Prokaryotes 1. 1. Classifying Prokaryotes 2. 2. Identifying Prokaryotes 3. 3. Role in the...
-
Upload
diana-york -
Category
Documents
-
view
224 -
download
2
Transcript of Prokaryotes 1. 1. Classifying Prokaryotes 2. 2. Identifying Prokaryotes 3. 3. Role in the...
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.