chapter 17 bacteria and archaea Flashcards
what are prokaryotes?
single-celled organism that lacks a nucleus and membrane-bounded organelles
are bacteria and archaea prokaryotes?
yes
when did prokaryotes evolve?
4 billion years ago
what is used to distinguish between bacteria and archaea?
DNA sequences and chemical composition
what do bacteria and archaea have in common?
prokaryotic, small, circular chromosome, predominantly unicellular, and some can fix nitrogen or grow at temperatures above 80 degrees C
unique features of bacteria
cell wall typically composed of peptidoglycan, membrane based on fatty acids, some use chlorophyll, cannot generate methane, sensitive to streptomycin, and genes do not contain introns
unique features of archaea
cell wall composed primarily of protein, membrane based on nonfatty acid lipids, do not use chlorophyll, some generate methane, insensitive to streptomycin, and genes may contain introns
do bacteria and archaea have similar internal and external structures?
yes
nucleoid
the region where the DNA resides
ribosomes
use mRNA to synthesize proteins
plasmids
circles of DNA apart from the chromosome
cell membrane
the outer boundary of the cell; it regulates what can enter and exit the cell
cell wall
outside the membrane. gives the cell its shape and protects it from osmotic pressure
glycocalyx
Many (but not all) bacteria and archaea have a layer of proteins or polysaccharides surrounding the cell wall. This layer helps cells attach to surfaces, form biofilms, and evade the immune system
pili
short, hairlike projections made of protein that enable cells to adhere to objects, surfaces, and other cells
what are sex pili used for?
exchanging DNA with other cells
flagella
long, whip-like extensions made of protein that rotate like propellers to help the cells move
taxis
a response that enables cells to move toward or away from external stimuli
gram positive cells have…
a thick peptidoglycan layer
gram negative cell walls consist of…
a thin inner layer of peptidoglycan plus a protective outer membrane of lipid, polysaccharide, and protein
3 most common shapes for bacteria
coccus (spherical), bacillus (rod-shaped), and spirillum (spiral)
endospores
dormant, thick-walled structures that can survive harsh conditions
found in some types of gram-positive bacteria
how are prokaryotes classified?
based on metabolism
photoautotrophs
derive energy from the sun
chemoautotrophs
acquire energy by oxidizing inorganic or organic chemicals
what do aerobic prokaryotes require?
oxygen
obligate aerobes
require oxygen to live
obligate anaerobes
are killed by oxygen, so they only live in habitats that lack it
facultative anaerobes
can live in aerobic or anaerobic environments
vertical gene transfer
aka binary fission
asexual process that replicates DNA and distributes it to two cells
horizontal gene transfer
a cell receives DNA from a cell that is not its ancestor
the three ways horizontal transfer occurs
transformation, transduction, and conjugation
transformation
a dying cell may release its genetic material as it bursts, and other cells absorb stray bits of DNA
transduction
a virus transfers this combined DNA to a bacterial cell
conjugation
one cell receives DNA via direct contact with another cell
sex pilus
the appendage through which DNA passes from donor to recipient
the largest group of gram-negative bacteria
proteobacteria
includes heterotrophic facultative anaerobes that live in our intestines and autotrophs that obtain energy from sulfur
the first cells to release oxygen gas as a byproduct of photosynthesis
cyanobacteria
ancient [blank] gave rise to chloroplasts during endosymbiosis
cyanobacteria
members of this domain were first discovered in extreme habitats
archaea
many archaea are extremophiles
