Bacteria and Viruses Chapter 20

20.1 - Bacteria Prokaryotes – single-celled organisms that do not have membrane bound organelles Has three shapes: Bacillus – rod-shaped Coccus – sphere-shaped Spirillum – spiral-shaped

Bacterial Structures Plasmid – a circular DNA molecule in bacteria Ribosome – site of protein synthesis Cell wall Cell membrane

Bacterial Structures Flagella – long whiplike projection that moves side to side Cytoplasm – gel-like substance found inside the cell Ring of DNA

Obtaining Energy and Nutrients Photoautotrophs – organisms that get their energy from sunlight through photosynthesis Ex. – cyanobacteria Chemoautothrophs – the only organisms that can get their energy from inorganic sources Inorganic – does not contain carbon atoms Heterotrophs

Reproduction Binary fission – reproduce by asexual reproduction A single cell divides into two identical cells Conjugation – occurs when two bacteria exchange genetic material

20.2 - Viruses Viruses are not considered living because they can’t reproduce on their own, and they can’t grow

Viral Structures Nucleic acid – The genetic material of a virus can be either DNA or RNA Capsid – the protein coat Envelope – a membrane surrounding the capsid Envelope

Viral Structures Tail fibers – function like a tiny syringe which injects the viral DNA into its bacterial host Bacteriophage – viruses that infect bacteria Bacteriophage

Reproduction Lytic cycle – viral replication that results in the destruction of a host cell and the release of many new virus particles

Reproduction Lysogenic cycle – viral replication in which viral genetic information is made without immediately destroying the host cell Viruses undergo lysogentic cycles can remain dormant

Viroids and Prions Viroid – a single strand of RNA that has no capsid Viroids cause abnormal development and stunted growth in plants

Viroids and Prions Prions – misshapen versions of proteins that are found in the brain They attach to normal proteins and cause them to take on the shape of the prion

20.3 – Bacteria, Viruses, and Humans

Bacteria and the Environment Bacteria produce oxygen, make nitrogen available to other organisms, and help decompose dead organisms.

Bacteria and Industry Foods, such as pickles, soy sauce, and sourdough bread, are made by using bacteria Bacteria is used in cleaning up oil spills and in sewage treatment plants

Koch’s Postulates Robert Koch, a German physician, developed a technique for diagnosing a pathogen Pathogen – an organism or virus that causes disease

Bacterial Diseases Bacteria can cause disease by producing toxins and by destroying body tissues Toxins – poisonous chemicals Ex. of toxins – Foods contaminated with bacteria can cause food poisoning. Ex. of destroying body tissues – necrotizing fasciitis

Antibiotic Resistance Antibiotics – chemicals that inhibit the growth of or kill bacteria Antibiotic resistance – the ability of bacteria to tolerate antibiotics

Antibiotic Resistance Penicillin was used for most bacterial infections Do not overuse antibiotics Ex. of resistance – hand sanitizer

Viral Diseases Because viruses enter the host cells to reproduce, it’s difficult to develop a drug that kills the virus without harming the living cell. Antibiotics are not designed to kill viruses Vaccine – a weakened form of a pathogen that prepares the immune system to recognize and destroy the pathogen Ex. – flu shot