Bacteria constitute a large domain of prokaryotic microorganisms.

Viruses and Prokaryotes What is a Virus? • A virus is a noncellular particle made up of genetic material and protein that can invade living cells • Structure – Core of nucleic acid surrounded by a protein coat called a capsid – Capsid can be DNA or RNA, but not both – Core can be several to several hundred genes SO HOW BIG ARE VIRUSES??? • Viruses are REALLY small. • They are much smaller than bacteria. • They can only be seen with an electron microscope. Bacteriophage • Bacteriophages are viruses that infect bacteria • Bacteriophage – Head – capsid and DNA – Tail – with fibers to attach to bacteria T group • Most commonly studied are T group – T1, T2, T3, T4 etc • T4 has a DNA core within a protein coat, and tail with tail fibers to attach to bacteria. Viral shapes • Variety of shapes – Rod – Tadpole – Many sided, helical or cubelike VIRUS SHAPES • Round • Rod-shaped • Many sided (icosohedral) SHAPES MAY DIFFER BUT… T4 Bacteriophage Tobacco Mosaic Virus Influenza Virus Head Tail sheath DNA Tail fiber RNA Capsid Surface proteins Membrane envelope RNA Capsid proteins • All viruses have • 1. Chromosome-like part that carries hereditary information – The Core • 2. Protein coat: Protects hereditary information and provides the shape! The Capsid ROUND VIRUSES • Herpes virus – There are two types: • Genital • oral ROD-SHAPED • Tobacco mosaic virus [...]... copies of their RNA genes • Retroviruses have their genetic information copied backwards RNA  DNA • One retrovirus is HIV Others cause cancer in animals and humans • The theory is that viruses were not the first living things They are dependent on living things to survive EUBACTERIA AND ARCHAEBACTERIA: The two bacterial kingdoms Bacteria on a pin head Eubacteria • “True” bacteria • largest Kindgom of. .. – 2 kingdoms – Eubacteria and archaebacteria Archaebacteria • Archaebacteria includes organisms that live in very harsh environments • Methanogens – live in oxygen free environments – mud, digestive tracts of animals • Extremely salty environments • Hot springs Identifying Bacteria • Cell Shape – Rod – bacilli – Sphere – cocci – Spiral – spirilla Bacterial Shapes Round Rod Spiral Arrangement • 2 cocci... complete virus particle does not enter 2 Growth – Bacterium can’t tell difference between bacterial and viral DNA RNA polymerase causes mRNA to be made from cell for virus Viral DNA takes over and produces more DNA and viral proteins 3 Replication – Virus uses bacterial material to make thousands of copies of the protein coat and DNA Cell becomes filled with virus particles (All three stages can happen with... them to break down cellulose (in grass and hay) Bacteria in the Environment • Bacteria are like the stage hands that allow the show to go on without being seen (or always given the credit) • Bacteria recycle and decompose dead material • Saprophytes – organisms that use the complex molecules of a once living organism as their food source Sewage decomposition • Sewage treatment – bacteria is added directly... Some plants have a symbiotic relationship with nitrogen fixing bacteria • soybean – Rhizobium grows in nodules around roots Diseases caused by Viruses and Monerans • only a small number of viruses and bacteria can cause disease • Pathogens – organisms that cause disease • All viruses infect living cells • Disease occurs when infection causes damage to the cells Viruses and Disease • Examples are: –... of lipid and carbohydrate – picked up safranine – appeared red GRAM NEGATIVE Bacterial movement • propelled by flagella • lash, snake, or spiral forward • no movement Bacterial Respiration • Obligate aerobes – require oxygen • Obligate anaerobes – must live in absence of oxygen – example is Clostridium botulinum • Facultative anaerobes – can live with or without oxygen Reproduction • Some can reproduce... DNA serves as central point for virus particles to be assembled Cells fill with virus and lyse (burst) New viruses can now infect new cells SO HOW DO VIRUSES CAUSE DISEASE? Section 19-3 Bacteriophage protein coat Bacteriophage DNA Bacterial chromosome Bacteriophage attaches to bacterium’s cell wall Bacteriophage enzyme lyses the bacterium’s cell wall, releasing new bacteriophage particles that can attack... attack other cells Lytic Cycle Bacteriophage injects DNA into bacterium Bacteriophage proteins and nucleic acids assemble into complete bacteriophage particles Bacteriophage takes over bacterium’s metabolism, causing synthesis of new bacteriophage proteins and nucleic acids Bacteriophage Bacteriophage DNA Bacteriophage protein Retroviruses • RNA viruses • When they infect a cell, they produce DNA copies... the raw sewage • How does a septic tank work? Nitrogen Fixation • All organisms are TOTALLY dependent on monerans for Nitrogen • All Plants need nitrogen to make amino acids (NH2) • Because animals eat plants, they get their proteins from plants • What percentage of the air is Nitrogen? • Plants, and most other organisms cannot use this directly • Need Nitrogen to be “FIXED” chemically as ammonia Nitrogen... Nitrogen Fixation • Scientists can make synthetic nitrogen containing fertilizers by mixing Nitrogen and Hydrogen gases, heating to 500 degrees C and compressing it to 300 X normal atmospheric pressure – dangerous, expensive, time consuming • Many cyanobacteria can take nitrogen from the air and convert it to a useable form – this is called Nitrogen Fixation • Bacteria are the only organisms that can do