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Bacteria
Prokaryotes-single-celled organisms without an nucleus
Two kingdomsEubacteria-live anywhere; cell wall of
peptidoglycanArchaebacteria-live in extreme
environments; no peptidoglycan; most live without oxygen
Prokaryotes
Identified byShape
Cocci-roundSpirilli-spiral shapedBacilli-rod
Chemical nature of cell wallsThick peptidoglycan stains purple; thin walls
stain pinkMovement: flagella, twisting, secretionsMethod of obtaining energy
Metabolic diversity
HeterotrophsChemoheterotrophs-take in organic
chemicals for energy and carbonPhotoheterotrophs-photosynthesize for
energy but take in chemicals for carbonAutotrophs
Photoautotrophs-use light for energy and carbon
Chemoautotrophs-use chemicals for energy and carbon
Releasing energy
Occurs by cell respiration, fermentation, or both
Obligate aerobes-require oxygen for survival
Obligate anaerobes-do not need oxygen and are often killed in oxygen
Facultative anaerobes-can live with or without oxygen
Bacterial reproduction
Binary fission-1.cell doubles in size; 2.replicates its DNA; 3.cell divides in half to make 2 new cells (identical)
Conjugation-1.one bacterium hooks to another bacterium with a pilus; 2. genes are exchanged between the two cells
Spore formation-thick coverings or endospores form to protect the bacterium in unfavorable conditions
Importance of bacteria
Help maintain the living worldDecomposers-recycle nutrients in the
environment (decaying organisms, sewage)
Nitrogen fixers-convert gaseous nitrogen to a useable form
Industrial uses-used to make food products, remove waste, digest petroleum, mine minerals
Viruses
Particles of nucleic acid, protein, and sometimes lipids
Reproduce only by infecting other cells
Differ in size and structureHighly specific in cells they infect
Typical virus structure
Capsid- protein coat, includes proteins that enable virus to enter a host cell
Nucleic acid core- made of DNA or RNA but not both
Viral infection: Lytic
1. virus attaches to outside of cell and inserts its nucleic acid into the host
Viral DNA destroys host DNA and takes over the cells metabolism
Host is used to make new viral particles, DNA and protein
Host bursts open to release new viruses
Viral infection: Lysogenic
1. virus attaches to host and inserts its nucleic acid
Viral DNA is inserted into the host DNA and is replicated with host DNA for an unlimited amount of time
Viral DNA removes itself from host DNA and destroys host DNA
New viral particles are producedCell bursts open and releases new
viruses
Retroviruses
Contain only RNAAfter infection, produce a DNA copy
of their RNADNA is inserted into host DNACan be dormant for unlimited
amount of timeIncludes some cancers and HIV
Viruses are NOT alive
Viruses must infect another cell in order to reproduce
Use host’s respiration, nutrition, and other functions
Are parasites
Diseases
Pathogens-disease causing agentsDisease – conflict between the
pathogen and the host; results when infection causes harm to the host; interferes with the host’s ability to obtain nutrients and energy needed to function properly
Bacterial disease in humans
First discovered by Louis PasteurSome bacteria damage cells and
tissues directlySome bacteria release toxins that
travel through the blood then damage tissues
Preventing bacterial disease
Vaccines-preparation of weakened or killed pathogens that is injected into the body to stimulate the immune system
Antibiotics-compounds that block the growth and reproduction of bacteria
Controlling bacteria
Sterilization by heat-destroys most bacteria since most cannot survive at high temperatures
Disinfectants- chemicals used to kill bacteria
Food preparation and storage-canning or using preservatives such as salt, sugar, pickling
Antibacterials
Added to most soaps and cleaning agents
Becoming problematicAllowing many bacteria to become
resistant to antibacterial agentsMakes bacteria harder to kill with
medications
Viral disease
Disrupt normal equilibrium in the cells
Specific to species they infectOnly be prevented with vaccines
before infection
Viroids
Single-stranded RNA molecules with no capsid
Enter cell and direct synthesis of new viroids
Infect plants and disrupt metabolism, stunt growth