Unit 6 Microorganisms & Fungi

Ch. 19 Bacteria & Viruses

Bacteria

Prokaryotes - unicellular organisms that lack a nucleus The smallest & most common microorganism

Classifying Prokaryotes

Prokaryotes are divided into 2 separate kingdoms: eubacteria & archaebacteria

Classifying Prokaryotes

Eubacteria are surrounded by a cell wall that protects the cell from injury & determines its shape

Classifying Prokaryotes

Archaebactertia live in extremely harsh envrionments May be found in oxygen-free envrion. like

thick mud & the digestive tracts of animals Some live in salty environ. like Utah’s Great

Salt Lake Others are found in hot springs where temps.

approach the boiling point of water

Identifying Prokaryotes

Prokaryotes are identified by characteristics such as shape, the chemical nature of their cell walls, the way they move, & the way they obtain energy

Identifying Prokaryotes

Bacilli - rod-shaped bacteria

Cocci - round bacteris

Spirilla - spiral-shaped bacteria

Identifying Prokaryotes

2 different types of cell walls are found in eubacteria

Gram staining is a method used to tell them apart

Gram-positive bacteria have a peptidoglycan wall

Gram-negative bacteria have a lipid layer

Metabolic Diversity

Chemoheterotrophs - most heterotrophic prokaryotes take in organic molecules for both energy & a supply of carbon Includes most animals, even humans

Metabolic Diversity

Photoheterotrophs - heterotrophic prokaryotes that are photosynthetic, using sunlight for energy, but also need to take in organic compounds as a carbon source

Metabolic Diversity

Photoautotrophs - autotrophs that use light energy to convert carbon dioxide & water to carbon compounds & oxygen Found where light is plentiful

Metabolic Diversity

Chemoautotrophs - prokaryotes that can perform chemosynthesis Like photoautotrophs, they make organic carbon

molecules from carbon dioxide However, they do not require light as a energy source They use energy directly from chemical reactions

involving ammonia, hydrogen sulfide, nitrites, sulfur, or iron

Metabolic Diversity

Obligate aerobes - organisms that require a constant supply of oxygen in order to live

Obligate anaerobes - bacteria that must live in the absence of oxygen

Facultative anaerobes - bacteria that can survive with or without oxygen

Growth & Reproduction

Binary fission - when a bacterium has grown so that it has nearly doubled in size, it replicates (copies) its DNA & divides in half, producing 2 identical “daughter” cells

Growth & Reproduction

Conjugation - when a hollow bridge forms between 2 bacterial cells, & genes move from 1 cell to another

Growth & Reproduction

Endospore - a type of spore that is formed when a bacterium produces a thick internal wall that encloses its DNA & a portion of its cytoplasm Allows some bacteria to survive

harsh conditions like extreme heat, dryness, or lack of nutrients

Importance of Bacteria

Bacteria are vital to maintaining the living world

Some are producers that capture energy by photosynthesis

Others are decomposers that break down the nutrients in dead matter & the atmosphere

Still other bacteria have human uses

Importance of Bacteria

Nitrogen fixation - the process of converting nitrogen gas into a form that plants can use Allows nitrogen atoms to

continually cycle through the biosphere

Certain bacteria produce nitrogen compounds, naturally

Importance of Bacteria

Human uses: Used to clean up oil spills because they digest

petroleum Some remove waste products & poisons from

water Some synthesize drugs & chemicals in genetic

engineering Some live in the human intestine, & make

vitamins that the body cannot produce by itself

What is a Virus?

Virus - particles of nucleic acid, protein, & sometimes, lipids

They can reproduce only by infecting living cells

Viruses enter living cells & use the machinery of

the infected cell to produce more viruses

What is a Virus?

A typical virus is composed of a core of DNA or RNA surrounded by a protein coat

Capsid - a virus’s protein coat, it includes proteins that enable a virus to enter a host cell

Bacteriophages - viruses that infect bacteria

Viral Infection

In a lytic infection, a virus enters a cell, makes copies of itself, & causes the cell to burst

Lytic infection - when the host cell is lysed, or burst open, & destroyed

Viral Infection

In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, & the viral genetic information replicates (copies) along with the host cell’s DNA

Lysogenic infections - when a host cell makes copies of the virus, indefinitely

Prophage - the viral DNA embedded in the host’s DNA

Retroviruses

Retroviruses - viruses that contain RNA as their genetic information

After infecting a cell, they produce a DNA copy of their RNA (working backwards)

Ex.) AIDS

Diseases Caused by Bacteria & Viruses

Pathogens - disease-causing agents

Disease can be considered a conflict between the pathogen & the host

Bacterial Disease in Humans

Bacteria live on & in our bodies, some help us perform essential functions

However, the growth of pathogenic bacteria disrupts the body’s equilibrium by interfering with its normal activities & producing disease

Bacterial Disease in Humans

Bacteria produce disease in 1 of 2 general ways: They damage the cells & tissues of the infected

organism by breaking down the cells for food They release toxins (poisons) that travel

throughout the body interfering with the normal activity of the host

Preventing Bacterial Disease

Vaccine - a preparation of weakened or killed pathogens When injected in the body, sometimes prompts

the body to produce immunity to the disease

Antibiotics - compounds that block the growth & reproduction of bacteria Only effective against BACTERIAL infections

Bacterial Diseases in Animals

Controlling Bacteria

There are various methods used to control bacterial growth, including sterilization, disinfectants, & food processing

Viral Diseases in Humans

Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium

In many viral infections, viruses attack & destroy certain cells in the body, causing the symptoms of disease

Diseases Caused by Viruses