Ch. 27 Bacteria and Archaea

prokaryotes, 3.5 billion years

Were eukaryotes or prokaryotes the first to arise on the planet? How long ago?

Prokaryotes

Singe-celled organisms without compartments that make up domains Bacteria and Archaea

Yes

Did prokaryotes adapt to diverse and extreme environments?

Prokaryotes

What is the most abundant group of organisms on earth?

Cellulose

What makes up eukaryotic cell walls in humans?

Chitin

What makes up eukaryotic cell walls in fungi?

Peptidoglycan

Network of sugar polymers cross-linked by polypeptides that is in most bacterial cell walls

polysaccharides, proteins, peptidoglycan

Archaeal walls contain ____ and ____, but lack ____

Gram-positive

Type of bacteria with simpler walls with a large amount of peptidoglycan

Gram-negative

Type of bacteria that has less peptidoglycan and are more complex with an outer membrane that contains lipopolysaccharides

purple, pink

Gram positive bacteria stains ____ and gram-negative bacteria stains ____

Gram-negative; antibiotics target peptidoglycan

Is gram-positive or gram-negative bacteria more resistant to antibiotics? Why?

They lack peptidoglycan

Why are human cells unaffected by antibiotics?

Capsule

Sticky layer of polysaccharide or protein surrounding the cell wall that is present in many prokaryotes (dense and well-defined)

Slime layer

Sticky layer/coat of polysaccharide or protein surrounding the cell wall that is present in many prokaryotes (not well organized)

adherence, dehydration, immune system

Capsule and/or slime layer enable ____ to the substrate or other individuals, prevent ____, and protect the cell from the host’s ____ ____

Endospores

Formed by bacteria when water or nutrients are lacking; contains a dormant version of the bacteria including its genetic material and surrounds it with a multilayered structure in case in the bacteria disintegrates in extreme conditions

Fimbriae

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

Pili

Longer than fimbriae and function to pull cells togeether enabling the exchange of DNA

Taxis

The ability to move toward or away from a stimulus

half

About ____ of prokaryotes exhibit taxis

Flagella

The most common structures used by prokaryotes for movement

motor, hook, filament

Bacterial flagella are composed of 42 different kinds of proteins that form a ____, ____, and ____

Half

____ of the flagellum’s proteins are essential

Flagella

What structure likely evolved as existing proteins and was added to an ancestral secretory system?

Exaptation

Structures adapted for one function take on new functions through descent with modification

No

Do prokaryotic cells have complex compartmentalization?

less, fewer

Prokaryotes have ____ DNA and produce ____ proteins than the eukaryotes

one, multiple

Prokaryotes have ____ circular chromosome(s) while eukaryotes have ____ linear chromosome(s)

Nucleoid

Region with no membrane where chromosome is kept since prokaryotes lack a nucleus

Plasmids

Smaller rings of independently replicating DNA that prokaryotes may have

rapid reproduction, mutation, genetic recombination

Name the three factors that contribute to high levels of genetic diversity in prokaryote populations

binary fission

Prokaryotes reproduce quickly by ____ ____ and can divide very 1 to 3 hours under optimal conditions

Short

Do prokaryotes have long or short generation times?

identical

Cells produced by binary fission are generally ____, but differences can arise through mutation

low

In terms of binary fission, mutation rates are typically ____, but mutations accumulate with short generation times and large populations

Genetic recombination

The combining of DNA from two sources, contributing to prokaryote diversity

Horizontal gene transfer

Movement of genes between individual prokaryotes of different species

Transformation

Prokaryotic cells incorporate foreign DNA taken up from their surroundings

Transduction

Phages carry prokaryotic genes from one host cell to another

Phages

Viruses that infect bacteria

Transduction

____ is generally an unintended result of the phage replicative cycle

Conjugation

Process through which DNA is transferred between two prokaryotic cells

two

In bacteria, the DNA transfer is always a ____ way process

F factor

Piece of DNA required for the production of pili; can exist either as a plasmid or a segment of DNA within the bacterial chromosome

R plasmids

Plasmids that carry resistance genes and can’t be killed by antibiotics

pili, resistance

R plasmids have genes that encode the ____ used to transfer DNA between cells, enabling the rapid spread of ____

Phototrophs

Organisms that obtain energy from light

Chemotrophs

Organisms that obtain energy from chemicals

Autotrophs

Organisms that require CO2 or related compounds as a carbon source

Heterotrophs

Organisms that require an organic nutrient to make other organic compounds

Photoautotrophs

Organisms that use light as their energy source and CO2, HCO3-, or related compounds as their carbon source

Chemoautotrophs

Organisms that use inorganic chemicals as their energy source and CO2, HCO3-, or related compounds as their carbon source

Photoheterotroph

Organisms that use light as their energy source and organic compounds as their carbon source

Chemoheterotrophs

Organisms that use organic compounds as their energy source and carbon source

Obligate aerobes

Organisms that require O2 for cellular respiration

Obligate anaerobes

Organisms that are poisoned by O2 and live by fermentation or use substances other than O2 for anaerobic respiration

Facultative anaerobes

Organisms that use O2 if it’s present or carry out fermentation or anaerobic respiration if not

Nitrogen

Gas that is essential for the production of amino acids and nucleic acids in all organisms

Nitrogen fixation

Process by which some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3)

Hetercysts

Cells that isolate nitrogen fixation and prevent oxygen penetration

carbohydrates, heterocysts

Photosynthetic cells exchange ____ for the fixed nitrogen produced by the ____

Biofilms

Surface-coating colonies that are formed by cells of one or more prokaryote species; cells near the edge release signaling molecules to recruit new cells

nutrients, wastes

Channels in the biofilm allow ____ to reach cells in the interior and ____ to be expelled

common

Are biofilms common or uncommon in nature?

proteins, polysaccharides

Biofilm cells secrete sticky ____ and ____

Yes

Do prokaryotes inhabit every environment known to support life?

other species

Significant portions of the genomes of prokaryotes are mosaics of genes imported from ____ ____

Proteobacteria

Phyla of gram-negative bacteria

Chlamydias

Species that parasitize animal cells and have gram-negative walls lacking peptidoglycan

Spirochetes

Bacteria that are helical gram-negative heterotrophs that spiral through the environment by rotating internal filaments; many are free-living, but others are pathogens

Cyanobacteria

Gram-negative photoautotrophs; solitary and filamentous types are abundant components of freshwater and marine phytoplankton

cyanobacteria

Plant chloroplasts likely evolved from ____ by the process of endosymbiosis

Extremophiles

Archaea that live in extreme environments, uninhabitable for most organisms

Extreme halophiles

Organisms that either tolerate or require highly saline environments

Extreme thermophiles

Organisms that have adaptations that make their DNA and proteins stable at high temperatures (even above 100 degrees Celsius)

Methanogens

Obligate anaerobes that are found in diverse environments and produce methane as a by-product of their metabolism

Euryarchaeota

Clade that includes many of the extreme halophiles, most methanogens, and some extreme thermophiles

Prokaryotes

____ play a major role in the recycling of chemical elements between the living and nonliving components of the environment

Decomposers

Organisms that break down dead organisms and wastes and release carbon and other elements

Symbiosis

Ecological relationship in which two species live in close contact: a larger host with a smaller symbiont

Mutualism

Relationship where both symbiotic organisms benefit

Commensalism

Relationship where one organism benefits while neither harming nor helping the other

Parasitism

Relationship where an organism called a parasite harms but does not usually kill its host

Pathogens

Parasites that cause disease

chemoautotrophic

Ecological communities of hydrothermal vents depend on ____ bacteria for energy

pathogens

The best-known prokaryotes are human ____, but they represent a small fraction of prokaryotes

Yes

Do intestinal bacterial cells collectively outnumber all human cells in the body by a factor of ten?

mutualists

Many intestinal bacteria are ____

bacteria

All known pathogenic prokaryotes are ____

Bacteria

____ causes about half of all human diseases

Exotoxins

Proteins secreted by bacteria that can cause disease even if the bacteria are no longer present

Endotoxins

Lipopolysaccharide components of the outer membrane of gram-negative bacteria

dies, breaks down

Endotoxins and exotoxins are only released when bacteria ____ and its cell walls ____ ____

Horizontal gene transfer

____ ____ ____ can spread genes associated with virulence to normally harmless bacteria

At least 1

For every antibiotic now in use, how many species of bacteria have developed resistance to it?

Rapid reproduction

____ ____ enables bacterial cells carrying resistance genes to quickly produce large numbers of resistant offspring

Horizontal gene transfer

Resistance genes spread rapidly within and among bacterial species by ____ ____ ____

CRISPR

System that has been developed as a gene altering tool and also helps prokaryotes defend against viral attack

thermophiles

If a scientist is researching how to improve PCR by studying the source used in each step of the reaction, they will probably need a culture of extreme ____