Viruses Bacteria Protists Fungi 1 Viruses viroids prions

Viruses, Bacteria, Protists, Fungi 1. Viruses, viroids, prions

Virus name means poison term was used to describe pathogens in the late 1800 s viruses are noncellular infectious agents (nonliving)

A virus contains two parts: protein coat-protects genetic material nucleic acid (either DNA or RNA but not both)

Some examples: Ebola

Common cold

Polio

Rabies

Herpes

Measles

A virus cannot reproduce itself-it must enter a cell and take over In a series of steps, like an assembly line, a host cell makes virus parts and puts them together.

Viruses are host specific: Bacteriophages-attack only bacteria (because bacteria reproduce quickly these viruses are often used to study viruses. ) Animal viruses Plant viruses (have to be able to breach the cell wall--often they hitch a ride on a piercing insect)

Other infectious agents: Prions-small proteins or altered products of a gene (mad cow, scrapie)

Viroids-tightly folded strands or circles of RNA, no protein coat, cause plant diseases, resemble introns Potato plant viroid

Viral replication 1. Attachment-virus attaches to host cell- recognized chemically 2. Penetration-nucleic acid enters cell 3. Replication and synthesis-host cell is directed to make virus parts 4. Assembly-viral nucleic acid and protein are put together 5. Release-cell bursts and releases viruses

Lytic cycle-above steps proceed rapidly after infection. Symptoms felt within a short time period. Lysogenic cycle-virus enters a latent period, infection is delayed. Virus becomes part of cell DNA and is passed to other cells in mitosis. Eventually something triggers it to start lytic cycle.

Viruses with RNA Called retroviruses-enter a cell but first must make DNA before it can be replicated. (RNA serves as a template to form DNA)

Bacteria The most abundant organisms found everywhere (hot springs, volcanoes, snow) prokaryotic, circular DNA usually have a cell wall reproduce by fission

A bacterial cell

Bacteria shapes coccus-round bacillus-rod spirillum-spiral

Growth patterns strep-chains staph-clumps or clusters diplo-in pairs tetra-fours

Shape and Pattern together Streptococcus Staphylococcus

Bacteria size Bacteria are the smallest of all cells. They range from 1 to 10 micrometers http: //www. cellsalive. com/howbig. htm

Staining-for identification of the cell wall. Gram stain-process of staining that involves several steps and 2 dyes. Identifies the bacteria by cell wall type. ◦ purple is crystal violet-gram positive (cell wall is one thick layer) ◦ red is safranine-gram negative (cell wall is 2 thin layers)

Gram negative rods Gram positive cocci

Classification: Originally classification was by shape, size, motility, staining, metabolism. Now biochemistry is used-proteins and RNA are compared. This changes how bacteria were classified.

Types of bacteria Eubacteria-most common Archaebacteria-have different genes, ribosomes and lipids. Match to a common ancestor with eukaryotic cells

Bacterial growth and reproduction growth is measured not in size of cell but in increase in the number of cells in ideal conditions many bacteria can divide as fast as every 30 minutes (a few even as fast as 10) fortunately, conditions are rarely ideal!

Fission 1. Parent cell replicates its DNA. Both are attached to the cell membrane.

2. Membrane grows so cell stretches and pulls two DNA apart.

3. New cell wall material is deposited above the membrane and grows through the midsection. 4. Results in 2 identical cells

Conjugation Bacteria also contain plasmids-small circular DNA. ◦ a sex pilus forms-donor cell hooks onto recipient cell and pulls it close ◦ conjugation tube forms between them ◦ plasmid DNA is transferred through the tube ◦ replication of plasmid occurs in both ◦ cells separate

Infectious diseases infection-pathogen invades body, multiplies in cells and tissues disease-result on the body of an infection contagious-pathogen can be transmitted from person to person

epidemic-spreads rapidly for a limited time pandemic-spreads in several places endemic-prevalent in a particular area

Tetanus

Tuberculosis

Staph skin infections

MRSA-methicillin resistant staphylococcus aureus

Whooping cough

Bubonic plague

Protists all are eukaryotic classified by what they are not may be photosynthetic some are multicellular

Fungus like Protists Water molds Slime molds- ◦ cellular ◦ plasmodial

Animal like Protists Sarcodina-some make shells, move by pseudopods ◦ examples-ameba, radiolarians

flagellates ◦ example-giardia sporozoans-parasitic ◦ example-plasmodium

Mosquito bites human, injecting saliva that contains Plasmodium sporozoites Anopheles mosquito bites infected human and picks up Plasmodium cells Infected red blood cells burst, releasing Plasmodium cells; some can infect other red blood cells, and others can infect mosquitoes Liver Infected liver cells burst, releasing Plasmodium cells that infect red blood cells Red blood cells

Ciliophora-ciliates ◦ example-paramecium

Plant like Protists Euglenaphyta-both heterotrophic and autotrophic

Chrysophyta-golden algae-diatoms (shells)

Pyrrhophyta-marine, dinoflagellates, some make toxins (red tide)

Rhodophyta-red algae, marine, important in coral reefs and making agar

Phaeophyta-brown algae ◦ common seaweeds like kelp, used to smooth and thicken various products ◦ also important as a habitat for animals Chlorophyta-green algae, mostly freshwater

Fungi Kingdom decomposers heterotrophic extracellular digestion (secrete enzymes)

Main Structures: spores-reproductive cells mycelium-mass of branched threads hyphae-individual threads

Types of fungi (classified by their method of reproduction) 1. Club (Basidiomycota)-hyphae form a club-like structure ◦ mushrooms, puffballs, rusts, smuts 2. Sac fungi (Ascomycota)-hyphae form a sac-like structure ◦ yeast, truffles, morels, penicillin, aspergillis

Truffles

Yeast

Puffballs

Mushrooms

Bracket fungi

Death cap-most poisonous mushroom

Morels

3. Common molds (Zygomycota)--forms a zygospore with thick walls ◦ black bread mold, dung fungus

4. Imperfect fungi-(Deuteromycota) no known form of sexual reproduction ◦ Examples-athlete’s foot and ringworm

Importance of Fungi 1. Symbiotic relationships a. lichens-a fungus and a plant (algae)pioneer organisms, turn rock into soil, indicator of pollution. Algae makes food, fungus provides a home

b. mycorrhizae-fungus and tree roots-tree gets minerals from fungus, fungus gets carbohydrates from tree

2. Foods-flavors in some cheeses, edible fungi, soy sauce, bread, alcohol 3. Medicines-antibiotics

4. Crop destruction (loss is in the millions of dollars) 5. Decomposers-recycling of organic material