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Ch27 Bacteria and Archaea (27.1 structural and functional adaptations…
Ch27 Bacteria and Archaea
27.1 structural and functional adaptations contribute to prokaryotic success
cell surface structure
flagella
structures used by most motile bacteria for propulsion; many species can move toward or away from certain stimuli
cell wall
gram-negative bacteria
more complex, outer membrane
contains lipopolysaccharides
gram-positive bacteria
simple cell walls, thick layer of peptidoglycan
gram stain
is to show differences in cell wall composition
internal organisation
no nucleus or other membrane-enclosed organelles; usually no complex compartmentalization
circular chromosome
often accompanied by smaller rings of DNA called
plasmids
capsule
sticky layer of polysaccharide or protein that can help cell adherence and/or evasion of a host's immune system
pilus
appendage that facilitates conjugation
fimbriae
hairlike appendages that help cells stick to other cells or to a substrate
reproduction
Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours under optimal conditions
They are small
They reproduce by binary fission
They have short generation times
motility
About half of all prokaryotes exhibit
taxis
, the ability to move toward or away from a stimulus
comparison b/c prokaryotes and eukaryotes on membrane compartmentalisation
prokaryotes must have:
nucleoid(DNA), ribosomes, cytoplasm, cell wall, plasma membrane
eukaryotes have:
DNA in nucleus, membrane-enclosed organelles: nucleus, Golgi, ER, mitochondria, lysosomes in animal cells, chloroplast in plant cells
prokaryotes and eukaryotes both have:
chromosomes, ribosomes, cytoplasm, cell wall, plasma membrane
27.2 rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes
reproduce asexually; offspring cells are generally identical
Rapid reproduction
Mutation
Genetic recombination
the combining of DNA from two sources, contributes to diversity
Transformation
A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation
Transduction
Transduction is the movement of genes between bacteria by phages
Conjugation
is the process where genetic material is transferred between prokaryotic cells
A piece of DNA called the F factor is required for the production of pili
Cells containing the F plasmid function as DNA donors during conjugation
R Plasmids and Antibiotic Resistance
R plasmids carry genes for antibiotic resistance
Antibiotics kill sensitive bacteria, but not bacteria with specific R plasmids
Through natural selection, the fraction of bacteria with genes for resistance increases in a population exposed to antibiotics
27.3 diverse nutritional and metabolic adaptations have evolved in prokaryotes
Table 27.1
heterotroph
chemoheterotroph
energy source: light
carbon source: organic compounds
types of organisms: many prokaryotes, , and protists;
fungi; animals; some plants
photoheterotroph
energy source: organic compounds
carbon source: organic compounds
types of organisms: unique to certain aquatic and salt-loving
prokaryotes, Rhodobacter, Chloroflexus
autotroph
chemoautotroph
energy source: inorganic chemicals
carbon source: CO2, HCO3-, or related compound
types of organisms: unique to certain prokaryotes, Sulfolobus
photoautotroph
energy source: light
carbon source: CO2, HCO3-, or related compound
types of organisms: photosynthetic prokaryotes, cyanobacteria;
plants; certain protists, algae
27.4 prokaryotes have radiated into a diverse set of lineages
Table 27.2 A comparison of the three domains of life
Archaea
absent in nuclear envelope, membrane-enclosed organelles and peptidoglycan in cell wall
present in circular chromosome
membrane lipids: some unbranched hydrocarbons
RNA polymerase: several kinds
initiator amino acid for protein synthesis: methionine
introns in genes and histones associated with DNA: present in some genes
response to the antibiotics streptomycin and chloramphenicol: growth not inhibited
growth at temperatures >100 C: some speices
Eukarya
absent in circular chromosome and peptidoglycan in cell wall
present in nuclear envelope, membrane-enclosed organelles and histones associated with DNA
membrane lipids: unbranched hydrocarbons
RNA polymerase: several kinds
initiator amino acid for protein synthesis: methionine
introns in genes and histones associated with DNA: present in many genes
response to the antibiotics streptomycin and chloramphenicol: growth not inhibited
growth at temperatures >100 C: no
Bacteria
absent in nuclear envelope, membrane-enclosed organelles and histones associated with DNA
present in peptidoglycan in cell wall, circular chromosome
membrane lipids: unbranched hydrocarbons
RNA polymerase: one kind
initiator amino acid for protein synthesis: formylmethionine
introns in genes: very rare
response to the antibiotics streptomycin and chloramphenicol: growth usually inhibited
growth at temperatures >100 C: no
