List and discuss five structures in bacteria that allow them to cause disease
What will be an ideal response?
1. Capsules: Many bacteria are surrounded by a capsule, which is typically composed of
polysaccharides. The capsule protects the bacterium from the host animal's immune
system. For example, Streptococcus pneumoniae strains that are encapsulated can cause
pneumonia, while those without capsules are nonvirulent.
2. Pili: Pili are short protein appendages found in a number of bacteria. These help bacteria
to bind to animal cells. Neisseria gonorrhoeae, which causes gonorrhea, has pili that allow
it to attach to cells of the throat, eye, urogenital tract, or rectum in humans.
3. Exotoxins: A number of bacterial lineages produce exotoxins. These are toxic proteins
that are secreted from the bacterium and which interfere with the biochemical processes of
body cells in various ways. For example, the botulinum exotoxin causes muscle paralysis
by interfering with the transmission of nerve impulses.
4. Endotoxins: Gram-negative bacteria can cause disease through endotoxins, which are
lipopolysaccharides released from the outer membrane when bacteria die and lyse.
Endotoxins cause disease by overstimulating the host's immune response, often triggering
inflammation.
5. Exoenzymes: Some bacteria release exoenzymes, which are catalytic proteins. These may
breakdown cell membranes (causing cells to rupture), collagen (causing connective tissue
disorders), red and white blood cells (leading to anemias and weakening of the immune
system). Bacteria that release exoenzymes include Streptococcus and Clostridium.
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Which of the following genera has proved useful for manipulating plant cells?
A. Escherichia B. Bacillus C. Pseudomonas D. Agrobacterium
Which event can introduce a protein domain into a pre-existing protein?
a. gene alignment b. intron shuffling c. exon shuffling d. peptide shuffling e. exon splicing
Molecular relationships and other studies have allowed for many conidial fungi to be reclassified into a
fungal phylum. Most of these reclassified conidial fungi have turned out to belong to which fungal phylum?
a. Glomeromycota b. Basidiomycota c. Chytridiomycota d. Zygomycota e. Ascomycota
Life forms exhibit both unity and diversity. Which of the following best demonstrates the unity among all organisms?
A. The three domains of life. B. Emergent properties. C. Amino acids are the building blocks of proteins. D. Natural selection.