Uploaded by c.butler1998

Chapter 27

advertisement
Cell-Surface Structures
• cell wall
– maintains cell shape,
– protects the cell
– prevents bursting in a hypotonic environment
– contains peptidoglycan (sugar, amino acids)
– may have lipopolysaccaride outer membrane
© 2011 Pearson Education, Inc.
• Gram stain technique
– classify bacteria by cell wall composition
– Gram-positive • large amount of peptidoglycan
– Gram-negative • less peptidoglycan
• outer membrane that can be toxic
© 2011 Pearson Education, Inc.
• Antibiotics target peptidoglycan
– damages cell wall
• Gram-negative bacteria
– more likely to be antibiotic resistant
• Capsule
– polysaccharide or protein layer covers many
prokaryotes
© 2011 Pearson Education, Inc.
• capsule
– dense
• sticky layer (glycocalyx)
– not dense
• fimbriae
– hair like appendage
– sticks to surfaces
• pili
– sex appendage
– transfer of DNA
4
Motility (taxis)
• Flagella
– proteins
– evolved independently in bacteria and archae
• 3 main parts
– motor
– hook
– filament
© 2011 Pearson Education, Inc.
Figure 27.6
Flagellum
Filament
Hook
Motor
Cell wall
Plasma
membrane
Rod
Peptidoglycan
layer
20 nm
7
8
Internal Organization and DNA
• Prokaryotic cells : simple
– less DNA
– circular chromosome
• located in nucleoid
– plasmids
• smaller rings of DNA
© 2011 Pearson Education, Inc.
• antibiotics
– inhibit bacterial growth
– blocks protein synthesis
10
Reproduction and Adaptation
• Reproduce quickly
– binary fission
– can divide every 1–3 hours
• Endospores
– metabolically inactive
– harsh environments
– does contain DNA,
© 2011 Pearson Education, Inc.
Bacteria Summary: 3 key features
• All Bacteria
– tiny
– ubiquitous
– metabolically diverse
• Reproduce by binary fission
• Short generation times
26
12
• High genetic variation
– Rapid reproduction
– Mutation
– Genetic recombination
© 2011 Pearson Education, Inc.
Rapid Reproduction and Mutation
• Reproduce by binary fission
– offspring cells are generally identical
• Mutation rates
– low
– accumulate rapidly in a population
• High diversity from mutations
– allows for rapid evolution
© 2011 Pearson Education, Inc.
Genetic Recombination
• Genetic recombination
– combining of DNA from two sources
• done by
– transformation
– transduction
– conjugation
• DNA from different species
– horizontal gene transfer
© 2011 Pearson Education, Inc.
• transformation
– uptake of foreign DNA
• transduction
– movement of genes between bacteria by
bacteriophages
• conjugation
– genetic material transfer between bacterial
cells
© 2011 Pearson Education, Inc.
Conjugation and Plasmids
• In bacteria
– DNA transfer is one way
– donor cell attaches to recipient by a pilus
– F factor
• piece of DNA making the pilus
© 2011 Pearson Education, Inc.
Figure 27.12
The F Factor as a Plasmid
• During conjugation
– cells with F factor
• function as DNA donors
– cells without the F factor
• function as DNA recipients
© 2011 Pearson Education, Inc.
20
The F Factor in the Chromosome
• F factor recipient
– recombinant bacterium
– DNA from 2 different cells
© 2011 Pearson Education, Inc.
R Plasmids and Antibiotic Resistance
• R plasmids
– carry genes for antibiotic resistance
• Antibiotics
– kill sensitive bacteria
• no specific R plasmids
© 2011 Pearson Education, Inc.
• natural selection
– resistance increases in a population
exposed to antibiotics
• antibiotic-resistant strains
– becoming more common
47
23
• Prokaryotes categorized by how they obtain
energy and carbon
–
•
–
•
–
Phototrophs
obtain energy from light
Chemotrophs
obtain energy from chemicals
Autotrophs
– require CO2 as a carbon source
– Heterotrophs
• require an organic nutrient for carbon
© 2011 Pearson Education, Inc.
• Energy and carbon sources are combined to give
four major modes of nutrition:
–
–
–
–
Photoautotroph
Chemoautotroph
Photoheterotroph
Chemoheterotroph
© 2011 Pearson Education, Inc.
Table 27.1
• Prokaryotes and O2
–
•
–
•
•
–
•
Obligate aerobes
require O2 for cellular respiration
Obligate anaerobes
poisoned by O2
use fermentation or anaerobic respiration
Facultative anaerobes
survive with or without O2
© 2011 Pearson Education, Inc.
Nitrogen Metabolism
• Nitrogen produces
– amino acids
– nucleic acids
• Prokaryotes can metabolize nitrogen in a variety
of ways
– Nitrogen fixation
• converts atmospheric nitrogen (N2) to
ammonia (NH3)
© 2011 Pearson Education, Inc.
Metabolic Cooperation
• In the cyanobacterium Anabaena
– photosynthetic cells
– nitrogen-fixing cells (heterocysts)
– exchange metabolic products
• nitrogen
• carbohydrates
© 2011 Pearson Education, Inc.
Molecular systematics
• prokaryotic taxonomy
– based on phenotypic criteria
• molecular systematics
– analyses hereditary molecular differences
– split prokaryotes into
• bacteria
• archaea
© 2011 Pearson Education, Inc.
Archaea
• Archaea share certain traits
– bacteria
– eukaryotes
© 2011 Pearson Education, Inc.
Table 27.2
• Extremophiles - live in extreme environments
– Extreme halophiles
• highly saline environments
– Extreme thermophiles
• very hot environments
© 2011 Pearson Education, Inc.
• Methanogens
– swamps and marshes
– produce methane as a waste product
– strict anaerobes
– poisoned by O2
© 2011 Pearson Education, Inc.
Bacteria
• Bacteria
– vast majority of prokaryotes
– diverse nutritional types
– majority are decomposers
© 2011 Pearson Education, Inc.
Proteobacteria
• gram-negative bacteria
– photoautotrophs
– chemoautotrophs
– heterotrophs
• anaerobic and aerobic
© 2011 Pearson Education, Inc.
Subgroup: Alpha Proteobacteria
• Rhizobium
– in nodules of legumes
– convert atmospheric N2
• Agrobacterium
– genetic engineering
– tumors in plants
© 2011 Pearson Education, Inc.
Subgroup: Beta Proteobacteria
• Nitrosomonas
– converts NH4+ to NO2–
© 2011 Pearson Education, Inc.
Subgroup: Gamma Proteobacteria
• pathogens
– Legionella
– Salmonella
– Vibrio cholerae
– Escherichia coli
© 2011 Pearson Education, Inc.
Subgroup: Delta Proteobacteria
• slime-secreting myxobacteria
© 2011 Pearson Education, Inc.
Subgroup: Epsilon Proteobacteria
• Campylobacter
– blood poisoning
• Helicobacter pylori
– stomach ulcers
© 2011 Pearson Education, Inc.
Chlamydias
• Obligare intracellular parasite
– Chlamydia trachomatis
• blindness
• non-gonococcal urethritis
– STD
© 2011 Pearson Education, Inc.
Spirochetes
• helical heterotrophs
• Some are parasites
– Treponema pallidum
• syphilis
– Borrelia burgdorferi
• Lyme disease
© 2011 Pearson Education, Inc.
• Cyanobacteria
– photoautotrophs
– photsynthesis
– generate O2
© 2011 Pearson Education, Inc.
• Gram-positive bacteria
– Actinomycetes
– decompose soil
– Bacillus anthracis
– anthrax
– Clostridium botulinum
– botulism
– Staphylococcus and Streptococcus
– Mycoplasms
– smallest known cells
© 2011 Pearson Education, Inc.
Chemical Recycling
• Chemoheterotrophic prokaryotes
– function as decomposers
– may increase / decrease the availability of
nitrogen, phosphorus, and potassium
– may be pathogenic
© 2011 Pearson Education, Inc.
Ecological Interactions
• Symbiosis
– two species live in close contact:
– larger host
– smaller symbiont
© 2011 Pearson Education, Inc.
• mutualism
– both organisms benefit
• commensalism
– one organism benefits while neither harming
nor helping the other in any significant way
• parasitism
– parasite harms but does not kill its host
– called pathogens
© 2011 Pearson Education, Inc.
Mutualistic Bacteria
• Human intestines
– 500–1,000 species
– break down food
© 2011 Pearson Education, Inc.
• Pathogenic bacteria
– half of all human diseases
•
•
•
•
•
•
•
•
Lyme disease
Syphilis
Tuberculosis
Pneumonia
Salmonella
Diptheria
Typhoid fever
Leprosy
© 2011 Pearson Education, Inc.
• Pathogenic bacteria
– release exotoxins or endotoxins
• Exotoxins
– bacteria may not be present
• Endotoxins
– released when bacteria die
– cell walls break down
© 2011 Pearson Education, Inc.
Property
Exotoxins
Bacterial Source
Gram +, Gram -
Location in bacterium
Cytoplasm
Ability to form a toxoid
Generally
Toxicity
Very potent - some are
most potent toxins
known
Endotoxins
Gram - only
Outer membrane
No
Not very potent
52
• Horizontal gene transfer
– spread genes associated with virulence
– potential weapons of bioterrorism
• Tularemia
• Anthrax
• Botulism
• Bubonic plague
© 2011 Pearson Education, Inc.
• Prokaryotes
– bioremediation
• remove pollutants from the environment
• Produce
– vitamins
– antibiotics
– hormones
– ethanol
© 2011 Pearson Education, Inc.
Download
Random flashcards
Marketing

46 Cards

African nomads

18 Cards

Ethnology

14 Cards

Create flashcards