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..)