13. How do fungi reproduce (describe two ways)? Why is pseudohyphal growth dange

Question

13. How do fungi reproduce (describe two ways)? Why is pseudohyphal growth dangerous in a clinical setting? Explain the functions of the two types of hyphae. Are fungi macroscopic or microscopic? Explain.

14. How are bacteria, fungi, algae, protozoa and viruses both friends and foes of humans? Give specific examples of how all of these microbes affect our daily lives.

15. In the “Case of the sick sophomore”, what information might help distinguish between the eukaryotic culprits of Cryptococcus and Toxoplasma?

16. What kind of microbe causes toxoplasmosis? How is it transmitted? Describe the symptoms and treatment of this disease. How common is it?

Explanation / Answer

13. Fungi reproduce through Sexual, Asexual, and vegetative methods

Vegetative reproduction: Most commonly occurs through fragmentation. The hypha breaks up into small fragments. Each fragment develops into a new individual. Fission, budding. Sclerotia, rhizomorphs are all different modes of vegetative reproduction

Budding commonly occurs in unicellular yeasts.

Asexual reproduction: It occurs through formation of spores. Fungal spores are of diverse types and are borne on special structures called sporophores. Asexual spores are uninucleate and nonmotile. Conidiospores, sporangiospores are examples.

Sexual reproduction occurs when two different mating types of mycelium come close together. Plasmogamy occurs, leads to formation of a dikaryote. It is followed by karyogamy where the two haploid nuclei fuse. Meiosis occurs then, which gives rise to gametes of different mating types. The gametes are disseminated into the environment.

Pseudohyphal growth results in malnutrition of the affected individual. The fungi attaches to the tissues and absorbs all the nutrients. It establishes a chronic infection and cannot be treated easily.

Fungi are either septate or aseptate. Septate hyphae form cross walls that clearly separate each cell. Nonseptate hyphae lacks the cross walls and has many nuclei in a single cell.

Both microscopic and macroscopic fungi exist. Yeasts are microscopic, molds like rhizopus, penicillium, and mushrooms are visible to naked eye.

14. Bacteria, fundi, algae, protozoa, all are essential in biogeochemical cycling. They are required for nutrient cycling. Algae are primary producers in oceans and are largest producers in the water ecosystems.

Bacteria are used to ferment alcohol, prepare cheese, yogurt, antibiotics, enzymes, and so on. Fungi are used for fermentation of breads, wine, production of enzymes, and pharmacologically active components like vitamins, amino acids. Protozoa play an important role in water ecosystems and in waste water treatment.

15. Cryptococcus have cell walls, they are covered with thin layers of capsule.They are generally round to oval shaped and appear smaller in size. Toxoplasma are relatively larger, they lack a cell wall, they are motile

16. Toxoplasmosis is caused by a protozoan parasite called Toxoplasma gondii. It is transmitted through uncooked and under cooked meats, from rodent animals to humans, and from mother to child.The parasites infect Red blood cells and reproduce there. They repeat their lifecycles in RBC leading to lysis of large number of RBC. Affected person becomes anemic. The toxins of the parasite cause fevers. Toxoplasma infects about 22% of Americans. The disease automatically resolves in few days in most of the individuals. In a few individuals, antihelminthic drug administration is required.

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