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Chap 27 Masters of Adaptation (27.1 (Cell-surface structure (peptidoglycan…
Chap 27 Masters of Adaptation
27.1
Cell-surface structure
peptidoglycan- a polymer composed of modified sugars cross-linked by short polypeptides.
Gram stain- developed by the 19th century Danish physician Hans Christian Gram, to do this samples are first stained with crystal violet dye and iodine, then rinsed off with alcohol, and finally stained with a red dye such a safranin the enters the cell and binds to its DNA.
Gram-positive- bacteria have relatively simple walls composed of a thick layer of peptidoglycan
gram-negative- bacteria have less peptidoglycan and are structurally more complex, with an outer membrane that contains lipopolysaccharides ( carbohydrates bonded to lipids).
capsule- cell wall of many prokaryotes is surrounded by a sticky layer of polysaccharide or protein.
endospores- a way of withstanding harsh conditions, certain bacteria develop resistant cells, when they lack water or essentail nutrients.
fimbriae- some prokaryotes stick to their substate or to one another by means of hairlike appendages.
pili- appendages that pull two cells together prior to DNA transfer from one cell to the other, sometimes referred to as the
sex
pili*
Motility
taxis- half of prokaryotes are capable of it, a directed movement toward or away from stimulus.
Internal Organization and DNA
nucleoid- unlike eukaryotes, prokaryotes lack a nucleus; their chromosome is located here.
plasmids- typical prokaryotic cell may also have much smaller rings of independently replicating DNA molecules.
27.2
Transformation & Transduction
transformation- genotype and possibly phenotype of prokaryotic cell are altered by the uptake of foreign DNA from its surroundings
transduction- phages the virus that infect bacteria, carry prokaryotic genes from one host cell to another.
Transduction process-
Conjugation & Plasmids
Conjugation- DNA is transferred between two prokaryotic cells(usually of the same species) that are temporarily joined.
Conjugation process-
F factor- (
Fertility
) the ability to form pili and donate DNA during conjugation results from this presence of a particular piece of DNA.
The F factor as a plasmid: F plasmid- cells containing the F plasmid designated F+ cells, function as DNA donors during conugation.
R plasmids and Antibiotic Resistance: R plasmids- such resistance genes are often carried by plasmids; (R for
R
estance).
27.3
The Role of Oxygen in Metabolism
Obligate aerobes- must use O2 for cellular respiration and cannot grow without it.
Obligate anaerobes- on the other hand, are poisoned by O2.
anaerobic respiration- in which substances other than O2, such as nitrate ions (NO3-) or sulfate ions (SO42-), accept electrons at the "downhill" end of electron transport chains.
Facultative anaerobics- use of O2 if its present but can also carry out fermentation or anaaerobic respiration in an anaerobic environment.
Table 27.1 Major Nutritional Modes
AUTOTROPH
Photoautotroph
Light
CO2, HCO3-, or related compound
Photosynthetic prokaryotes( cyanobacteria), plants; certain protists( algae).
Chemoautotroph
Inorganic chemicals( such as H2, S, NH3, or Fe2+
CO2, HCO3, or related compound
Unique to certain prokaryotes ( Sulfofobus)
HETEROTROPH
Photoheterotroph
Light
Organic compounds
Unique to certain aquatic and salt loving prokaryotes( Rhodobacter, Chloroflexus
Chemoheterotroph
organic compounds
Organic compounds
Many prokaryotes( Clostridium) and prtists; fungi; animals; some other plants
nitrogen fixation- some cyanobacteria and some methanogens (a group of archea) convert atmospheric nitrogen to amonia.
Metabolic Cooperation
heterocysts- (sometimes called hetercytes) carry out only nitrogen fixation
biofilms- metabolic cooperation between different prokaryotic species often occurs in surface-coating colonies
27.4
Table 27.2 A Comparison of the Three Domains of Life
Nuclear envelope
Bacteria- absent
Archaea- absent
Eukarya- present
Membrane enclosed organelles
Bacteria- absent
Archaea- absent
Eukarya- present
Peptidoglycan in cell wall
Bacteria- present
Archaea- absent
Eukarya- absent
Membrane lipids
Bacteria- Unbranched hydrocarbons
Archaea- Some branched hydrocarbons
Eukarya- Unbranched hydrocarbons
RNA polymerase
Bacteria- One kind
Archaea- Several kinds
Eukarya- Several kinds
Initiator amino acid for protein synthesis
Bacteria- Formyl-methionine
Archaea- Methionine
Eukarya- Methionine
Introns in genes
Bacteria- Very rare
Archaea- Present in some genes
Eukarya- Present in many genes
Response to the antibiotics streptomycin and chloramphenicol
Bacteria- Growth usually inhibited
Archaea- Growth not inhibited
Eukarya- Growth not inhibited
Histones associated with DNA
Bacteria- Absent
Archaea- Present in some species
Eukarya- Present
Circular chromosomes
Bacteria- Present
Archaea- Present
Eukarya- absent
Growth at temperatures > 100 C
Bacteria- No
Archaea- Some species
Eukarya- No
Archaea
extremophiles- meaning "lovers" of extreme conditions
Extreme halophiles- live in highly saline enviroments, such as Great Salt Lakein Utah,the Dead Sea.
Extreme thermophiles- thrive in very hot enviroments
methanogens- archaea that release methane as a by-product of their unique ways of obtaining energy.
27.5
Chemical Recycling
decomposers- breaking down dead organisms as well as waste products and thereby unlocking supplies of carbon, nitrogen, and other elements.
Ecological Interactions
symbiosis- and ecological relationship in which two species live in close contact with each other
Host- larger organism in a symbiotic relationship
symbiont- the smaller organism in the relationship
mutualism- an ecological interaction between two species in which both benefit
commenensalism- an ecological relationshipin which one species benefits while the is not harmed or helped in any significant way
parasitism- ecological relationship where a parasite eats the cell contents, tissues, or body fluids of its host
Parasite- eats the cell contents, tissues, or body fluids of the host
Pathogens- parasites that cause disease, many of which are prokaryotic
27.6
Pathogenic Bacteria
exotoxins-are proteins secreted by certain bacteria and other organisms
endotoxins- are lipopolysaccharide components of the outer membrane of gram-negative bacteria
Prokaryotes in Research and Technology
bioremediation- the use of organisms to remove pollutants from soil, air, or water.
