Viruses and Monerans What are viruses? –Very small particles made of nucleic acid and protein –contain either DNA or RNA but not both –nucleic acid is found inside a capsid

–capsid is a protein shell nucleic acid + capsid = nucleocapsid –some viruses have an envelope of lipid and protein surrounding nucleocapsid –host cell - cell in which a virus or an organism lives

Viruses are all intracellular parasites Parasites harm hosts + for parasite, - for host Parasite benefits, host is harmed

like a “building block” –capsomere - single protein subunit of a capsid; stacked together they form capsid

Ebola zaire

Classification of Viruses 1. Is it an RNA or DNA virus? 2. What is the shape of the capsid? 3. What is the size of the virus? –1 nanometer = 1 billionth of a meter –range from several nm to 300+ nm

4. Does the virus infect plants, animals, bacteria, or certain tissues in certain organisms? 5. Does the virus have an envelope? 6. How many capsomeres does it have?

Bacteriophages

Infect bacteria Experiments with phages could be done fairly quickly and provided a lot of information about viruses viral replication - takes place inside a host cell raw materials - amino acids and nucleotides (the units that make up a DNA molecule)

Tools - ribosomes and tRNA Energy - provided by ATP

Viral Replication Bacteriophage used as an example: 1. Sticks to host cell - by adsorption - molecules on viral tail closely fit host molecules 2. Injection of viral nucleic acid 3. Using host material, the viral nucleic acid makes copies of itself and the capsid

4. Assemble new viral particles 5. Lysis - the host cell bursts when many viral particles have been assembled - new particles infect other cells

–this entire process is the lytic cycle - each cycle can yield several hundred new phages –virulent phages - phages that cause lysis of host cell

Temperate phage - can stay inside host cells for a long time without causing lysis viral DNA incorporates itself into the host DNA prophage - viral DNA attached to bacterial chromosome –Bacteria + prophage = Lysogenic bacteria

Retroviruses RNA viruses Use RNA to make DNA (instead of using DNA to make RNA) they do it backwards - hence the name “retro” meaning backward HIV is a retrovirus responsible for certain types of cancers in animals and humans

Viral transduction Transfer of host DNA to another organism by a virus results from temperate phage becoming virulent they carry sections of the host DNA to other cells

Viroids infective strand of RNA lack capsid only replicate within a living cell infect plants

Prions Infective proteins cause Mad Cow Disease - Bovine Spongiform Encephalopathy cause Scrapie in sheep causes Kuru - similar to Mad Cow

Characteristics of Prokaryotes Kingdoms Archaebacteria and Eubacteria – old kingdom Monera Lack a nucleus and most organelles have cell membrane, cell wall, ribosomes,one main chromosome, may have DNA plasmid(s) some are autotrophs, some are heterotrophs

Kingdom: Archaebacteria Prokaryotes Ancient bacteria Live in extreme environments –ex: hyperthermophiles - very hot temperatures –methanogens - produce methane –halophiles - like it salty

Kingdom: Eubacteria Prokaryotes Bacteria that are found in most environments Include: –beneficial bacteria Decomposers (saprophytes) nitrogen-fixing bacteria bacteria used in food oxygen producing bacteria

AnabaenaBacillus subtilis

E. coli Clostridium botulinum

Shapes of bacteria Coccus (s)Cocci (pl) - spherical Bacillus (s) Bacilli(pl) - rod-shaped, capsule-shaped Spirillum (s) Spirilla (pl) - spiral, cork- screw

Other shapes –Coccobacilli – short rods –Square bacteria – from salty pools –Bacteria with extensions – prosthecae –Vibrio – gently curved rods –Pleomorphism- pleomorphic- variations in shape

Spirochetes - another group of spiral-shaped bacteria - one type causes syphilis

Size of bacteria coccus micron bacillus microns spirillum - several microns microns

Gleocapsa

Cyanobacteria - blue-green bacteria Autotrophic no nucleus, few organelles 2 pigments: – phycocyanin - blue –chlorophyll - green

May have other pigments - red, orange cell wall - provides support, made of amino acids and sugars binary fission - asexual reproduction; copy of DNA made and separated; cell pinches into two cells

important for food for aquatic organisms convert nitrogen gas to ammonia; some convert ammonia to nitrates release oxygen sewage promotes growth

Oscillatoria - high count reflects polluted water since sewage acts as a fertilizer promoting its growth

Bacteria Most are heterotrophic in every environment most bacteria are beneficial have a cell wall may have a capsule - outer layer which is usually made from sticky material so bacteria can stick to surfaces

2 special groups of bacteria 1. Mycoplasmas - smaller than most bacteria don’t have cell walls can cause lung infections

2. Rickettsias -.45 microns - bacteria-like –can’t live outside of host –can cause serious disease –ticks and lice are vectors –ex: Lyme disease, Rocky Mountain Spotted Fever

Nostoc Oscillatoria - high count reflects how polluted water since since sewage acts as a fertilizer promoting its growth

Oscillatoria

Bacterial arrangements Diplo - in pairs - ex: diplococcus Strepto - in chains - ex: streptococcus, streptobacilli Staphylo - in clusters - ex: staphylococcus

Large spirilla

Image: Yersinia pestis Fluorescence antibody positivity is seen as bright, intense green staining around the bacterial cell.

Yersinia pestis

The Black Death Necrosis (gangrene) of the tissue cause by pneumonic Plague

Bubo formed in groin Inflamed lymph nodes where the bacteria ultimately migrate