grow, they must convert chemical compounds into cellular matter. Nutrients from outside the cell are transformed into new cell material. This process is called anabolism or biosynthesis. The cell requires energy for biosynthesis, as well as for other processes (e.g. transport, motility). Energy is often derived from the oxidation of chemical compounds, in a process called catabolism. We will not cover Chapter 5 in detail at this point in the course. Many of you will already be familiar with some of the material in Chapter 5 from some other courses. Please review this material if needed. The first diagram in the lecture slides presents a simplified overview of cell metabolism. This diagram should help you to understand the relationship between catabolism and anabolism. Culture Media • Defined: the exact chemical composition is known  ­ ­ purified ingredients are used. Complex: the exact chemical composition is not known. • See Table 5.4 for a good demonstration of the different nutritional requirements of different bacteria. The microbiological concept of growth really refers to increase in cell number. This is achieved by division of a single cell into two new cells. Figure 6.1 illustrates the process of binary fission. An important thing to consider is how cell wall synthesis takes place. This is illustrated in Figures 6.2, 6.3, 6.5 ­6.7. During cell growth, the peptidoglycan layer must be opened up as new peptidoglycan is being deposited. The dissacharide pentapeptide is transported to the periplasm from the cytoplasm by the lipid carrier bactoprenol, and inserted into the growing cell wall. The next step, transpeptidation, in which the peptide cross ­links in the peptidoglycan are formed, is the target of penicillin. ...
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