Embed Size (px)
DESCRIPTION
Citation preview
Bacteria and Viruses
Chapter 19
19.1 Bacteria
Come in many shapes and sizes
Most common microorganisms are prokaryotes
Average size of 1-5 micrometersCompared to eukaryotic cells that are 10-
100 micrometers in diameter
Classifying Prokaryotes
EubacteriaLargest prokaryote DomainCell wall of a carbohydrate- PeptidoglycanCell membrane around cytoplasmSome have an extra cell wall on the
outside to resist damage
Classifying Prokaryotes
ArchaebacteriaLack nucleiHave cell walls without peptidoglycanAre chemically different from EubacteriaMany live in extremely harsh environments
Identifying Prokaryotes
ShapesBacilli- Rod shapedCocci- Spherical shapedSprilla- spiral and cork-screw shaped
Colorized SEM 9,000 Colorized SEM 12,000
Identifying Prokaryotes
Cell wallsGram staining used to tell them apartGram+ bacteria look purpleGram- bacteria look pink
Identifying Prokaryotes
MovementFlagellaLash, snake or spiral forward They do not move at all
Metabolic Diversity
HeterotrophsChemoheterotrophs: must take in organic
molecules for energy and carbon
Photoheterotrophs: Use sunlight for energy but need organic compounds for a carbon source
Metabolic Diversity
AutotrophsChemoautotrophs: perform
chemosynthesis to make carbon from carbon dioxide. Does not require sunlight
Photoautotrophs: use light to convert carbon dioxide and water into carbon compounds and oxygen gas.
Getting Energy Bacteria need a constant supply of energy
Obligate aerobes- require constant supply of oxygen
Obligate anaerobes- need no oxygen, for some oxygen will kill it
Facultative anaerobes- survive with or with out oxygen
Growth and Reproduction
Binary fission
Conjugation
Spore formation
Importance of Bacteria
DecomposersBreak down dead matter
Nitrogen FixersConverts nitrogen into a form plants can
use
Humans use Bacteria
19.2 Viruses
What is a virus?Particles of nucleic acid and proteins
Core made up of DNA or RNA surrounded by a capsid
Need to infect a
living host to reproduce
Head
Tail
Tail fiber
DNA
300,
000
Video on Lytic and Lysogenic Cycle
http://www.youtube.com/watch?v=gU8XeqI7yts&feature=related
Viral Infection
Lytic CycleVirus attaches to host cellInjects its DNAHost makes RNA from viral DNACell begins to make copies of virusNew viruses formHost cell bursts
Viral Infection
Lysogenic CycleVirus attaches to host cellInjects DNAViral DNA incorporates itself into the host
DNAViral DNA can be dormantOnce it becomes active, it follows the 4
processes in the lytic cycle
Phage reproductive cycles
Lysogenic bacterium reproducesnormally, replicating the prophageat each cell division
Phage DNA inserts into the bacterialchromosome by recombination
New phage DNA andproteins are synthesized
Phages assemble
Cell lyses,releasing phages
Phage
Attachesto cell
Phage DNA
Phage injects DNA
Many celldivisions
Prophage
Lytic cycle Lysogenic cycle
OR
Bacterialchromosome
Phage DNAcircularizes
Figure 10.17
1
2
3
4
5 6
7
Viral Infections
Retrovirus: Genetic information is RNA
Produces DNA copy and creates a prophage
Example:
HIV/AIDS
Envelope
Glycoprotein
Protein coat
RNA (two identical strands)
Reverse transcriptase
19.3 Diseases Caused by Bacteria and Viruses
Pathogens- disease causing agents
Bacterial Disease
Viral Diseases
Diseases Caused by Bacteria
How does bacteria produce disease?
Damage the cells and tissues by breaking down the cells for food
Releasing toxins (poisons into the body)
Preventing Diseases
Vaccines
Immunity
Antibiotics
Controlling Bacteria
Sterilization
Disinfectants
Proper food storage
Diseases Caused by Viruses
Viruses disrupt the body’s normal equilibrium
Cannot be treated with antibiotics
Viruses can infect humans and plants
Viruslike Particles
Viroids- single stranded RNA molecule with no capsidThey cause diseases in plants
Infect cell and produce more viroids by disrupting the plant metabolism
Viruslike Particles
Prions- contain only protein; no DNA or RNAThey cause diseases in animals and
humans
Prions clump and cause normal protein to clump with it- creating new prions
