Eukaryotic Microbial Diversity

1. Eukaryotic Microbial Diversity • Early attempts at taxonomy: all plants and animals • Whitaker scheme (late 20th century) • Five kingdoms • Modified by Woese’s work on rRNA • Three Domains, one of which is Eukaryotes • Protista: the grab bag Kingdom • Always recognized as a highly diverse group • In new schemes, split into 7 kingdoms • Since the application of molecular biology, taxonomy of all things constantly changing.

2. Eukaryotes vs. prokaryotes • Eukaryotes are larger • Eukaryotes have membrane-bound organelles • Nucleus, mitochondria, membrane systems • Larger size requires functional compartments • Mitochondria once bacteria? So same size! http://www.earthlife.net/images/eury-cell.gif

3. Microbial eukaryotes • Animals • Parasitic worms; studied by Parasitologists • Fungi • Yeasts and molds, studied by Mycologists • Several types can cause human disease • Protists • Unicellular eukaryotes with many different characteristics. Also studied by Parasitologists. • Some cause human disease • Plants: not of particular interest other than hosts

4. Kingdom Protista • Highly diverse group of organisms • Size range from 5 µm to several meters (kelp) • Defined more by what they aren’t • Nutrient/energy acquisition ranges from photosynthesis to predatory to detrivores • Important in many food webs • Provide link between bacteria and larger organisms library.thinkquest.org/ 12413/protist.html

5. Plant-like Protists • Contain chloroplasts • Representatives • Diatoms (right). • Diatomaceous earth = fossilized diatoms: abrasives and slug repellants. • Red, brown, yellow algae • Seaweed, source of agar • Dinoflagellates • Neurotoxins and red tide http://www.bhikku.net/archives/03/img/diatoms.JPG www.enviroliteracy.org/ article.php/534.html

6. Fungus-like • Water molds • Slime molds Animal-like protists Capable of ingesting their food. Found among many different groups, so not good for taxonomy. http://en.wikipedia.org/wiki/Slime_mold http://ar.geocities.com/seti_argentina/estamos_solos/ameba.jpg

7. How to classify? • Cell ultrastructure and molecular analysis becoming the main methods used for classification. • Suggests that several kingdoms would be appropriate. • Alternative scheme, keep the kingdom Protista, classify protozoa into several phyla • Typical textbook: • 4 groups of protozoa • Algae • Slime molds • Water molds

8. Classification of Protozoa Alveolates Ciliates Apicomplexans Dinoflagellates Amoebae Shelled and unshelled Euglenozoa Ameobae Euglenoids Kinetoplastids Archaezoa Diplomonadida Parabasala http://www.jracademy.com/~mlechner/archive1999/paramecium.JPG

9. Protozoa • What are the characteristics of Protozoa? • Unicellular eukaryotes • Lack a cell wall • Require moist environments (water, damp soil, etc) • Great amounts of diversity • Locomotion: float, cilia, flagella, pseudopodia • Nutrition: chemoheterotrophs, photoautotrophs, either • Simple to complex life cycles, reproduction • Different cell organelles, some lack mitochondria

10. Some protozoal terminology • Cyst: a resting stage similar to a spore with a thick wall and low level of metabolism. • Trophozoite: stage in life cycle during which the microbe is feeding and growing. • Merozoite: Small cells with a single nuclei produced during schizogony. • Large, multinucleated cell undergoes cytokinesis to produce multiple daughter cells (merozoites) • Cytoplasmic streaming. • Cytoskeleton aids extension of cell membrane

11. Algae • Green algae • Ancestors of plants • Red algae • Mostly marine • Source of food thickeners carrageenan and agar • Chrysophyta (golden algae, diatoms, etc) • Diatoms: major component of phytoplankton • Diatomaceous earth as abrasives, gardening tools • Brown algae • Common seaweeds, kelps http://habitatnews.nus.edu.sg/news/chekjawa/ria/photos/r119.jpg

12. Water Molds and Slime Molds • Water molds • Similar to fungi except for 4 major differences; • 2 of 4: cellulose, not chitin in cell wall; motile spores • Phytophthora: Irish potato blight, sudden oak death • Slime molds • Acellular slime molds: The Blob, giant multi-nucleated cell; reproduces into amoebae that are amphibious • Cellular slime molds, e.g. Dictyostelium: unicellular, aggregate into slug-like structure, model for primitive development and differentiation.

13. Fungi • Mycology: the study of fungi • Fungi are mostly saprophytes, all heterotrophs • Saprophytes: decay non-living organic matter • Fungi are the kings of decomposition • Heterotrophs: use pre-formed organic matter • Not autotrophs, not photosynthetic • Fungi grow into, through their food • Release extracellular enzymes, break down polymers into LMW compounds for transport

14. Fungi terminology and structure • Hypha (singular) hyphae (plural): thread • Hyphae may be partially separated into cells or not at all (ceonocytic). • Cytoplasm is continuous throughout hypha • Mycelium (plural mycelia): a mass of hyphae • Like a bacterial colony except really all one organism. • Some fungi are molds, some are yeasts • Yeasts are oval, unicellular • Dimorphic: able to grow as either form. • Typical of some disease-causing fungi

15. Impacts of Fungi • Disease: mycosis (plural mycoses) • Superficial (on hairs, nails) • Cutaneous (dermatophytes, in skin (athlete’s foot) • Subcutaneous (deeper into skin) • Systemic (in deeper tissues, usually via lungs) • Opportunists: serious disease when immune system is depressed. • Antibiotic production • Penicillium, Cephalosporium • Decomposition; Food industry (soy sauce)

16. Classification of fungi • By sexual reproductive structures • Fungi reproduce both asexually and sexually • Deuteromycota = Fungi Imperfecti • No longer a valid classification • Contained fungi that couldn’t be coaxed into having sex • Through morphological and molecular means (e.g. DNA analysis), being distributed into the other 3 phyla of fungi.

17. Evolution of the fungi

18. asci basidia zygosporangia Classification & Phylogeny motile spores

19. Fungi Classification of fungal diseases (mycoses) Superficial, cutaneous, subcutaneous Systemic and opportunistic Poisoning and allergies Treatment Azole drugs, amphotericin B, others

20. Opportunistic infections Aspergillus (aspergillosis) Variety of species, very common in soil, plant materials Serious infections in immunocompromised Allergies to A. fumigatus Poisoning from aflatoxin from A. flavus Candida (candidiasis)- normal microbiota Cause of vaginal infections, diaper rash, thrush Capable of infecting any part of the body Dangerous in cancer patients, HIV infections, etc.

21. Opportunists-2 Cryptococcus neoformans Inhalation of spores Can infect many parts, but has predilection for CNS Particularly serious in AIDS Pneumocystis carinii Very protozoan like, but is a fungus Most cases associated with AIDS Serious lung infections: PCP (P. carinii pneumonia)

22. Microbes and diseases: what to study-1 • 1. Causative microbe: name, morphology (shape, size, Gram stain, etc.), physiology (aerobe, anaerobe, etc) and some info on classification (what's it related to?) • 2. Pathogenesis and clinical disease:  what disease does it cause (signs and symptoms) and how does it do it (capsule, toxins..)? • 3. Transmission and epidemiology: how do you get the disease?

23. Microbes and diseases: what to study-2 • 4. Diagnosis: How does the lab usually identify the causative agent? • 5. Treatment: antibiotics prescribed (or not- no cell wall, no penicillin) or other treatment (oral rehydration therapy for cholera). • 6. Prevention and control (stop the spread; condoms, kill urban rats..)