Prokaryotes

1. Classifying Prokaryotes

2. Identifying Prokaryotes

3. Role in the Environment

4. Bacteria and Disease

Classifying Prokaryotes

Eubacteria Larger and more diverse than archaebacteria Live almost everywhere Cell walls contain peptidoglycan

Archaebacteria Live in hostile environments (hot springs, salt

lakes) Cell walls lack peptidoglycan

Archaea are classified into three main groups:

Below: halophiles living in evaporating salt flats. The colors are caused by pigments in their cells.

Halophiles – “salt – loving”

Thermophiles – “heat – loving”

Methanogens – methane users or makers

Thought Question:Thought Question:Prokaryotes such as these halophiles, Prokaryotes such as these halophiles, have unusual metabolisms and occupy have unusual metabolisms and occupy niches that eukaryotes could not survive niches that eukaryotes could not survive in. How does the concept of in. How does the concept of adaptive adaptive radiationradiation help explain why prokaryotes live help explain why prokaryotes live in more diverse habitats than eukaryotes?in more diverse habitats than eukaryotes?

Left: Thermophiles living in a hot spring.

Prokaryote DiversityProkaryote Diversity

The Three Domains of Life - a cladogram based on ribosomal RNA comparisons.

According to this cladogram, which group of bacteria are more closely related to us?

Bacteria often have one of three shapes:

bacilli (rod-shaped)

spirilli (spiral-shaped) cocci (sphere-shaped)

Thought Question:Thought Question:What shape are the What shape are the bacteria on the tip of bacteria on the tip of this needle?this needle?

PeptidoglycanCell wall

Cell membrane

Ribosome

Flagellum DNA Pili

Anatomy of a Bacterium

Plasmid

Unique structures in bacteria:Peptidoglycan – a carbohydrate/protein layer that forms the cell wall (not in archaea)

Flagellum – used for locomotion

Pili – used for attachment

Plasmid – small, circular sequences of DNA, used in “swapping genes”

Peptidoglycan

Flagellum Pili

Plasmid

Gram Staining - a technique used to distinguish between types of eubacteria by measuring the amount of peptidoglycan in the cell wall

Gram positive - bacteria with a thick peptidoglycan cell wall, absorbs a purple colored stain = “gram positive bacteria”

Gram negative - bacteria with a thin peptidoglycan cell wall, masked by an outer membrane, absorbs red colored stain = “gram negative bacteria”

Obtaining Energy Autotrophs

Photosynthesis Cyanobacteria – contain a bluish-green pigment and

chlorophyll, common in aquatic environments Chemosynthesis

Obtain energy directly from inorganic molecules, found around ocean vents

Heterotrophs Can be consumers, parasites, or decomposers

Photoheterotrophs Can capture sunlight for energy Also need organic compounds for nutrition

Growth and Reproduction

Binary fission DNA replicates and cell divides to produce two

identical daughter cells Conjugation

Two cells are joined by a bridge and exchange genes (plasmids) – increases diversity

Spore Formation Occurs when conditions are unfavorable Can survive months to centuries!

Prokaryotes and the “Invention of Sex”

Unlike many eukaryotes, prokaryotes reproduce asexually. Through binary fission (the replication of DNA and the division of one bacterium into two cells) bacteria can typically reproduce much faster than eukaryotes.

A disadvantage with this system is that bacteria do not “mix” genes to produce variable offspring.

To get around this process bacteria evolved conjugation – the copying & “swapping” of genes between cells, especially when the environment is unfavorable.

The mixing of genes between two different individuals is, biologically, sex.

Thought Question:Thought Question:How does conjugation enable bacteria How does conjugation enable bacteria to evolve & adapt to new environmental to evolve & adapt to new environmental conditions?conditions?

Nitrogen fixing bacteria - convert nitrogen gas (N2) in the air to an organic form (ammonia, NH3) , usable by some other living things.

Nitrifying bacteria - convert ammonia to nitrate (NO3), which is usable for plants to make protein.

Decomposing bacteria - break complex organic nitrogen in dead organisms back into NH3).

Denitrifying bacteria - break organic simple nitrogen in dead organisms back into N2 gas.

Prokaryotes and the Nitrogen Cycle

NH3

N2 in Atmosphere

NO3-

and NO2-

Tooth decay

Lyme disease

Tetanus

Tuberculosis

Salmonella food poisoning

Pneumonia

Cholera

Streptococcus mutans

Borrelia burgdorferi

Clostridium tetani

Mycobacterium tuberculosis

Salmonella enteritidis

Streptococcus pneumoniae

Vibrio cholerae

Regular dental hygiene

Protection from tick bites

Current tetanus vaccination

Vaccination

Proper food-handling practices

Maintaining good health

Clean water supplies

Disease Pathogen Prevention

Bacteria infect living organisms by:* Eating the organism’s tissues directly* Releasing toxins

Common Diseases Caused by Bacteria

Viruses

1. Characteristics of a Virus

2. Viral Infection

3. Viruses and Disease

Characteristics of Viruses:

• Viruses are nonliving, infectious particles

(cannot reproduce on their own, cannot obtain energy or feed in any way)

• Viruses are extremely small (on average they are one-thousandth the size of a typical bacterium)

• Vary greatly in structure and shape

• All organisms can be infected by viruses

T4 BacteriophageTobacco Mosaic

Virus Influenza Virus

Head

Tail sheath

DNA

Tail fiber

RNACapsid

Surfaceproteins Membrane

envelope

RNA

Capsidproteins

Virus Structures - all viruses contain a protein capsid (coat), nucleic acid (RNA or DNA), and some means of attaching to and entering a host cell.

Thought Question:Thought Question: Unlike bacteria, viruses cannot be treated with antibiotics since Unlike bacteria, viruses cannot be treated with antibiotics since they lack a peptidoglycan cell wall. Instead, we can only prevent viruses with they lack a peptidoglycan cell wall. Instead, we can only prevent viruses with vaccines – drugs made by destroyed viruses. What part of the virus do you think is drugs made by destroyed viruses. What part of the virus do you think is most important to making a vaccine so the body can “recognize” and destroy the most important to making a vaccine so the body can “recognize” and destroy the virus?virus?

Virus Reproduction:

Thought Question:Thought Question:What organelle do viruses lack that are What organelle do viruses lack that are required for reproduction? Explain.required for reproduction? Explain.

•The proteins of the capsid allow the virus to gain entry through the cell membrane of the host

•Viruses infect a host by injecting their DNA or RNA. Infected cells make copies of the virus’ genetic material instead of its own

•The parasitic virus “hijacks” the cellular machinery of the cell.

Lysogenic cycle – replicates the phage genome without destroying the host. However, the virus is capable of entering the lytic cycle.

Thought Thought Question:Question:

After you have After you have contracted contracted

chicken pox, chicken pox, the virus the virus

resides in your resides in your spinal cord. spinal cord.

Later, the virus Later, the virus can re-emerge can re-emerge

to cause to cause shingles, a shingles, a

disease disease related to related to

chicken pox. chicken pox. Explain this Explain this

relationship in relationship in the context of the context of

viral viral reproduction.reproduction.

Lytic cycle – a phage reproductive cycle that results in the death of the host cell.

Reproductive Cycles of a Virus

Oncogenic viruses

Retroviruses

Adenoviruses

Herpesviruses

Poxviruses

DNA

RNA

DNA

DNA

DNA

cancer

cancer, AIDS

respiratory infections

chickenpox

smallpox

Type of Virus Nucleic Acid Disease

Common Diseases Caused by Viruses

EssaysAfter completing the microbe zoo activity you see one of your friends eating yogurt. Feeling all smart you point out to him that his cup of yogurt contains lactobacillus acidophillus, a type of bacteria. Your friend freaks out a little, throws the yogurt into the trash and starts shouting "Is the Dannon Corporation Crazy! Are they trying to get everyone sick with the flu or something!" Explain to your friend the two major biological problems with his statement. Include the terms bacteria, mutualism, large intestine, lactobacillus, diarrhea, E. coli, vitamin K, viruses, influenza.

In 1928, the first antibiotic, penicillin, was isolated for human use. However, now penicillin is hardly ever prescribed because it is far less effective than it was 75 years ago. Why is this the case? Use the following terms in your answer: population, fitness, variation, resistance, gene pool, adaptation, mutation, environment.