19 Bacteria And Viruses

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