Lecture 3-4 - Prokaryotes and Fungi

Question 1

Compare and contrast between Bacteria and Archaea.

Answer 1

Both:

• Prokaryotes
• Lack membrane bound organelles and cytoskeleton

Differ:

• Cell wall composition: Peptidoglycan present in bacteria, not present in Archaea
• rRNA sequences (different ribosomes)
• phospholipid composition(ether bonds in archaea, ester in bacteria)
• Bacteria sensitive to toxins and antibiotics

Question 2

Describe the characteristics of an Archaea.

Answer 2

• Consist of a small genome

- Unique membrane structures (can be monolayer/bilayer, ether linkage between phosphate and fatty acids)

Question 3

Bacteria reproduce asexually through binary fission. Explain four methods where Bacteria can obtain genetic diversity.

Answer 3

1. Mutation
2. Conjugation: exchanging of genetic material (unidirectional) through a sex pilus.
3. Transformation: bacterial chromosome form dead bacterial cells is integrated to a live bacteria’s genome
4. Transduction via bacteriophage: Bacteriophage infects donor bacterium, in which the bacterial DNA is accidentally packaged into a phage. The phage then infects another bacteria, integrating the donor DNA to the new bacterium.

Question 4

Mention the four common shapes of bacteria.

Answer 4

Cocci, Bacilli, filamentous, spiral

Question 5

Diphtheria toxin is an example of an AB subunit toxin. Explain what it means.

Answer 5

The B domain of the toxin attaches to the heparin-binding receptors on the host cell. After which, the A subunit became active and attaches ADP-ribose to the EF-2. These binding inhibit all the EF-2 molecules in a cell, hence blocking protein synthesis and leading to cell death.

Question 6

Describe characteristics of a fungi.

Answer 6

• Able to grow as filaments or as yeast
• Posses a feeding (vegetative) structure called a mycelium
• Heterotrophs (Digest food externally)
• Reproduce by spores

Question 7

Mycelium is a network of _____. What is it?

Answer 7

Hyphae: monofilaments (cytoplasm in a tube) with large SA/V ratiot

Question 8

Hyphae may be divided by cross walls called _______, which are incomplete to allow __________. Hyphae can fuse in a process called _________, forming cells with mixed nuclei called ________.

Answer 8

Septa, cytoplasmic continuity, anastomose, heterokaryons

Question 9

Energy reserves in fungi are stored as ________.

Answer 9

glycogen, fats, and oils

Question 10

Mention two examples of fungal association and briefly explain.

Answer 10

Mycorrhizae:

• fungal association with plant roots.
• allow fungi to extract sugar from plant in exchange for mineral nutrients and water from the soil through the mycelia.

Endophytes:
-fungal association with leaves

Lichen:
-fungal association with algae

Question 11

Explain the reproduction process of fungi generally.

Answer 11

Reproduction occurs either through sexual/asexual spores or through budding (yeasts). In sexual reproduction, hyphae of compatible mating types undergo plamsogamy (fusion of cytoplasm), forming the heterokaryon. Then, karyogamy occurs forming the zygote (2n). It then undergoes meiosis to form sexual spores. Spores are then spread to the environment.

Question 12

Explain the characteristics of chytrids.

Answer 12

Chytrids:

• Aquatic or soil borne
• Motile zoospores
• Limited coenocytic (no regular septa) mycelium

Question 13

Explain the characteristics of zygomycetes.

Answer 13

Zygomycetes:

• coenocytic hyphae (no regular septa)
• Sexual spores called zygospores
• Asexual spores called sporangiospores
• Exp. fruit molds

Question 14

Explain the characteristics of ascomycetes.

Answer 14

Ascomycota:

• Hyphae have regular septa
• Sexual spores: ascospores
• Asexual spores: conidia
• Exp. Saccharomyces cerevisiae

Question 15

Explain the characteristics of basidiomycetes.

Answer 15

Basidiomycota:

• Vegetative hyphae are septate
• Asexual spores (Conidia) uncommon
• Sexual Spores: Basidiospores