Bacterial Growth, Genetics, and Virulence

Chapter 7

Bacterial Growth, Genetics, and Virulence

Proliferation of Bacterial Cells

Bacterial growth curve

Growth requirements

1. Overview

2. Oxygen requirement

3. Nutrient requirements

4. Temperature requirements

Cell division

Bacterial spores (endospores)

• Spores, formed by some gram-positive bacteria, represent a dormant state that is resistant to heat, drying, and chemicals.

1. Spore formation, a variant type of cell division, is induced by depletion of essential nutrients needed for normal growth.

2. Germination of spores into vegetative cells is initiated by damage to the spore coat by trauma, water, or aging and requires specific nutrients.

II Bacterial Genetics

• Important definitions are given in Table 7-1.

Bacterial chromosome

1. Single, double-stranded, circular molecule of DNA, containing about 5 million base pairs (or 5000 kilobase pairs)

2. Operons provide coordinated control of protein-coding (structural) genes. A bacterial chromosome contains many operons.

• The enzymes in many bacterial metabolic pathways are encoded by polycistronic operons, which contain multiple structural genes.

• All the genes in a polycistronic operon are transcribed as a unit, producing a single messenger RNA (mRNA) that is translated into multiple proteins.

• Transcription of the lac operon and many other operons is controlled by presence or absence of metabolites to meet the needs of the cell (Fig. 7-2).

Other genetic elements

1. Plasmids

2. Bacteriophages

3. Transposons

• DNA sequences (“jumping genes”) that can move from one position to another in a bacterial chromosome or between different molecules of DNA. These elements lack a replication origin.

Jun 18, 2016 | Posted by in IMMUNOLOGY | Comments Off on Bacterial Growth, Genetics, and Virulence

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