The virus

“For about 100 years, the scientific community has repeatedly changed its collective mind over what viruses are. First seen as poisons, then as life-forms, then biological chemicals, viruses today are thought of as being in a gray area between living and nonliving: they cannot replicate on their own but can do so in truly living cells and can also affect the behavior of their hosts profoundly. The categorization of viruses as nonliving during much of the modern era of biological science has had an unintended consequence: it has led most researchers to ignore viruses in the study of evolution. Finally, however, scientists are beginning to appreciate viruses as fundamental players in the history of life.”

What is a virus??? Particles of nucleic acid, proteins, and in some cases, lipids Reproduce only by infecting other cells Vary widely in size and structure

BACTERIOPHAGE

The Common Cold Virus

HIV

Virus “life” cycle

retroviruses

All viruses enter living cells and, once inside, use the machinery of the infecte cell to produce more viruses

How a Virus Invades Your Body

BACTERIA

microscopic life that covers nearly every square centimeter of the Earth yet was completely unknown until the invention of the microscope “

What are bacteria??? Prokaryotic cells- which means what exactly? Smallest and most common microorganism Range in size from 1 to 5 micrometers (unless you are a Epulopiscium fisheloni in which case you are much larger) Often thought of as bad guys but really not so much

Classification of bacteria

Eubacteria Largest group, quite varied Find living almost everywhere Cell wall made of a carbohydrate called “Peptidoglycan” The cell wall: 1. protects from injury 2. determines shape of bacteria

ARCHAEBACTERIA Cell wall lacks peptidoglycans DNA sequences more similar to that of Eukaryotes suggesting they may be the early ancestors of eukaryotic organisms Able to live in very harsh environments such as salt water and hot springs. Methanogens live in oxygen-free environments such as thick mud and intestines of animals methane gas

We can identify bacteria by their : 1.Shape a. Cocci b. Bacilli c. Spirilli

GRAM + GRAM - 2. Nature of Cell Wall GRAM + (with peptidoglycan) GRAM - (without peptidoglycan)

3. Movement- if and how flagella or slime Flagellar Motion

Bacteria can be heterotophic or autotrophic when they eat. Bacteria can be aerobic and carry out respiration, anaerobic causing fermentation or a Bit of both- facultative

Bacteria make more bacteria through: Binary FissionConjugation b.f. Spore Formation

Significance of bacteria 1.Capture energy through photosynthesis 2.Decomposers 3.Nitrogen-fixers 4.Produce food and beverages 5.“Eat” small oil spills 6.Purify H2O 7.Synthesize drugs, chemicals 8.Produce vitamins in human gut

And sometimes they make us sick… Pathogens

120,000 to 150,000 different species of bacteria are thought to exist. But less than 1% of these make us sick

Antibiotic resistance