Chapter 19 Bacteria and Viruses

I. Prokaryotes A.Prokaryotes: single-celled organisms that lack a nucleus 1. Eubacteria – walls contain peptidoglycan (a carbohydrate) 2. Archaebacteria – lack peptidoglycan, DNA similar to eukaryotes

B.Identifying Prokaryotes 1. Shapes a. Bacilli (rod shaped) a. Bacilli (rod shaped) b. Cocci (spherical) b. Cocci (spherical) c. Spirilla (spiral) c. Spirilla (spiral)

2. Cell Walls a. Gram-positive (with peptidoglycan) – purple b. Gram-negative (without peptidoglycan) – red

Which bacteria is rod shaped and has peptidoglycan in its cell walls? This one?NO…it has spheres! This one?NO…it has spheres! This one?NO….why? This one?Yes!

3. Arrangement a.Staphyl: Clumps or clusters b. Strepto: long chains

4. Movement a.Propelled by tail-like structure called flagella b. Glide along a slime secretion c. Move along like snakes d. Some do not move

C.Obtaining Energy 1. Autotrophs a. Photoautotrophs: obtain energy from photosynthesis a. Photoautotrophs: obtain energy from photosynthesis b. Chemoautotrophs: obtain energy from inorganic molecules b. Chemoautotrophs: obtain energy from inorganic molecules

2. Heterotrophs a. Can cause food poisoning b. Photoheterotrophs: photosynthetic, but also need organic compounds for nutrition

D.Releasing Energy 1. Obligate aerobes: require oxygen 2. Obligate anaerobes: cannot live in presence of oxygen 3. Facultative anaerobes: do not need oxygen, but can live in the presence of it

E.Growth and Reproduction 1. Binary fission: cell divides, asexual 2. Conjugation: transfer of genetic information from one cell to another, sexual 3. In unfavorable conditions, many bacteria can form endospores – can remain dormant for months or years

II. Bacteria in Nature A.Decomposers 1. Help recycle nutrients – break down dead organisms 2. Used in sewage treatment

B.Nitrogen Fixers 1. Nitrogen fixation: converting nitrogen into a form plants can use 2. Rhizobium grow on roots of soybeans and other legumes – converts nitrogen to ammonia for the plant

Nitrogen-fixing bacteria Rhizobium on the roots of the broad bean plant Vicia faba. The roots of the host plant become infected with the bacteria as seedlings, and respond by surrounding the bacteria with root hairs. The relationship between a particular host species and a particular bacterium is highly specific, and is regulated by a series of recognition events that prevent the wrong species of bacterium from taking up residence in the wrong plant.

C.Bacteria and Disease 1. Pathogen: disease-causing agents 2. 2 ways bacteria cause disease a. Break down tissues for food b. Release toxins 3. Many can be prevented with vaccines; many can be treated with antibiotics

D.Human Uses of Bacteria 1. Food – cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut 2. Industry – cleaning up oil spills, mining minerals, synthesizing drugs

3. Bacteria live in our digestive tract to help in digestion (called normal flora) Billions of bacteria live in each of us. If we could weigh all the bacteria in the gastrointestinal tract, it would amount to about three and one-half pounds.

E.Controlling Bacteria 1. Sterilization: destroy bacteria by subjecting them to great heat or chemicals a. Boiling, frying, steaming can all kill bacteria b. Disinfectant chemical solutions can be used in homes and hospitals 2. Refrigeration – bacteria grow slowly at low temperatures

III. Viruses A.Viruses: particles of nucleic acid and protein 1. Nucleic acid = DNA or RNA that contains instructions for making new copies of the virus 2. Capsid: outer protein coat

B.Viral Infection 1. Infect cells and replicate inside host cell 2. Bacteriophage: viruses that infect bacteria

3. 2 types of viral infections a. Lytic infection: virus enters cell, make copies of itself and causes the cell to burst b. Lysogenic infection: virus embeds its DNA into DNA of host and is replicated with host cell’s DNA

C.Viruses and Disease 1. Many viruses can be prevented through the use of vaccines (polio, measles, influenza) measles, influenza) 2. Oncogenic viruses cause cancer 3. Retroviruses contain RNA 4. Prions contain no DNA or RNA, only protein

polio

Measles

Regulation of cell cycles is of key importance in human papilloma virus (HPV)-associated cervical carcinogenesis

Retroviruses HIV

Prions Mad cow disease

QUIZ Next class!