Microbes Bacteria Viruses Protists and Fungi Prokaryotes Prokaryote

Microbes – Bacteria, Viruses, Protists and Fungi

Prokaryotes • Prokaryote – unicellular organism without a nucleus – DNA is found in the cytoplasm

Classifying Prokaryotes • 2 Kingdoms of Prokaryotes – Eubacteria • Have peptidoglycan in cell walls • Includes most of the bacteria – Archaebacteria • Live in unusually harsh environments such as hot springs, stomach acid, and salty water. • No peptidoglycan in cell walls • Cell membranes and r. RNA different than Eubacteria

Identifying Prokaryotes • Prokaryotes can be identified based on the following: 1. Shapes 2. Cell Walls 3. Movement

Shapes • 3 Shapes 1. Bacilli – rod shaped 2. Cocci – spherical shaped 3. Spirochetes – spiral & corkscrew shaped

Cell Walls • Eubacteria can be separated based on Gram staining. – Gram Positive • Eubacteria cell walls have a thick layer of peptidoglycan that absorbs only violet dye and appears purple. – Gram Negative • Have an extra layer of lipid on the cell wall that stops the purple stain from entering and appears pink

Movement • Stationary – Some bacteria do not move. • Flagella (tails) – Whip like structures used for movement. • Other – Spiral shaped bacteria move in a corkscrew Motion – Myxobacteria produce a layer of slime to glide in.

Obtaining Energy • Autotrophs (Make their own energy) – Photoautotroph – uses the sun – Chemoautotroph – oxidize inorganic compounds as food. • Heterotrophs (Rely on other organisms for energy) – Fermentation – ferment sugars – Saprophytes – feed on dead things • Photoheterotrophs (A mix between the two) – are both autotrophic and heterotrophic – Use energy from the sun, but they require organic substances such as alcohol, fatty acids or carbohydrates.

Growth and Reproduction • Bacteria divide very quickly, as often as once every 20 minutes! • Binary Fission – Asexual reproduction where the bacteria divide into identical cells.

Endospore • Endospore – a structure produced in unfavorable conditions - A thick internal wall encloses the DNA and cytoplasm

Gene Transfer (Bacterial Evolution) • Mutation – random changes in DNA -passed on to daughter cells -one of the main way prokaryotes evolve • Conjugation – Bacteria make a bridge and exchange genetic material. • Transformation – Bacteria incorporate DNA from dead bacteria. • Transduction – Use viruses to transfer DNA from bacteria to other bacteria.

Importance of Bacteria • Decomposers • Producers • Nitrogen Fixers

Decomposers • Decomposers – Bacteria that break down complex molecules of dead organisms (trees, corpses) into simple molecules such as water, nitrogen compounds, and CO 2

Producers • Producers – food chains are dependent on bacteria for producing food – 1 cyanobacterium (Prochlorococcus) is the most abundant photosynthetic organism – makes over ½ of food in the open ocean

Nitrogen Fixers • Nitrogen Fixers – converts nitrogen into a form plants use (N 2 to NH 3) – 90% of the nitrogen organisms use comes from fixation – Fix nitrogen to ammonia. – Ex: Rhizobium grows in nodules of the roots of soybeans and other legumes. It is a mutual relationship where the plant provides nutrients for bacteria and the bacteria converts nitrogen for the plant.

Bacteria and Disease • Pathogens – • Disease causing agents. 2 Ways Bacteria cause Disease 1. Damage Tissues – damage tissues of the infected organisms directly by breaking them down for food. – Ex: Tuberculosis – bacteria break down lung tissue. 2. Toxins – release toxins that harm the organism. – Ex: Streptococcus: causes strep throat, if untreated, the bacteria releases toxins causing a rash known as scarlett fever.

Bacterial Diseases

Human Uses of Bacteria • Food – Bacteria are used to make cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut and vinegar. • Drugs (Medicines) – Also used to synthesize drugs such as insulin. • Environmental Use – Certain bacteria are used to digest petroleum after an oil spill.

Controlling Bacteria • Physical Removal – hand washing removes bacteria • Disinfectants - chemicals that kill bacteria • Food Storage – - refrigeration/freezing slows the growth • Food Procession – boiling, frying, steaming kills bacteria • Sterilization by Heat – kills bacteria

Controlling Bacteria (Cont. ) • Vaccines – a preparation of weakened or killed pathogen or inactivated toxin - The vaccine stimulates the body to produce immunity to a specific disease • Antibiotics – block the growth and reproduction of bacteria - Disrupt proteins or cell processes specific to bacterial cells - Do not harm host’s cells

Superbugs • Use of antibiotics has lead to bacteria that are resistant to antibiotics – Penicillin killed many infections in the 1940 s when it was introduced. Now is has lost effectiveness – Bacteria that are resistant to penicillin reproduce and pass resistance on through conjugation – MRSA – skin infection spread by close contact

Viruses

Viruses • Virus – Latin word for poison – Viruses are particles of nucleic acid, protein and sometimes lipids – Not alive because they are not able to reproduce independently – Reproduce by entering living cells and use the infected cell to produce more viruses

Structure of Viruses • Core – A core of either DNA or RNA • Capsid – A protein coat that surrounds the core – Has proteins that enable the virus to enter cells

Viral Infections • Viral Infection – Occur when viruses bind to specific proteins on the cell surface. Most viruses are very specific to the cells they infect. • Bacteriophages – viruses that infect bacteria

Lytic Cycle • • Virus enters the cell Virus destroys host DNA Uses the host cell to make copies of itself Host cell lyses (bursts) soon after infection releasing virus particles

Lysogenic Cycle • Virus imbeds its DNA into the DNA of the host cell and is replicated along with the host cell’s DNA. The cell doesn’t lyse right away. • Prophage –The viral DNA that is embedded in the host’s DNA

Viruses and Disease • Adenoviruses – Naked viruses w/linear DNA – Polio, measles, mumps, yellow fever, colds, and flu • Oncogenic Viruses – Disrupt normal controls on cell growth causing cancer. • Retroviruses – Usually RNA is copied from DNA, but in retroviruses DNA is copied from the viral RNA (Ex: AIDS)

RNA Viruses • 70% of viruses have RNA instead of DNA • RNA viruses cause colds, AIDS, cancer and others

The common cold • The virus is brought in the host cell (nose, etc. ) • The host cell makes viral protein and RNA • Within 8 hours the hose cell bursts and releases hundreds of new viruses

HIV • HIV is a retrovirus – the genetic information is copied from the RNA to DNA • The viral DNA remains inactive for many cell divisions • When activated, the viruses damage the host’s immune system.

VIRUSES vs. CELLS • Viruses have many characteristics of cells • Viruses depend on living things and therefore were not likely to be the first living organisms.

New Viruses • Genetic makeup of viruses changes quickly and allows a virus to jump form one species to another. - AIDS may have jumped from nonhuman primates - “Bird flu” is a concern because it may jump to humans and is similar to some of the most deadly human versions of the flu

Prions • Prions – particles that contain no DNA or RNA, only proteins. – Misfolded proteins that cause other proteins to misfold. • Examples – Mad Cow Disease – Scrapies – TSE (Transgenic Spongiform Encephalitis) • The human form of mad cow. Proteins that come into contact with the prion unwind making holes in the brain so that it looks like a sponge. • How Prion's Kill

Protista

Protists • Eukaryotes that don’t fit into the plant, animal or fungi kingdoms. • Most are unicellular but can be multicellular

Movement • Pseudopods • Cilia • Flagella

Reproduction • • Asexually by mitosis Sporangium Conjugation Sexual Reproduction – Alternation of generations

Examples of Protists • Amoeba • Paramecium • Euglena

Ecological Significance • Parasites/Disease Causing Protists – Causes harm to host organism – Ex: Malaria • Mutualists – Lives within an organism – Both organisms benefit – Ex: Termites

Fungi

Fungi • Fungi – Heterotrophic • Feeds on other organisms – Eukaryotic – Cell Walls with Chitin

Structure of Fungi • • • Fruiting Body – Main structure of the Fungi – Reproductive structure Mycelium – Mass of branching hyphae below the soil Hyphae – Cells that are long, slender branching filaments – Make up both the fruiting body and the mycelium

Life Cycle • Spores – Asexual form of reproduction, the spores travel through air/water • Sexual Reproduction

Significance of Fungi • Parasites – Ex: Ringworm • Lichens – Partnership of fungi and algae • Mycorrhizae – Help feed plants