ch 27 bacteria and archea

what are the most abundant organisms on earth

prokaryotes due to their ability to adapt to diverse habitats

how small are prokaryotes

0.5-5 micrometers

what are the most common shapes of prokaryotes

spheres (cocci), rods (bacilli) and spirals. most infectious pathogenic bacteria are in one of these shapes

cell wall

maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment. contains peptidoglycan

peptidoglycan

a network of sugar polymers cross linked by polypeptides. unlike eukaryotic cell walls that are made of chitin or cellulose. archae has polysaccharides and protiens but lacks peptidoglycan

gram stain

used to classify bacteria by cell wall composition by using crystal violet

gram positive

bacteria has simpler walls with a large amount of peptidoglycan (turns purple)

gram negative

bacteria have less peptidoglycan and an outer membrane that contains lipopolysaccharides (turns pink)

capsule

sticky outer layer of polysaccharide or protein that allows adherence to the substrate or other individuals, shielding pathogenic bacteria from the host immune system

fimbrae

hairlike appendages that some prokaryotes have that allow them to stick to their substrate or other individuals in a colony

pili

longer than fimbrae, allow prokaryotes to exchange DNA. also called sex philli

taxis

the ability to move towards or away from a chemical stimulus. about half of prokaryotes have

positive taxis

ability to move towards

negative taxis

ability to move away

flagella

most common structures used by prokaryotes for movement. may be scattered about the surface or concentrated at one or both ends

how do flagella of prokaryotes and flagella of eukaryotes differ

structure, mechanism or propulsion, and molecular composition

what do prokaryotic cells usually lack

complex compartmentalization so they have specialized membranes that perform metabolic functions

what do the infoldings of the plasma brain of prokaryotic cells do

preform metabolic functions like producing ATP by glycolysis

do prokaryotic genomes have less DNA than the eukaryotic genome

yes. this is because the chromosome is located in the nucleoid region with no surrounding membrane.

what do prokaryotic genomes consist of

circular chromosomes

plasmids

smaller rings of independently replicating DNA (philli exchanges this)

how do prokaryotes reproduce

by binary fission (splitting of one into two during DNA replication) every 1-3 hours

what do many prokaryotes form metabolically

inactive endospores that can remain viable in harsh conditions for centuries in the cell well until conditions are right again

prokaryotic genetic diversity

due to rapid reproduction, mutation, and genetic recombination

why do prokaryotes have low mutation rates

because they produce asexually so they have identical offspring. however this means mutations can accumulate rapidly.

do prokaryotes have simpler cells than eukaryotes

yes but their rapid adaptation to environmental change indicates they are highly evolved

genetic recombination

the combining of DNA from two sources. contributes to diversity

how can prokaryotes take in a plasmid/be brought together

transformation, transduction, and conjugation

transformation

a prokaryotic cell can take up incorporate foreign DNA from the surrounding environment

transduction

movement of genes between bacteria by phages (viruses)

conjugation

genetic material is transferred between prokaryotic cells. donor cell attaches to a recipient by a pilus, pulls it closer, and transfers DNA through a mating bridge

nutrition forms with energy

phototrophs: energy from light

chemotrophs: obtain energy from chemicals

nutrition forms with carbon

autotrophs: need CO2 or related compounds as a carbon source

heterotrophs: need an organic nutrient to make organic compounds

which nutrition forms are in eukaryotic cells

photoautotrophs and chemoheterotrophs

obligate aerobes

require O2 for cellular respiration

obligate anaerobes

poisoined by O2 and live by fermentation or use substances other than O2 for anaerobic respiration

facilitative anaerobes

can use O2 if it is present or carry out fermentation or anaerobic respiration if it is not

what role do prokaryotes play in the biosphere

recycle chemical elements betwen the living and nonliving components of the environment and convert molecules to forms that can be taken up by other organisms

how do prokaryotes convert molecules

they increase the availability of nutrients required for plant growth such as nitrogen

what prokaryotes function as decomposers

chemoheterotrophs

what ecological interactions do prokaryotes have

they form symbiotic relationships with larger organisms

symbiosis

ecological relationship in which two species live in close contact as a large host and small symbiont

mutualism

both organisms benefit

commensalism

one benefits while neither harming or helping the other

parasitism

an organism harms but does not kill the host

what good impacts do prokaryotes have on humans

mutualistic, bacteria in human intestines help break down food that is digested by our intestines

what bad impacts do prokaryotes have on humans

pathogenic, bacteria causes half of human diseases. often transmitted through vectors (ticks, etc)

genetic analysis led to

the division of prokaryotes into two domains

what are the 5 major bacteria

protobacteria, chlamydias, spirochetes, cyanobacteria, and gram positive bacteria

proteobacteria

gram negative bacteria that includes photoautotrophs, chemoautotrophs, and heterotrophs. some aerobic and some anaerobic. greek letters

chlamydias

parasites that live within animal cells

spirochetes

helical gram negative. some parasites

cyanobacteria

gram negative photoautotrophs that generate O2. chloroplasts evolved from these by endosymbiosis. abundant components of freshwater and marine phytoplankton

gram positive

colony forming groups such as actinomycetes. many help decompose organic matter. solitary species include pathogenic species

archaea

share certain traits with bacteria (size and shape) and eukaryotes (genes, metabolic pathways)

extreme halophiles

live in highly saline environments

extreme thermophiles

live in very hot environments

methanogens

live in swaps/marshes and produce methane as waste. strict anaerobes and poisoined by O2