Students will begin to explore the differences between viruses,

bacteria, and fungi

The Diversity of LifeThe Diversity of Life

Today…

• VirusesThe six kingdoms (Living Things)• Prokaryotes

– Archaebacteria– Eubacteria or Bacteria

• Eukaryotes– Animalia– Plantae– Protista– Fungi

VIRUSES• Viruses are non-living particle.• Technically they are not considered living

organisms, since they cannot self replicate (they’re not a kingdom)

• Remember that living organisms: MRS GED1. Made of cells2. Able to self reproduce (sexually or asexually)3. Respond to stimuli4. Grow & develop5. Take energy & use it 6. Stable chemical composition (DNA and other

chemicals)

Virus structure• Viruses: Just a protein coat

for protection (capsid) and a nucleic acid (RNA or DNA) for information on how to make more copies of the same virus

• Cannot replicate/reproduce onits own! Needs a host…

Virus is a cellular parasite

• Uses cell machinery of a host cell to replicate and to produce more viruses

• They come in many varieties, sizes & shapes.

Refer to Virus handout describing replication also known as the lytic cycle

Viruses cause diseases• Viruses cause numerous diseases in Plants, animals,

bacteria & fungi…• Examples of human viruses:

– Herpes virus– Hepatitis virus– Rabies– Influenza (“flu”) – respiratory infection (fever, headache, chills,

cough, stuffy nose, sore throat) caused by a variety of viruses. Flu season: Nov. – March.

* May be Passed on by sneezing, coughing – air, hand-to-mouth, etc.

* Vaccine helps prevent outbreaks.

Plant Viruses• Tobacco Mosaic Virus (TMV) causes

mottling symptoms• Rose mosaic virus• Spots on fruit• Wheat stunt virus

Living organisms• PROKARYOTIC – Lack membrane-bound

organelles; no nucleus present– Kingdom Archaebacteria and Eubacteria

• EUKARYOTIC – have membrane bound organelles with a nucleus.– Kingdoms Protista, Plantae, Fungi, Animalia

PROKARYOTES• Bacteria are small and unicellular• They have no internal

organelles (no chloroplasts, nucleus, ER, mitochondria, etc.)

• Bacteria have a cell walllike plant cells.

• Bacteria have ribosomes.

Bacteria• Replication is asexual – clonal, rapid simple

division (no mitosis); reproduce by binary fission

• Pseudo-sexual reproduction, has means for Genetic exchange

• Called conjugation

Bacteria• Bacterial forms: cocci (round), bacilli (rod),

spirilli (spiral)

• Some forms are photosynthetic: cyanobacteriachloroplasts are present

Bacterial pathogens in Animals

• Typhoid, tuberculosis• Bubonic plague or “Black Death”,

transmitted by fleas (caused 25 million deaths in Medieval Europe)

• E. coli, Salmonella (food poisoning)76 million illnesses worldwide

Bacterial control• There are ways of controlling bacterial

growth: • Disinfectants • Antibiotics • Low temperatures• High temperatures, • Low oxygen

Beneficial Bacteria

• Decomposition in the biosphere – get rid of dead organisms, nature’s recyclers

• Intestinal Bacteria – supply vitamins (K)

• Commercial use: yogurt, sour cream, fermentation• Genetically-engineered bacteria produce insulin

and other important chemicals.• Can also help clean up oil spills: oil ‘eating’

bacteria!

Eukaryotes• Four Kingdoms:

Fungi, Protista, Plantae, Animalia

• Have organelles (nucleus, mitochondria, etc.)

Kingdom Fungi

• Characteristics of fungi:• Eukaryotic• Non-photosynthetic, must obtain nutrients by

absorption (produce digestive enzymes)• Have a cell wall! Fungi cell wall is made of

chitin and/or cellulose

Fungal morphology

• Most fungi come in thread-like strands, called hyphae (collectively called mycelium)

• Other fungi are single-celled, called yeasts.• Form spores that can spread by wind, air or soil (give

us allergies!)• Fungi are so successful because they can reproduce

both sexually and asexually– Sexual spores – (by meiosis) mushroom is spore-producing

structure, formed by many hyphae– Asexual spores (by mitosis)

Fungi Hyphae: filaments

Significance of Fungi

• Many fungi are beneficial

• As decomposers: fungi obtain nutrition from organic matter, so they recycle nutrients

Fungi act as antibiotics• Penicillin is produced by species of the fungus

Penicillium, which kills bacteria.• Discovered by Alexander Fleming in 1928.• Left some unwashed plates with bacteria, went

on vacation, and saw that a mold was growing, inhibiting the growth of the bacterial colony (Nobel Prize 1945).

Pathogenic fungi• Pathogenic fungi grow within a host, using the

host as food for replication• Human Diseases:

• Athlete’s foot• Yeast infections• Ring worm

• Candidiasis

Pathogenic fungi: Mycotoxins• Mycotoxins are harmful, toxic chemicals

produced by fungi and which accumulate in infected food

• Aflatoxins contaminate corn and peanuts.• The Aspergillus fungi grows on corn/peanuts

and makes one of the most potent carcinogens known (aflatoxins)

Commercial uses of fungi

• Bread making – carbon dioxide bubbles help dough rise

Commercial uses of fungi• Edible fungi are the sexual structures of

fungi, the mycelium remains • Mushrooms• Morels• Truffles

Other types of fungus• Poisonous – some very dangerous

intoxicants

• Hallucinogenic fungi