Ch 19- Bacteria and Viruses• http://player.discoveryeducation.com/index.cfm?guidAssetId=9A7AFEE4

-3E11-4820-8597-5403F1802ADA&blnFromSearch=1&productcode=US• Prokaryote- unicellular organisms that lacks a nucleus• How do the two groups of prokayotes differ?

– Make up of cell walls– Archaebacteria lack peptidoglycan, have different membrane lipids– DNA sequence is more like eukaryotes than eubacteria– Thought to be ancestors of eukaryotes– Eubacteria live almost everywhere and archaebacteria live in extremely harsh

environments• What factors are used to identify prokaryotes?

– Shape– Chemical nature of their cell walls– Movement– How they obtain energy

Identifying Prokaryotes

• Shapes– Bacilli are rod shaped– Cocci are spherical shaped– Spirilla are spiral and corkscrew shaped

• Cell walls- gram staining to tell apart– Gram positive- thick peptidoglycan walls, appear violet– Gram negative- thinner walls, appear pink or light red

• Movement- some move and some don’t– Flagella- whiplike structures used for movement

Metabolic Diversity

• Heterotrophs- consume organic molecules made by other organisms– Chemoheterotrophs- take in organic molecules– Photoheterotrophs- photosynthetic and take in

organic compounds for carbon source• Autotrophs- produce own food– Photoautotrophs– Chemoautotrophs- do not require light, use

energy from chemical reactions

Growth and Reproduction

• Binary fission- form of asexual reproduction where cell doubles in size, replicates DNA and divides in half, produces two identical daughter cells

• Conjugation- the exchanging of genetic information between bacteria

• Endospore- forms when growth conditions become unfavorable– Bacterium produces thick internal wall, encloses DNA,

remains dormant for months or years

Importance of Bacteria

• What is the importance of bacteria?– Vital to maintaining living world– Producers and decomposers

• Decomposers recycle nutrients• Nitrogen fixation- converting nitrogen gas into form plants

can use• Used in foods and beverages• E. coli break down food in intestines• Bacteria in extreme environments- rich source of heat

stable enzymes– Medicine, food production, industrial chemistry

Sec 2- Viruses

• What is a virus?– Composed of core of DNA or RNA surrounded by protein

coat– Reproduce only by infecting living cells– Enter living cells, use infected cell to produce more viruses– Vary greatly in size and structure

• Welcome to Discovery Education Player• Capsid- virus’s protein coat• Most are highly specific to cells they infect• Bacteriophages- viruses that infect bacteria

Viral Infection

• Lytic infection- virus enters a cell, makes copies of itself, and causes the cell to burst– Injects host cell with viral DNA, mRNA is made by the host

cell from viral DNA into viral particles• Lysogenic infection- virus integrates its DNA into the

DNA of the host cell– Viral genetic information replicates along with host cell’s

DNA– Does not lyse the host cell right away– Prophage- viral DNA that is embedded in the host’s DNA– May stay for many generations

Retroviruses

• Viruses that contain RNA as their genetic information

• Produce a DNA copy of their RNA, inserted into DNA of host cell

• May remain dormant for lengths of time, directing production of new viruses-cause death of new cell

• Responsible for some types of cancer • Acquired immune deficiency syndrome (AIDS)

Are viruses alive?

• Reproduction– Only within host cell

• Regulate gene expression• Genetic code

– DNA or RNA• Evolve• Do not………

– Grow or develop – Obtain and use energy– Respond to environment

• Viruses are completely dependent upon living things

Sec 3- Diseases Caused by Bacteria and Viruses

• Pathogens- disease-causing agents• How do bacteria cause disease?

– Damage the cells and tissues of infected organism directly by breaking down the cells for food

– Release toxins or poisons that travel throughout the body interfering with the normal activity of the host

• Mycobacterium tuberculosis- causes tuberculosis, destroys lung tissue

• Streptococcus- causes strep throat, releases toxins in bloodstream and can cause scarlet fever

• Corynebacterium diphtheriae- causes diphtheria, releases toxins into bloodstream that destroy tissue, can lead to trouble breathing, heart failure

How to prevent disease?

• Vaccine- preparation of weakened or killed pathogens– Prompts body to produce immunity to disease– Immunity- body’s ability to destroy new pathogens

• Antibiotics- compounds that block the growth and reproduction of bacteria– Penicillin

• How can bacterial growth be controlled?– Sterilization, disinfectants, and food processing

• How do viruses cause disease?– Produce disease by disrupting the body’s normal

equilibrium• Many attack and destroy certain cells in body– Cause symptoms of disease– Poliovirus

• Other cause cells to change patterns of growth and development

• Cannot be treated with antibiotics

• Viruses in animals– Foot-and-mouth disease infected cattle, sheep, and pigs in

Europe in late 90’s• Viruses in plants– Tobacco mosaic virus– Difficult with cell walls

• Viroids- single stranded RNA molecules that have no surrounding capsids

• Prions- protein infectious particles, contain no DNA or RNA– May be cause of mad cow disease