Eucaryotic Cells and Microbes Chapter 5 Eucaryotic Cells and Microbes

I. Origin of the Eucaryotic Cell A. Recall: A eucaryotic cell has a true nucleus. B. Oldest eucaryotic fossils are about 2 billion years old. C. Endosymbiotic theory of Dr. Lynn Margulis: this theory states that mitochondria and chloroplasts were once free-living bacteria that entered into a symbiotic relationship with an ancestral eucaryotic cell.

II. Common Eucaryotes Studied in Microbiology A. Fungi: Kingdom Mycetae (Fungi) B. Algae: different new Kingdoms K. Stramenopila-Golden and Brown algae C. Protozoa: various new Kingdoms D. Parasitic Worms(Helminthes) : K. Animalia

A. Kingdom Mycetae (Fungi) 1. The study of fungi is called mycology. 2. Most fungi are beneficial!! 3. There are more than 100,000 species, only about 100 are pathogenic for humans, and about 25 cause fatal disease. Thousands are plant pathogens! 4. Unicellular forms: yeasts: multicellular forms: molds, mushrooms, puffballs.

5. A comparison of Fungi and Eubacteria: Fungi Eubacteria Cell type Eucaryotic Procaryotic Cell memb. Sterols Sterols absent Cell wall Chitin Peptidoglycan Spores Repro. Not reproductive

6. Beneficial Aspects of Fungi: A. Primary decomposers of hard plant parts because they have enzymes called cellulases and pectinases. B. Source of Antibiotics e.g. penicillin from Penicillium notatum. C. Direct food source or used in food Production.

7. Mode of Nutrition: A. Fungi are heterotrophic; they obtain food by absorption. B. Parasitic or Saprobes C. Energy source is Carbon compounds. D. Optimal temperature : 20 -35 C E. Fungi do not have chlorophyll, no photosynthesis F. pH range: optimal about 5.5; range 2.2 - 9.6

8. Media for Fungal Growth A. Sabouraud’s agar (glucose yeast) B. Sheep blood agar C. Cornmeal agar

9. Structure of Fungi: two groups, the unicellular forms or yeasts and the multicellular forms. A. Yeasts : 1. unicellular forms may be spherical or oval. May form pseudohyphae or short chains of budding cells. 2. Reproduction by budding; some fission. 3. If denied oxygen, they ferment carbohydrates to produce ethanol and carbon dioxide useful for baking or brewing. 4. Identification: biochemical tests.

B. Multicellular Forms: Molds, Fleshy Fungi 1. Composed of filaments called hyphae. Most hyphae contain cross walls called septa, forming septate hyphae which have the appearance of cell-like units. If no septa, then they are called non-septate or “coenocytic” hyphae. 2. Hyphae grow into a mass called the mycelium, the “body” of the fungus. Two types of mycelium are a) vegetative - absorb nutrients and b) aerial--bear reproductive spores. 3. Identification: by colony characteristics, spore formation, physical appearance of mycelia or cells.

10. Reproduction of Multicellular Forms: by sexual or asexual spores. A. Asexual spores: 1. Sporangiospores 2. Conidiospores 3. Arthrospores 4 Chlamydospores 5. Blastospores B. Sexual spores: Zygospores, ascospores, basidospores.

11. Fungal Diseases A. May occur due to lowered resistance, antibiotic therapy, immunosuppression. B. Fungal infections of the skin are called dermatomycoses. E.g. ringworm. Ringworm of the scalp--Tinea capitis, caused by Tricophyton or Microsporum.Tinea pedis (athlete’s foot)-Trichophyton. C. Candidiasis: infection caused by yeast, Candida albicans.

D. Histoplasmosis: caused by Histoplasma capsulatum D. Histoplasmosis: caused by Histoplasma capsulatum. Widespread fungal infection in the U.S. population. Not everyone shows symptoms; only about 25-100 die of this out of 500,000 new infections a year. Usually spontaneous recobvery, otherwise use amphotericin B E. Pneumocystis pneumonia: caused by Pneumocystis carinii, most common cause of death in AIDS patients.

F. Ergotism or Ergot poisoning: caused by Claviceps purpura. May see as black masses on rye plants. Causes convulsions, delusions. Persons accused of witchcraft may have been ill with this fungus.

G. “Sick Building syndrome”: illness associated with mold growing in homes or buildings. Stachybotrys sp. as causative agent.

H.Pityriasis versicolor: yeast infection of outer epidermis caused by Malassezia furfur.

KINGDOM MYCETAE DESCRIBED BY G.C. AINSWORTH IN 1973 FOUR DIVISIONS: 1. ZYGOMYCOTA 2. ASCOMYCOTA 3. BASIDOMYCOTA 4. DEUTEROMYCOTA 5. CHYTRIDIMYCOTA

ZYGOMYCOTA Saprobe molds with coenocytic hyphae Some are human pathogens, mainly opportunistic. May also be found in fish and aquatic plants. They can form conidia or sporangiospores. Ex. Rhizopus stolonifer, common bread mold.

2. ASCOMYCOTA 1. There are about 2000 genera. Sac fungi are the largest group and are economically important as well as biologically. 2. Their spores are called ascospores. 3. Saccharomyces cerevisiae is important in baking, in the wine industry, and to produce B-complex vitamins. 4. Gourmet mushrooms called “truffles” belong to the ascomycota

5. Histoplasma capsulatum causes histoplasmosis. 6. Other pathogenic genera are Aspergillus and Microsporum. 7. Microsporum may cause ringworm.

3. BASIDIOMYCOTA Called the “club fungi”; they produce sexual basidospores. They include the mushrooms, toadstools, puffballs, rusts, smuts, and bracket fungi. Agaricus, the commercial mushroom, is the only food crop of economic importance here. Most are non-pathogens but can cause economic loss.

The yeast, Cryptococcus neoformans, is the one human pathogen in this group and it may be problematic for AIDS patients.

4. DEUTEROMYCOTA “Fungi Imperfecti” because they have not been found to produce sexual spores. This classification acts as a “holding” category until sexual spores are observed, then the fungus is re-classified. This group contains many of the human fungal pathogens, e.g. Candida

LICHENS These are a symbiotic relationship between an alga and a fungus. The alga can be the blue-green alga(cyanobacterium) or green algae; the fungus is usually from the division Ascomycota. There are about 25,000 species of lichens. The alga contributes nutrients and the fungus contributes protection.

Lichens serve as a food for the arctic caribou. Lichens are used to make litmus paper. Some lichens produce antibiotics. Lichens are sensitive to certain atmospheric components and recently have been used to moniter air pollution.

SLIME MOLDS These are now classified in Kingdom Amoebozoa There are saprobes and parasitic forms. They are divided into two groups:1)cellular slime molds and 2)acellular slime molds. The acellular forms are masses of protoplasm referred to as “slugs” or “plasmodia”.