Bacteria and Viruses Chapter 20. 20.1 - Bacteria Prokaryotes – single-celled organisms that do not...
-
Upload
wesley-hudson -
Category
Documents
-
view
218 -
download
1
Transcript of Bacteria and Viruses Chapter 20. 20.1 - Bacteria Prokaryotes – single-celled organisms that do not...
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
Plasmid
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
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