Chapter 34

Summary		Questions		Media Resources
34.1 Bacteria are the smallest and most numerous organisms.
• Bacteria are the oldest and simplest organisms, but they are metabolically much more diverse than all other life-forms combined. • Bacteria differ from eukaryotes in many ways, the most important of which concern the degree of internal organization within the cell.		1.  Structural differences among bacteria are not great. How are different species of bacteria recognized? 2.  In what seven ways do prokaryotes differ substantially from eukaryotes?		•Enhancement Chapter: Extremophilic Bacteria
34.2 Bacterial cell structure is more complex than commonly supposed.
• Most bacteria have cell walls that consist of a network of polysaccharide molecules connected by polypeptide cross-links. • A bacterial cell does not possess specialized compartments or a membrane-bounded nucleus, but it may exhibit a nucleoid region where the bacterial DNA is located.		3.  What is the structure of the bacterial cell wall? How does the cell wall differ between gram-positive and gram-negative bacteria?		•Characteristics of Bacteria
34.3 Bacteria exhibit considerable diversity in both structure and metabolism.
• The two bacterial kingdoms, Archaebacteria and Eubacteria, are made up of prokaryotes, with about 5000 species named so far. • The Archaebacteria differ markedly from Eubacteria and from eukaryotes in their ribosomal sequences and in other respects. • Mutation and genetic recombination are important sources of variability in bacteria. • Many bacteria are autotrophic and make major contributions to the world carbon balance. Others are heterotrophic and play a key role in world ecology by breaking down organic compounds. • Some heterotrophic bacteria cause major diseases in plants and animals.		4.  How do the Archaebacteria differ from the Eubacteria? What unique metabolism do they exhibit? 5.  Why does mutation play such an important role in creating genetic diversity in bacteria? 6.  How do heterotrophic bacteria that are successful pathogens overcome the many defenses the human body uses to ward off disease?		•Bacteria Diversity • Marine Biotechnology
34.4 Bacteria are responsible for many diseases but also make important contributions to ecosystems.
• Human diseases caused by heterotrophic bacteria include many fatal diseases that have had major impacts on human history, including tuberculosis, cholera, plague, and typhus. • Bacteria play vital roles in cycling nutrients within ecosystems. Certain bacteria are the only organisms able to fix atmospheric nitrogen into organic molecules, a process on which all life depends.		7.  What are STDs? How are they transmitted? Which STDs are caused by viruses and which are caused by bacteria? Why is the cause of chlamydia unusual?		• Improving Antibiotics •Antibiotic Resistance •Making E. coli Deadly

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