The Eukaryotic Members of the Microbial World

Chapter 12

Algae

Diverse group of eukaryotic organisms

Use light to convert carbon dioxide and water to carbohydrates

Includes both microscopic unicellular and macroscopic multicellular organisms

Algae

Classification of algae Algae not a distinct classification term Grouped for identification based on numerous

properties Photosynthetic pigments Cell wall structure Type of storage products Mechanism of motility Mode of replication

Names are derived from major color displayed by group

Algal habitats Found in both fresh and salt water and soil Aquatic algae major producers of oxygen

Also important users of carbon dioxide Algae often grow where other life forms can’t

Often first to become established in barren environments

Algae

Structure of algae Can be both micro and macroscopic Can float free or be propelled by flagella or

filaments Macroscopic algae are multicellular

Contain numerous structures for specific functions

Holdfast anchors organism to firm substrate Stapes hold blades which are the major

photosynthetic portion of algae Gas-containing bladders to help maintain blades in

proper position for maximum sunlight

Algae

Algae

Structure of algae Cell wall

Rigid structure made mostly of cellulose

Diatoms have silicon dioxide incorporated in cell wall

Cell structures Have membrane bound nucleus

containing DNA Have both chloroplast and

mitochondria Chloroplast for photosynthesis Mitochondria for respiration

Algae

Algae reproduction Most single cell algae

reproduce through binary fission

Chromosome goes through mitosis

Some algae reproduce through fragmentation

Portion of parent organism breaks off to form new organism

Sexual reproduction through meiosis also occurs

Algae Algae do not cause disease

directly Numerous algae produce toxin

Toxins are poisonous to humans

Some species such as dinoflagellates produce neurotoxins

Dinoflagellates eaten by shellfish and produce toxin

Toxin accumulates in shellfish tissues

Human eat shellfish and suffer paralytic shellfish poisoning

Protozoa

Microscopic unicellular organisms

Lack photosynthetic capability

Usually motile Reproduce by asexual

fission

Classification of protozoa Not a unified group

Lumped together as unicellular organism lacking chlorophyll

Traditionally divided into groups based on mode of locomotion

Some belong to phylum Sarcomastigophora Includes two subphyla

Mastigophora Sarcodina

Protozoa

Protozoa

Classification of protozoa Mastigophora

Includes flagellated protozoa Most significant include

Giardia lamblia, Leshmania species Trichomonas vaginalis and Trypanosoma species

Sarcodina Move by means of pseudopodia Entamoeba hystolytica produces disease in

humans

Classification of protozoa Other phylum include

Ciliophora Organism have cilia Balantidium coli only pathogenic ciliate

Apicomplexa Cause most serious protozoan disease

Plasmodium species causes malaria Microspora

Cause sever infection in immunocompromised

Protozoa

Protozoa

Protozoan habitats Majority are free-living

Found in marine, fresh water and terrestrial habitats Essential decomposers Require large amounts of moisture Important part of food chain

Protozoa eat bacteria and serve as food for larger species

Help maintain ecological balance in soil Important in sewage disposal

Results in decrease of sewage solids

Protozoa

Structure of protozoa Cell wall

Lack cell wall Shape determined by material beneath plasma

membrane Cell structures

Have membrane bound nucleus and organelles Lack photosynthetic chloroplasts

Have specialized structures for movement Cilia, flagella or pseudopodia

Protozoa grouped by mode of locomotion

Protozoa

Protozoan reproduction Life cycles complex

Often require more than one habitat or host

Polymorphic Can exist as trophozoite or as

cyst Both sexual and sexual

reproduction common Many replicate via binary fission Many replicate by schizogony

Many fissions Nucleus divides numerous times

then cell produces numerous single celled organisms

Fungi

Describes a taxonomic classification of organisms No longer includes slime molds and water molds

Fungi require organic compounds for energy and as a carbon source

Most are aerobic or facultative anaerobe Large number of fungi cause disease in plants

Only a few cause disease in humans

Classification of fungi Can be both micro and macroscopic Cell wall consist of chitin No flagellated cells Four groups of true fungi

Zygomycetes Basidiomycetes Ascomycetes Deuteroomycetes

A.k.a fungi imperfecta

Classification in groups based on sexual reproduction Except d where sexual reproduction is not seen

Fungi

Classification of fungi Zygomycetes

Includes common bread mold Rhizopus Ascomycetes

Includes the fungi of Dutch elm disease Basidiomycetes

Includes common mushroom and puffballs Deuteromycetes

Includes medically and commercially important species including the penicillium

Fungi

Fungi Classification of fungi

Grouping of fungal forms Yeasts

Single celled fungi Spherical, oval or cylindrical Reproduction through binary fission or budding

Molds Filamentous fungi contain hyphae collection of hyphae called mycelium Reproductive spore is single celled germinates to develop hyphae cells

divide into new form Dimorphic fungi

Can grow as yeast or mold depending on environment Many pathogenic fungi are dimorphic

Fungi

Fungal habitats Found in virtually every

habitat Mainly terrestrial

Fungal spores found throughout the earth

Uncountable numbers found in air

Major cause of asthma

Growth requirements of fungi Slightly moist environment

with high humidity 70% or higher

pH range varies Most grow well in

slightly acidic environment

Most are aerobic Some yeast facultative Some fungi obligate

anaerobes

Fungi

Fungal diseases in humans Cause disease in one of four ways

Allergic reaction Result from inhaling fungal spores

React to fungal toxin Many have hallucinogenic properties Certain species produces alflatoxin implicated in cancer

Mycoses Fungi grows on or in the body

Economic impact Destroy human food supply causing starvation

Fungi Symbiotic relationships of fungi

Form several symbiotic relationships with other organisms

Lichens result from relationship between fungi and photosynthetic organism

Relationships are very close Fungus provides protection and

growing platform Other organism supplies nutrient

Mycorrhizae symbiosis with roots of plants

Increases absorptive property of roots

Allow plant partners to grow in dryer climates

Fungi

Economic importance of fungi Many are important commercially

Saccharomyces used in production of beer, wine and bread

Many important for cheese production Penicillin, griseofulvin as well as other antimicrobials

are made from fungi Elimination of disease causing fungi from

commercial crops vitally important Fungi used in genetic and biochemical studies

Yeast genetically engineered to produce human insulin

Slime Molds and Water Molds

Used to be considered types of fungi They are completely unrelated Good example of convergent evolution

Two organisms develop similar characteristics and adaptations but not related on molecular level

Slime Molds and Water Molds Acellular slime molds

Terrestrial organisms Non motile Reproduction depends of formation of

dispersible spores Acellular slime molds readily visible in

environment Plasmodium formed from nucleus

spreads over surface of decaying matter

Cellular slime molds Has vegetative form made of ameba-

like cells Single cells congregate into form

called slug Slug forms fruiting body and spores

Slime Molds and Water Molds

Water molds A.k.a Oomycetes Members of heterokonts Do not have chlorophyll Once considered fungi

Due to morphology Form masses of white thread on decaying

matter Zoospores cause serious disease of food

crops

Multicellular Parasites:Arthropods and Helminths

Arthropods include Insects such as

mosquitoes responsible for transmission of malaria and fleas which transmits plague

Ticks responsible for transmission of Rocky Mountain Spotted Fever and Lyme disease

Lice responsible for transmission of typhus and other fevers

Mites transmit scabies

Helminths include nematodes, cestodes and tremetodes Cause disease by

invading host tissues and robbing nutrients

Nematodes invade gastrointestinal tract and blood stream

Cestodes associated with meats especially pork

Transmission results from consumption of uncooked meat

Trematodes Can be found discharged

in waters such as lakes and ponds