Eukaryotic microorganisms

• Fungi
• Protozoa
• Algae

General characteristics

• Contain nucleus and organelles
• Reproduction: sexual or asexual
• Cells larger than prokaryotes
• Most have cell walls
• Complex morphology
• Heterotrophic nutrition
• Can be saprophytes or parasites
• Prefer mesophilic temperatures, low pH and low water activity
• Classification: morphology and life cycle
• Can produce mycotoxins
• Can cause airborne, foodborne and skin infections
• Commercially important:
• Growth and rotting of fruits and vegetables
• Biological control of insects
• Alcohol from starch
• Enzymes: protease, amylase, pectinase, lipase
• Organic acids: citric acid, fumaric acid
• Steroids
• Soy sauce

 

• Unicellular with flagella at some stage in life cycle
• Septate or coencytic hyphae
• Absorptive nutrition
• Habitat: aquatic or moist environments
• 4 classes (Chytridiomycetes, Hyphochytridiomycetes, Plasmodiophoromycetes, Oomycetes
• Saprolegnia parasitica: diseases in fish
• Phytophthora infestans: potato blight

• Most familiar and common fungi
• Non motile
• Absorptive nutrition

• Coencytic hyphae
• Zygospores produced during sexual cycle
• Habitat: soils or decaying vegetation
• Rhizopus stolonifer: Common bread mould

• Ascospores produced in a sac-like (asci) structure during sexual cycle
• Include both unicellular (yeasts) and septate mycelia
• Habitat: soils or decaying vegetation
• Able to break down a wide range of substrates
• Important industrially, medically and ecologically
• Food spoilage
• Industrial fermentations
• Claviceps purpurea: Hallucinogenic alkaloids (LSD)
• Ergotism: disease from infection of cereal grains
• Trichophyton spp.: Athletes foot, tinea and ringworm
• Saccharomyces cerevisiae: alcoholic beverages and bread manufacture (brewers and bakers yeast)

• Basidiospores produced on the outside of a club-like (asci) reproductive structure during sexual cycle
• Septate hyphae
• Habitat: soils, decaying plants or other organic matter
• Agaricus spp.: mushrooms
• Wood-rot fungi

• Only have asexual life cycle
• Reproduction by hyphal fragmentation or conidia formation
• Septate hyphae
• Habitat: soils, decaying plants or animal surfaces
• Penicillium chrysogenum: penicillin
• Histoplasma capsulatum: histoplasmosis
• Aspergillus flavus: aflatoxins
• Candida albicans: candidiasis

• Similar to fungi and protozoa at different stages of growth

Acellular slime moulds
        Multicellular wall-less masses of protoplasm with many nuclei (plasmodia)
        Form fruiting bodies in the sporulation stage
 
 
 

4. Protozoa

General characteristics

• Single celled
• Contain nucleus and organelles
• Most have animal-like characteristics
• No rigid cell walls
• Reproduction: sexual or asexual
• Cells larger than prokaryotes
• Heterotrophic or autotrophic nutrition
• Free living inhabitants of waters and soils or parasites
• Classification: locomotion and structural features

1. Flagellates (Mastigophora)

• Either plant-like or animal-like
• Possess flagella
• Can be free-living in waters, soils or parasites of living hosts
• Zooflagellates or phytoflagellates
• Zooflagellates
• Cells ovoid to elongated
• Reproduce by longitudinal binary fission
• Giardia lamblia: giardiasis
• Trichomonas hominis: diarrhea
• Trichomonas vaginalis: trichomoniasis
• Trypanosoma spp.: African sleeping sickness and Chagas disease
• Leshmania spp.: Kala-azar, skin diseases

• Protoplasm: membrane, cytoplasm and nucleus
• Change shape
• Motile by pseudopodia
• Reproduce by binary fission
• Some form cysts
• Entamoeba histolytica: amoebic dysentery

• Spore-forming stage in life cycle
• Both sexual and asexual reproduction
• Parasites of animals
• Non-motile
• Require dissolved nutrients
• Toxoplasma gondii: toxoplasmosis
• Plasmodium spp.: malaria
• Cryptosporidium: severe diarrhea

4. Ciliates (Ciliophora)

• Contain cilia on surface
• Possess mouth (cytostome) and ingest nutrients
• Nuclei: macronucleus (growth) and micronucleus (sexual reproduction)
• Widely distributed in waters and moist soils
• Balantidium coli: dysentery

General characteristics

• Single or multi-cellular
• Contain nucleus, chlorophyll a and organelles
• Phototrophs and mostly autotrophic nutrition
• Most have rigid cell walls
• Mainly motile
• Absorb dissolved nutrients
• Reproduction: sexual or asexual
• Cells larger than prokaryotes
• Classification: morphology, pigments, storage products, flagella, cell wall
• Problems: blooms, clogging, toxins
• Beneficial extracts: thickening agents, emulsifiers, anti-inflammatory drugs, agar

• Mostly fresh water, some marine
• Uni and multi-cellular
• Pigments: chlorophyll a, b and carotenoids
• Cell wall: cellulose and pectin
• Food storage: starch
• Genera: Chlamydomonas, Chlorella

• Marine habitat
• Multicellular and macroscopic
• Pigments: chlorophyll a, c and carotenoids
• Cell wall: cellulose and alginates
• Food storage: laminarin and fat

3. Red algae (Rhodophyta)

• Mostly marine habitat
• Multicellular and macroscopic
• Pigments: chlorophyll a and phycobilins, carotenoids
• Cell wall: cellulose and pectin
• Food storage: starch

4. Diatoms (Chrysophyta)

• Mostly marine habitat
• Unicellular, wide variety of shapes
• Pigments: chlorophyll a, c and carotenoids
• Cell wall: pectin and silica
• Food storage: chrysolaminarin and oils

5. Dinoflagellates

• Marine and freshwater habitats
• Unicellular with two flagella
• Morphologically diverse
• Heterotrophic or autotrophic
• Often bioluminescent
• Can produce toxins
• Pigments: chlorophyll a, c and carotenoids
• No cell wall
• Food storage: starch and oils

6. Euglenoids

• Freshwater habitats
• Unicellular with two flagella
• Morphologically diverse
• Heterotrophic or autotrophic
• Can ingest nutrients
• Pigments: chlorophyll a, b and carotenoids
• No cell wall
• Food storage: paramylon and oils