Eukaryotic Microbial Diversity

1Eukaryotic 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.

2Eukaryotes 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

3Microbial 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

4Kingdom 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

5Plant-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

6Fungus-like • Water molds• Slime molds

http://en.wikipedia.org/wiki/Slime_mold

Animal-like protists

Capable of ingesting their food.

Found among many different groups, so not good for taxonomy.

http://ar.geocities.com/seti_argentina/estamos_solos/ameba.jpg

7How 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

8Classification 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

9Protozoa

• 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

10Some 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

11Algae

• 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

12Water 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.

13Fungi

• 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

14Fungi 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

15Impacts 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)

16Classification 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.

Evolution of the fungiEvolution of the fungi

Classification & Phylogeny

motile spores

zygosporangia

ascibasidia

FungiFungiClassification of fungal diseases (mycoses)Classification of fungal diseases (mycoses)

Superficial, cutaneous, subcutaneousSuperficial, cutaneous, subcutaneousSystemic and opportunisticSystemic and opportunisticPoisoning and allergiesPoisoning and allergies

TreatmentTreatmentAzole drugs, amphotericin B, othersAzole drugs, amphotericin B, others

Opportunistic infectionsOpportunistic infections AspergillusAspergillus (aspergillosis) (aspergillosis)

Variety of species, very common in soil, plant Variety of species, very common in soil, plant materialsmaterials

Serious infections in immunocompromisedSerious infections in immunocompromised Allergies to Allergies to A. fumigatusA. fumigatus Poisoning from aflatoxin from Poisoning from aflatoxin from A. flavusA. flavus

CandidaCandida (candidiasis)- normal microbiota (candidiasis)- normal microbiota Cause of vaginal infections, diaper rash, thrushCause of vaginal infections, diaper rash, thrush Capable of infecting any part of the bodyCapable of infecting any part of the body Dangerous in cancer patients, HIV infections, etc.Dangerous in cancer patients, HIV infections, etc.

Opportunists-2Opportunists-2Cryptococcus neoformansCryptococcus neoformans

Inhalation of sporesInhalation of sporesCan infect many parts, but has predilection for Can infect many parts, but has predilection for

CNSCNSParticularly serious in AIDSParticularly serious in AIDS

Pneumocystis cariniiPneumocystis cariniiVery protozoan like, but is a fungusVery protozoan like, but is a fungusMost cases associated with AIDSMost cases associated with AIDSSerious lung infections: PCP (Serious lung infections: PCP (P. cariniiP. carinii pneumonia) pneumonia)

22Microbes 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?

23Microbes 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..)