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peptidoglycan
- network of modified sugar polymers ross linked by short polypeptides
- encloses the entire bacterium and anchors other molecules that extend from its surface
lacking in archaeal cell walls
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gram stain
used to classify many bacterial species into two groups based on cell wall composition
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gram-positive
bacteria have simpler walls with large amount of peptidoglycan
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gram-negative
less peptidoglycan and structurally more complex with an outer membrane that contains lipopolysaccharides
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capsule
- sticky layer of polysaccharide or protein
- enables prokaryotes to adhere to their substrate or to other individuals in a colony
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fimbriae
hairlike protein appendages that help prokaryotes stick to their substrate or to one another
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nucleoid
region of cytoplasm that appears lighter than the surrounding cytoplasm
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plasmids
smaller rings of separately replicating DNA
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endospores
- resistant cells produced when essential nutrient is lacking
- the original cell produces a copy of its chromosome and surrounds it with a tough wall
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transformation
genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings
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transduction
- bacteriophages carry bacterial genes from one host cell to another
- a type of horizontal gene transfer
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conjugation
genetic material is transferred between two bacterial cells that are temporarily joined
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f factor
- consists of about 25 genes
- can exist either as aplasmid or as a segment of DNA within a bacterial chromosome
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r plasmids
resistance genes carried by plasmids
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photoautotrophs
photosynthetic organisms that capture light energy and use it to drive the synthesis of organic compounds from COs or other inorganic carbon compounds
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chemoautotrophs
need only as inorganic compound such as CO2 as a carbon source
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photoheterotrophs
harness energy from light but must obtain carbon in organic form
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chemoheterotrophs
must consume organic molecules to obtain both energy and carbon
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obligate aerobes
use O2 for cellular respiration and cannot grow without it
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obligate anaerobes
- are poisoned by O2
- some live by fermentation
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anaerobic respiration
nitrate ions or sulfate ions accept electrons at the downhill end of electron transport chains
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facultative anaerobes
use O2 if it is present but can also carry out anaerobic environment
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nitrogen fixation
convert atmospheric nitrogen to ammonia
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heterocytes
carry out only nitrogen fixation
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biofilms
surface-coating colonies in which metabolic cooperation between different prokaryotic species occurs
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extremophiles
"lovers" of extreme conditions
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extreme halophiles
live in highly saline environments
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extreme thermophiles
thrive in very hot environments
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methanogens
use CO2 to oxidize H2 releasing methane as a waste product
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decomposers
- breaking down corpses, dead vegetation and waste products
- unlocking supplies of carbon, nitrogen, and other elemnts
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symbiosis
an ecological relationship in which two species live in close contact with one another
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commensalism
one species benefits while the other is not harmed or helped in any significant way
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parasitism
a parasite eats the cells contents, tissues, or body fluids of its host
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exotoxins
proteins secreted by certain bacteria and other organisms
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endotoxins
lipopolysaccharide components of the outer membrane of gram-negative bacteria
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