Eukaryotic Microbes: Algae

• Eukaryotic microbes are explored in this chapter with a focus on algae, protozoa, fungi, lichens, and slime molds.

Algae

• Photosynthetic, eukaryotic organisms exist in the Kingdom of Protista.
• Phycology focuses on the study of algae.
• Algae consist of cytoplasm, a cell wall, a cell membrane, a nucleus, plastids, ribosomes, mitochondria, and Golgi bodies.
• Some algae possess a pellicle, stigma, and flagella.
• Algae share similarities with plants more than with protozoa.
• Algae range in size from unicellular to multicellular.
• They can arrange themselves in colonies or strands.
• Energy production happens through photosynthesis.
• Cellulose is present in most algae
• Varying pigments cause a diverse range of colors.

Algae Classification

Diatoms

• These are usually unicellular.
• Diatoms inhabit freshwater and seawater environments.
• Diatoms are a type of phytoplankton.
• Approximately 200 genera of diatoms are known.
• They form diamotamaceous earth.
• Diatoms show potential as drug delivery systems in medicine.
• There is nanotechnology potential.

Dinoflagellates

• These exist as unicellular, flagellated, photosynthetic organisms.
• They are phytoplanktons.
• Dinoflagellates produce oxygen.
• These are responsible for red tides.
• Dinoflagellates found in ponds are called green algae.

Desmids

• Desmids belong to a division of green algae.
• Land plants may have evolved from desmids.
• They show high symmetry and diversity in forms.
• Most are found in fresh water.
• Unicellular, desmids form filaments consisting of chains of cells.
• They store CHO in pyrenoids.
• Desmids reproduce asexually using fission.

Multicellular Algaes

• Large seaweeds like brown kelp are found in ocean shores.
• Green scum floats in ponds and on wet rocks.

Importance of Algae

• Algae serves as a food source.
• They contain iodine and other minerals.
• Algae are used as fertilizers.
• They are emulsifiers for pudding.
• Algae are stabilizers for ice cream.
• They can be gelling agents for jams.
• Algae provides nutrient media for bacterial growth.
• It is being studied for biofuels.
• They cause damage to water systems.

Medical Significance of Algae

• Prototheca causes rare human infections known as protothecosis.
• It exists in soil and enters wounds.
• This causes small subcutaneous lesions that develop into wart-like lesions.
• It has debilitating and fatal consequences in the lymphatic system.
• Algae can release phycotoxins, that are poisonous to humans and animals.
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Protozoa

• Protozoa are eukaryotic organisms are part of the Kingdom of Protista.
• Protozoology studies protozoa.
• Most protozoa are unicellular.
• They have a length ranging from 3 to 2,000 micrometers
• These cells are free-living in soil and water.
• Resemble animal cells.
• They consist of various eukaryotic structures and organelles.
• Protozoa has pellicles, cytosomes, contractile vacuoles, pseudopodia, cilia, and flagella.
• Chlorophyll isn't present.
• Protozoa consume algae, yeasts, bacteria, and smaller protozoans.

Characteristics of Protozoa

• Some live on dead and decaying organic matter.
• Cell walls are absent.
• A two-stage life cycle includes the Trophozoite and Cyst stages.

Trophozoite stage

• Motile
• Required for feeding
• Required for dividing

Cyst stage

• Non-motile

• Dormant

• Required for survival

• Some are parasites that are pathogenic.

• Protozoa can coexist through mutualistic symbiotic relationships.

Classification & Medical Significance of Protozoa

• Grouped into groups according to movement

Amebae

• Amoeboid movement via pseudopodia.
• These will surround and fuse with food particles.
• Lysosomes release digestive enzymes.
• Fluids are ingested through pinocytosis.
• Entamoeba histolytica causes amebic dysentery.

Ciliates

• Ciliates move using hair-like cilia.
• They exhibit an oar-like motion.
• These are considered most complex of all protozoa.
• Transmission to humans occurs from water contaminated with swine feces (Balantidium coli).
• Most cases are asymptomatic; some experience persistent diarrhea, abdominal pain, and perforated colon.

Flagellates

• Movement happens with of whiplike flagella.
• Kinetosome anchors flagella within cytoplasm.
• They show a wave-like motion.
• Trypanosoma brucei transmits through tsetse flies, causing African sleeping sickness.
• Trichomonas vaginalis causes trichomoniasis (STD).
• Giardia intestinalis & lambdia causes persistent diarrheal disease.

Nonmotile Protozoa

• Lacking pseudopodia, flagella, or cilia.
• They are sporozoa like Plasmodium spp. that causes malaria.
• Anopheles mosquitoes transmit malaria.
• Vectors that have fed on the blood of infected individuals transmit malaria.
• Cryptosporidium parvum causes severe diarrheal disease (cryptosporidiosis) in patients diagnosed with with AIDS.
• Oocysts in drinking water lead to 400,000 cases.
• Other nonmotile protozoa are Babesia spp. (babesiosis), Cyclospora cayetanensis (cyclosporiasis), Toxoplasma gondii (toxoplasmosis).

Fungi

• Fungi are diverse and classified across 3 kingdoms.
• Pathogenic fungi are within the kingdom of Fungi (Eumycota).
• Mycology is the study of fungi.
• Fungi live in diverse environment.
• Some can be either harmful or beneficial.
• They are responsible for the deterioration of unlikely materials.
• Include yeasts, molds, and mushrooms.
• Saprophytes are "garbage disposers" or original "recyclers."
• Fungal cell walls have chitin.
• Usually unicellular, others have a filament structure called hyphae which form mycelium or thallus.
• Hyphae can either be septate or aseptate.

Reproduction in Fungi

• Reproduction happens through budding, hyphal extension, or spore formation, (sexual and asexual spores)
• Sexual spores arise through fusion of 2 gametes (e.g., ascospores, basidiospores, and zygospores).
• Classification occurs based on sexual spores or the structures which spores are produced.
• Asexual spores are produced in sac-like structure called sporangium (sporangiospore) or from fungal component called conidiophore (conidia).
• Conidia are carried by wind and resistance can cause allergies in humans.

Fungi Classification

• Fungi are classified according to mode of sexual reproduction.

Phyla-Lower Fungi

• Zygomycotina
  • Common bread molds
  • Cause food spoilage
• Chytridiomycotina
  • Not a true fungi
  • Live in water and soil
  • Absorptive eating style
  • Cell wall has chitin

Phyla-Higher Fungi

• Ascomycotina
  • Sac fungi or ascomycetes
  • Includes yeasts like Candida species
  • Aspergillus, penicillium, and plant pathogens
• Basidiomycotina
  • Include yeasts like Cryptococcus; some skin and plant pathogens
  • The large and "fleshy fungi"
  • Live in the woods
  • Examples: mushrooms, toadstools, bracket fungi, and puffballs
• Deuteromycotina
  • Fungi Imperfecti and Deuteromycota
  • Contains undiscovered sexual form
  • Lost ability to reproduce.
  • Includes Candida albicans that causes yeast infection.

Yeasts

• Yeasts are unicellular that lacks mycelia.
• These are blastospores or blastoconidia.
• Observed through microscope.
• They reproduce through budding.
• Some form pseudohypha.
• Some have thick-walled, spore-like structures called chlamydospores.
• In soil, water, and skins of fruits and vegetables.
• Causes fermentation
• Saccharomyces cerevisiae, known as "baker's yeast", ferments sugar to alcohol under anaerobic conditions but breaks it down into carbon dioxide and water in aerobic conditions
• Leavening agent in bread production
• Good source of nutrients
• Colonies similar to bacteria in appearance
• Larger than bacteria

Moulds

• Moulds can usually be found in water, soil and food.
• These feature cytoplasmic filaments or hyphae that makes up the mycelium.
• Moulds extends above surface (aerial or reproductive hyphae).
• Some are found beneath the surface (vegetative hyphae).
• Reproduction happens through spore formation
• It can be sexually or asexually
• Microsporidia are not included.
• Chytridiomycotina are not pathogenic.
• Great commercial importance.
• Ascomycotina are found in antibiotic-producing molds.
• Produce large quantities of enzymes (e.g., amylase), citric acid, and other organic acids.

Dimorphic Fungi

• Can live as yeast or molds (dimorphism).
• Includes some that are human pathogens.
• Unicellular at 37°C
• Moulds when in mycelia form at 25°C
• Examples: Histoplasma capsulatum, Sporothrix schenckii, coccidioides immitis & Coccidioides posadii, and Blastomyces dermatitidis

Microsporidia

• New in Eumycota
• It can be an obligate intracellular parasitic fungi
• Formerly classified as protozoa
• It has a polar filament
• Includes coiled around microsporidial spore
• It extrudes filament to penetrate the recipient cell
• Then it produces spores in the cell
• Eye or GIT infections can be present

Fleshy Fungi

• Large fungi in the forests
• Examples: Mushrooms, toadstools, puffballs, & bracket fungi
• Includes a class of true fungi with mycelium
• Grows in soil or rotting log and fruiting body
• Forms & releases spores
• A lot can be delicious to eat
• Some resemble edible fungi are extremely toxic can cause liver and brain damage or even death

Medical Significance of Fungi

• Fungi variety has medical significance due to disease.
• Some kinds produce mycotoxins.
• Moulds & yeasts are called mycoses.
• Mycosis can be superficial, cutaneous, subcutaneous or systemic.
• Infection may progress through all the stages.

Superficial & Cutaneous Mycoses

• Superficial mycoses are outermost area infections.
• Cutaneous mycoses affect the dermis.
• Dermatophytes cause tinea infections like ringworm
• They are named according to the part that's infected.
• e.g. tinea pedis - athlete's foot
• Tinea unguium is also known as onychomycosis
• Tinea capitis - Scalp
• Tinea barbae - Face & neck
• Tinea corporis - trunk of the body
• Tinea crusis - groin area
• Candida albicans causes infections due to reduction in microflora.
• Candida albicans are opportunistic yeasts, but live harmlessly.
• Can cause oral thrush, skin thrush, and vaginitis (candidiasis)
• Local infection develop into focal site for systemic infection

Subcutaneous & Systemic Mycoses

• Severe types of mycoses.
• Subcutaneous infections happen in of the dermis & underlying tissues.
• Arise from traumatic implantation into the subcutaneous tissue
• It look quite grotesque in appearance (e.g., Madura foot) and contain fungus bumps.
• Systemic are infections of internal organs (one, or multiple) at the same time
• Example, simultaneous respiratory and bloodstream infections.
• Conidia of pathogenic fungi come inhaled with dust from soil or dried bird or bat feces, or even through wounds of hands & feet
• When inhaled, they germinate and causes respiratory infection, similar to tuberculosis
• Examples include blastomycosis, coccidiodomycosis, cryptococcosis, and histoplasmosis.
• Can invade further and especially immunocompromised individuals
• Bread mould, such as, Rhizopus and Mucor spp., cause disease or death in immunocompromised, a condition called zygomycosis or mucormycosis.

Summary of Selected Fungal Diseases of Humans

• Yeasts
  • C. albicans causes thrush, yeast vaginitis, nail infections, and systemic infection
  • Cryptococcus neoformans causes cryptococcosis (lung infection, meningitis, etc.
• Moulds -Aspergillus spp. causes aspergillosis (lung infection, systemic infection) -Mucor and Rhizopus spp. as well bread mould varieties, causes mucormycosis or zygomycosis (lung infection, systemic infection) -Various dermatophytes causes tinea ("ringworm") infections
• Dimorphic fungi -Blastomyces dermatitidis causes blastomycosis (primarily a disease of the lungs and skin) -Coccidioides immitis and Coccidioides posadasii causes coccidioidomycosis (lung infection, systemic infection) -Histoplasma capsulatum causes histoplasmosis (lung infection, systemic infection) -Sporothrix schenckii causes sporotrichosis (a skin disease)
• Microsporidia -Nosema, Enterocytozoon causes eye infections and diarrhea
• Other -Pneumocystis jiroveci causes Pneumocystis pneumonia

Laboratory Diagnosis

• Clinical specimens are submitted to mycology section
• If and then when isolated, yeasts are identified through inoculated with to biochemical tests (rarely used).
• Substrates can be used to determine the type.
• Miniaturized biochemical test are commercially available
• Macro & microscopically and observed & the speed they grow

Lichens

• Mostly found in the woods
• Colored, circular patches on tree trunks & rocks
• The combination of algae with fungus
• Recent evidence includes yeast embedded in the cortex.
• Classified as Protists
• Relations are referred to as symbiotic relationships
• The relationship represents mutualism
• Not associated with human disease
• Have antibacterial properties

Slime Moulds

• Found in soil and on rotting logs
• Have fungal and protozoal characteristics
• Transferred to the Kingdom of Protozoa
• Not moulds
• Possess complex life cycles
• These start as an amoeba, progressing to multicellular organisms.
• Don't cause human disease