Transcript Prokaryotes- Ch. 16

Prokaryotesmost numerous living organism group
Biology Exploring LifeChapter 16
Tree of Life- 3 groups
Yellow = Bacteria Green = Archaea Blue= Eukarya
Bacteria vs Archaea
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Environment/habitatRNA polymerasePresence of intronsEffects of AntibioticsCell wall structure
– Presence of peptidoglycan
What is Peptidoglycan?
• A lattice structure in the bacterial cell wall.
– linear chains of alternating amino sugars
• N-acetylglucosamine and N-acetylmuramic acid
– short peptide chains of three to five amino acids
– The peptide chains form cross-links
• resulting in a 3D mesh-like structure.
• Function– Strength
– Counteracts the osmotic pressure of the cytoplasm.
– Involved in binary fission during bacterial cell
reproduction.
Peptidoglycan Structure
Basic Bacterial Cell
Bacteria have a basic cell structure that includes a cell wall, plasma membrane, ribosomes, DNA that
is not enclosed in a membrane, pili, and flagella for movement.
Classification- Shapes
3 main shapes
1. Coccus ,cocci- circular/spherical
– Arrangement of cells– Pairs, chains, clusters, tetrads
– Examples- prefix names
• Diplococci- 2 cells
• Streptococci- chain /string
cells
• Staphylococci- cluster-grapelike
• Sarcina- tetrad
Gram Stain Examples of Cocci
Staphylococcal infections:
blisters, boils, systemic infections
MRSA-
Shapes2. Bacillus, bacilli- rod-shaped
– Various forms -short or long
– Single or in chains
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E. coli
Bacillus subtilus
Lactobacillus vaginalis
Pseudomonas aeruginosa
Gram Stain Gallery of Bacilli
Pseudomonas aeruginosa
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grows at 42 C.
Hot tub folliculitis
Shapes3. Spirillum, spirilli- spiral shaped bacteria
• Examples- spirochetes
– Treponema pallidum• syphilus- STD
– Borrelia burgdorferi• lyme disease
Lyme disease caused by the bacterium, Borrelia
burgdorferi
Transmitted to humans by bite of infected blacklegged ticks.
Most common vectors - Ixodes scapularis ( common deer tick )
has also been carried by the Lone Star tick,
Most commonly found in Northeastern and North Central United States.
Typical symptoms - fever, headache, fatigue, and a characteristic skin rash called erythema
migrans.
Untreated, infection can spread to the heart, the joints and the nervous system.
Lyme disease is often diagnosed based on the characteristic rash (bull’s eye) and an
exposure to infected ticks
Borrelia burgdorferi is often diagnosed using an enzyme linked immunosorbent assay with
Western blot confirmation
2. Bacterial Cell Wall structures
• Different from plants, fungi and protists
• Have peptidoglycan
• Bacteria are divided into 2 main groups based
on differences in their cell walls.
– The amount of peptidoglycan
– If they have an outer lipid membrane
• Gram Stain – 1884- Hans Christian Gram
Differential stain
• Gram Positive Bacteria
• Gram Negative Bacteria
Gram Positive vs Gram Negative
Cell walls
Gram Positive Bacteria
• Cell wall consists of a thick outer wall of
peptidoglycan
• Stain blue/purple in the gram stain test.
• Retain(keep) the initial crystal violet stain
color.
• Do not decolorize with alcohol.
• Are more sensitive to Penicillin antibiotics.
Gram Negative Bacteria
• Two parts to their cell wall
– An Inner thin layer of peptidoglycan
– An Outer lipid membrane.
• Do not retain (keep) the initial crystal violet
stain.
• They are decolorized due to the outer lipid
membrane
• They pick up the 2nd stain ( counterstain)
safranin and stain pink/red.
Gram Stain Procedure
• See handout for procedure
• Refer to handout for results after each step.
Gram Positive vs Gram Negative
Cell walls
Importance of the Gram Stain
• The key test to differentiate bacteria.
• Can be done rapidly- a “STAT” test
• Used to divide bacteria into one of two main
groups based on cell wall type.
• Used to determine shape (morphology) of
bacteria
• Used to presumptively identify the infectious
bacterium.
• Used by physicians to prescribe antibiotics based
on type of cell wall.
• Key if unable to grow the bacterium
3. Motility- movement
• Move toward or away from signals
– Food, light, oxygen, toxins
• Flagella– Anchored in plasma membrane and cell wall.
– Bacterial flagella- different from eukaryotes
– Different types of flagella- based on numbers and location on
bacterial cell.
– bacilli and spirilli are motile
– Cocci are nonmotile- do not move
• Pili- allow bacteria to adhere to surfaces and each other.
• Slime layers-
Different types of flagella
• monotrichous = single flagellum at one end.
amphitrichous = flagella at both ends
lophotrichous = tuft of many flagella at one end or both ends.
peritrichous = flagella all around the cell
• Motility can be identified in a couple of different ways:
– the hanging drop wet mount- look for directional movement.
– Semi-solid motility agar- stab and incubate overnight.
4. Environment
• Aerobic bacteria- need oxygen to survive.
• Anaerobic bacteria- live without oxygen,
strict anaerobes- cannot tolerate oxygen.
• Most bacteria can live in both environments– Facultative anaerobes.
Reproduction in Bacteria
• Binary fission- clones-results in two identical cells
– Mutations can occur in copying of DNA
• Simpler than mitosis
• Rapid, continuous, ~ every 20 minutes, exponential growth1,2,4,8,16,32.
• Refrigeration slows down rate of reproduction
Bacterial Growth Curve- 4 stages- Typical S curve.
1. lag phase- start up
2. log-logarithmic phase- rapid exponential growth
3. stationary phase- limiting factors( food, water, space, waste)
– Carrying capacity =most numbers of population due to limiting factors
– Death rate= birth rate.
4. Death phase.
Review Pg 376- Question # 18.
3 methods of Genetic Variation
• Transformation- bacteria takes up DNA from
environment
• Conjugation- 2 bacterial cell join and transfer
genetic material- plasmids
• Transduction- when viruses (bacteriophage)
infect bacteria with their genes.
Transformation and Conjugation
Transduction
Endospores
• Special resting cells.
– Thick protective coat
– surrounding the chromosome, very resistant.
• Survival in unfavorable conditions
– Lack of water, nutrients, heat, cold, toxins
– Can last for years.
– Absorb water when favorable environment and grow
again.
• Example- Bacillus anthracis- anthrax
Modes of Nutrition
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How organisms obtain energy and carbon atoms.
Energy by photosynthesis –light - use prefix photo.
Energy from chemical sources – inorganic or organic- use prefix chemo.
Autotrophs obtain carbon atoms from carbon dioxide.
Heterotrophs obtain carbon from existing organic molecules (such as those in
food).
• Bacteria- most numerous organisms- found in all 4 modes
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Photoautotrophs- carry out photosynthesis- plants, plant like protists, and
photosynthetic bacteria
Chemoautotrophs use carbon dioxide as a carbon source, but they extract energy
from inorganic substances such as hydrogen sulfide or ammonia. All
chemoautotrophs are prokaryotes.
Photoheterotrophs use light energy to make ATP but obtain their carbon in
organic form. This mode of nutrition is only found in certain prokaryotes.
Chemoheterotrophs consume organic molecules for both energy and carbon.
Found in many bacteria, animal and fungi like protists, fungi, and animals.
We are chemoheterotrophs.
4 categories of nutrition
• Plants, algae, prokaryotes
• Prokaryotes only
• Prokaryotes only
• Prokaryotes, animal and fungus like
protists, all fungi, all animals
Cyanobacterium
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Photoautotrophs
Ancient
Oxygen released in photosynthesis
Oxygen revolution
– Extinction of some
– Survival in anaerobic environments
– Adaptation for organisms that can survive in oxygenaerobic organisms- many prokaryotes, nearly all
eukaryotes. Oxygen used to make most amounts of ATPenergy.
Important functions of prokaryotes
16.3
• Chemical recycling
• Decomposers- break down organic waste and
dead organisms in environment.
– Returns carbon to atmosphere as CO2.- carbon
cycle
• Nitrogen cycle- nitrogen fixing bacteria- N2NO3 and ammonium to be used by plants.
Bioremediation
• Use of prokaryotes to remove pollutants from water,
air, and soil.
• Sewage treatment
• Pseudomonas sp.- oil degradation on beaches.
• Thiobacillus- lives in acidic mine environments,
removes lead and mercury in mine runoff.
• Making vitamins and antibiotics
• Genetic engineering- making protein products.
Pathogenic Bacteria
• Pathogens- disease causing microorganisms.
• Body defenses- examples– Skin, normal biotic flora
• Bacteria poisons- toxins
– 2 types
• Secreted by the bacterial cell- exotoxin
– Food poisoning- Clostridium botulinum
– Staphylococci
• Toxin is part of cell wall
– Drop in blood pressure-shock
– Salmonella food poisoning
Defenses against disease
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Washing hands
Care in food prep.
Water control
Good hygiene
Vaccines
Antibiotics
– Major Health Concern- resistance of bacteriamutations and genetic variation