BY 124- Gibbons Ch 27- Bacteria and Archaea

What is a key difference between Prokaryotes and Eukaryotes?

A. Eukaryotes are smaller than Prokaryotes

B. Prokaryotes have membrane bound organelles and Eukaryotes do not

C. Prokaryotes have circular chromosomes and Eukaryotes have linear chromosomes

D. Prokaryotes have a nucleus and Eukaryotes have a nucleoid

C. Prokaryotes have circular chromosomes and Eukaryotes have linear chromosomes

Prokaryote Characteristics

Prokaryote characteristics:

• Single celled

• Smaller than eukaryotes

• Variety of shapes

  • Cocci (circular)

  • Bacilli (rod-shaped)

  • Spiral

• Can achieve all of life’s functions in a single cell

Prokaryote Cell Wall

• In Bacteria, cell walls contain peptidoglycan

• In Archaea, cell walls have no peptidoglycan

Eukaryote Cell Wall

• Fungi cell walls are made of chitin

• Plant cell walls made of cellulose

Gram-positive vs Gram-negative

• Gram-positive: simple cell wall structure, thick layer of

  peptidoglycan

• Gram-negative: less peptidoglycan, more complex with

  an outer membrane

• Actions of antibiotics are different for gram-positive and –negative bacteria (gram negative are usually more resistant)

• Antibiotics usually affect peptidoglycan, so don’t impact

  human cells

Prokaryote Capsules and Endospores

Capsule/slime layer

• outer layer allowing adherence to substrate or other bacteria

Endospore:

• Chromosomes copied and surrounded by protective structure

• Formed when bacteria become inactive in sparse conditions

• Withstands extreme conditions

Prokaryote Fimbriae and Sex Pili

Fimbriae:

• hairlike appendages

• allow them to stick to their substrate/other individuals

• Pili (or sex pili):

• longer than fimbriae

• pull cells together for exchange of DNA

Prokaryote Motility and Movement

• Taxis: the ability to move toward or away from a stimulus

• Flagella: structure used by prokaryotes for movement.

Prokaryote Internal Organization

• Simple structure, no membrane-bound organelles

• Smaller genome (less DNA) than eukaryotes

• One circular chromosome; eukaryotes have multiple linear chromosomes

• Lack a nucleus; the chromosome is in the nucleoid

• May have plasmids: small rings of DNA

• Differences in DNA replication, transcription and translation from Eukaryotes

  • Allow antibiotics to kill or inhibit bacterial cell growth without harming human cells

Prokaryote Reproduction

• Binary fission (as fast as every 1–3 hours!!)

• There are three key features of rapid prokaryote reproduction:

  • They are small

  • They reproduce by binary fission

  • They have short generation times

Genetic Diversity in Prokaryotes

• Prokaryotes are incredibly diverse in forms and adaptations

• Three factors are responsible

  • Rapid reproduction

  • Mutation

  • Genetic recombination

Prokaryote Reproduction and Mutation

• Variations arise through mutation

• Mutation rates are low, but can accumulate quickly in large populations with rapid reproduction

• Leads to natural selection/adaptation in challenging environments

Prokaryote Genetic Recombination

• Genetic Recombination: combining of DNA from 2 sources

  • Transformation

  • Transduction

  • Conjugation

  • Horizontal gene transfer

Prokaryote Genetic Recombination - Transformation

Incorporation of foreign DNA

Prokaryote Genetic Recombination - Transduction

Viruses carry genes from one host cell to another

Prokaryote Genetic Recombination - Conjugation

• Conjugation: DNA is transferred between two prokaryotic cells

• E. coli steps:

  • pilus of the donor cell attaches to the recipient

  • pilus retracts

  • DNA is transferred through a temporary structure called the “mating bridge”

Which of the following forms of genetic recombination in Prokaryotes involves viruses?

A. Transformation

B. Transduction

C. Conjugation

D. Binary Fission

Transduction

Prokaryote Genetic Recombination - Horizontal Gene Transfer

• movement of genes from one organism to another (different species)

• can occur through transformation, transduction, or conjugation

• can spread genes associated with virulence to normally harmless bacteria (E. coli)

Nutritional Modes of Prokaryotes

• Photoautotroph: Light as energy source, photosynthesis (uses CO2)

• Chemoautotroph: Inorganic chemicals as energy source (e.g., H2S), uses CO2

  • Thermal vents!

• Photoheterotroph: Light as energy source, but takes in organic compounds through “eating” for Carbon source

• Chemoheterotroph: Organic compounds for energy and source of Carbon

  • Most bacteria are in this category

Diversity of Prokaryotes: Archaea versus Bacteria

• The use of ribosomal RNA as a marker for relationships (1970s)

• Some “bacteria” were more closely related to eukaryotes than others (now categorized as Domain Archaea)

• Horizontal gene transfer has played a large role in bacterial diversity!

• Most genes in bacterial genomes (75-80%) have been transferred horizontally at some point

Which Domain is more closely related to Eukaryotes?

A. Bacteria

B. Archaea

B. Archaea

Extremophile Archaea

• Many Archaea inhabit extreme conditions unsuitable for other

  species

• Extreme halophiles- occupy environments (lakes) with very high amounts of salt

• Extreme thermophiles- occupy environments with very high temperatures

Ecological Roles of Prokaryotes include:

• decomposers

• symbiosis

• host or parasite

• mutualism

• commensalism

• parasitism

• pathogens

Beneficial Prokaryotes

• Mutualistic Bacteria in the gut: up to 1000 species of bacteria

  • Help us digest food

  • Synthesize vitamins and carbohydrates, etc

  • Involved in signaling absorption of nutrients from small intestine

  • We have 10x more bacteria than human cells in our body!

Harmful Prokaryotes

• Pathogenic Bacteria release endotoxins, causing:

  • Tuberculosis (lung disease)

  • Lyme disease (tick-borne)

  • Cholera (digestive)

  • Botulism, Salmonella, Typhoid fever, etc.

Ability of Prokaryotes to rapidly evolve, especially in challenging environments, has led to _________ ________ by many bacteria

antibiotic resistance

Choose the list below that contains the substances required by typical nitrogen-fixing cyanobacteria.

• Carbon, nitrogen, light, water, and some minerals

• Oxygen, sulfur, light, water, and some minerals

• Carbon dioxide, sulfur, light, water, and some minerals

• Carbon dioxide, ammonium, water, light, and some minerals

• Carbon dioxide, nitrogen, water, light, and some minerals

Carbon dioxide, nitrogen, water, light, and some minerals

Portions of the genomes of certain prokaryotic species are very similar to portions of the genomes of distantly related prokaryotes. The process that most likely accounts for this genetic similarity is __________.

• convergent evolution

• identical mutations occurring independently in these distantly related lineages

• genetic variation arising from binary fission

• genetic variation arising from meiosis

• horizontal gene transfer

Horizontal gene transfer

What is the structural feature of gram-positive bacteria that results in their retaining a crystal violet dye stain and thereby being distinguished from gram-negative bacteria in a Gram-stain technique?

• Gram-positive bacteria have thicker cell walls.

• Gram-positive bacteria have structurally more complex cell walls.

• Gram-positive bacteria lack cell walls.

• Gram-positive bacteria have additional outer membranes.

• Gram-positive bacteria lack peptidoglycan in their cell walls.

Gram-positive bacteria have thicker cell walls.

Which subgroup of proteobacteria contains many species that are closely associated with eukaryotic hosts in mutualistic or parasitic relationships?

• Gamma

• Alpha

• Epsilon

• Beta

• Delta

Alpha

Which of the following characteristics is a reason why a Gram-stain to distinguish gram-positive from gram-negative bacteria is an important tool in a medical diagnosis of a bacterial infection?

• The outer membrane of a gram-negative bacterium helps protect it from the body’s defenses.

• None of the listed characteristics is a reason why a Gram-stain is important in medicine.

• Certain gram-positive bacteria are resistant to antibiotics.

• All of the listed characteristics are reasons why a Gram-stain is important in medicine.

• The cell walls of many gram-negative bacteria are toxic.

All of the listed characteristics are reasons why a Gram-stain is important in medicine.

Bacterial flagella have a very complex structure composed of 42 distinct proteins. What is the most likely explanation for the evolution of these complex structures?

• Exaptation

• Endosymbiosis

• Early bacterial species needed to be able to locomote and thus developed complex flagella to facilitate this motility

• They evolved from earlier, simpler organisms

• Flagella evolved as extensions of other bacterial appendages such as pili and fimbriae

Exaptation

Which of the following statements about cyanobacteria is true?

• It can be said that nitrogen-fixing cyanobacteria are the most self-sufficient of all organisms.

• All of the listed responses are correct.

• Some species may carry on nitrogen fixation.

• They are the only prokaryotes that perform plantlike, oxygenic photosynthesis.

• Some are single cells, whereas others live in filamentous colonies.

All of the listed responses are correct.

Which of the following is a structure that bacteria, archaea, and eukaryotes have?

• Plasma membrane

• Membrane-enclosed organelles

• Nuclear envelope

• Circular chromosome

• Peptidoglycan cell wall
  

Plasma membrane

Which of the following mechanisms is/are (a) means of genetic recombination in prokaryotes?

• Transduction

• None of the listed mechanisms is a means of genetic recombination.

• Transformation

• All of the listed mechanisms are means of genetic recombination.

• Conjugation

All of the listed mechanisms are means of genetic recombination.

Antibiotics administered in human medicine work against bacterial infections by __________.

• providing resources to lure bacteria away from human cells

• interfering with an aspect of bacterial metabolism or structure that differs from that of eukaryotic cells

• raising the host’s body temperature to make a less favorable environment for bacteria

• stimulating the host’s immune system to mount defenses against the bacteria

• preventing any cells from dividing
  

Interfering with an aspect of bacterial metabolism or structure that differs from that of eukaryotic cells

What are biofilms?

• A biofilm is a location where nitrogen has been made available in the environment by bacterial decomposition.

• Biofilms are any resource upon which bacterial colonies can grow.

• A biofilm is the sticky layer surrounding a bacterial cell wall.

• Biofilms are an antibacterial treatment.

• Biofilms are cooperative colonies of bacteria.

Biofilms are cooperative colonies of bacteria.

In an experiment, a microbiologist put equal numbers of each of the following organisms into a flask of sterile broth, consisting mostly of sugar and a few amino acids. She then placed the flask in the dark.

Which of the following organisms would be most likely to survive?

• Chemoheterotrophic bacteria

• Photoautotrophs

• Thermoacidophilic bacteria

• Photoheterotrophs

• Cyanobacteria

Chemoheterotrophic bacteria

What is a difference between the cell walls of prokaryotes and the cell walls of eukaryotes?

• The cell walls of prokaryotes are made of molecules different from those comprising the cell walls of eukaryotes.

• There are no cell walls in eukaryotes.

• The cell walls of prokaryotes do not play a role in structural support.

• Differences in prokaryotic cell wall composition are difficult to discern in the laboratory.

• The cell walls of prokaryotes do not resist osmotic pressure.
  

The cell walls of prokaryotes are made of molecules different from those comprising the cell walls of eukaryotes.

The Desulfovibrio bacterium breaks down organic matter (which it must have) and uses sulfate (not oxygen) as an electron acceptor. As a result, it produces hydrogen sulfide (H₂S), accounting for the "rotten egg" smell of swamp muck. Oxygen is a deadly poison to Desulfovibrio.

We would call Desulfovibrio a(n) __________.

• obligately anaerobic chemoautotroph

• There is insufficient information to answer this question.

• facultatively aerobic chemoheterotroph

• obligately anaerobic chemoheterotroph

• facultatively anaerobic chemoautotroph

Obligately anaerobic chemoheterotroph

Plasmids __________.

• All of the listed responses are correct.

• are transferred from one bacterium to another by conjugation

• allow bacteria to survive adverse conditions

• replicate independently of the main chromosome

• often contain antibiotic resistance genes

All of the listed responses are correct.

What is the function of a bacterial endospore?

• To facilitate persistence in temporarily harsh environments

• To store the genetic material of the cell

• To adhere to a substrate or other bacteria

• To fix nitrogen

• To transfer DNA from one cell to another

To facilitate persistence in temporarily harsh environments

Which of the following does not contribute to bacteria’s ability to evolve rapidly?

• Large populations

• Genetic recombination

• Short generation times

• Sexual reproduction

• Mutation

Sexual reproduction

Why is salt a good preservative to use for foods such as pork and fish?

• Salt is a toxin to prokaryotic cells and leads to their death.

• Salt breaks down the chitin contained in the cell walls of prokaryotes.

• Salt breaks down the peptidoglycan found in the capsule of prokaryotes.

• Prokaryotes living in the food products will take in excess water and explode.

• Prokaryotic cells living in the food will shrink from their cell walls, impacting their ability to reproduce.
  

Prokaryotic cells living in the food will shrink from their cell walls, impacting their ability to reproduce.

Bacteria that __________ tend to have abundant internal membranes.

• are pathogenic

• are gram-negative

• All of the listed responses are correct.

• are photosynthetic

• have flagella

are photosynthetic

Which of the following is not a true statement concerning bacterial flagella?

• Bacterial flagella originate in and extend from the cell wall and plasma membrane.

• There can be more than one flagellum on each bacterial cell.

• Bacterial flagella enable bacteria to move.

• Bacterial flagella are not covered by the plasma membrane as eukaryotic cells are.

• Bacterial flagella are homologous to the flagella of eukaryotic cells.

Bacterial flagella are homologous to the flagella of eukaryotic cells.

Which of the following is not one of the most common prokaryotic cell shapes?

• Spherical

• Spiral

• Cuboidal

• Rod-shaped

• All of the listed cell shapes are very common.

Cuboidal

Some prokaryotes stick to their substrate or to one another by means of hairlike appendages, each called a __________.

• capsule

• heterocyst

• nucleoid

• fimbria

• pilus

fimbria

Acquiring an R plasmid would allow a bacterium to do what?

• Reproduce

• Resist high temperatures

• Conjugate

• Reduce its metabolic rate

• Resist antibiotics
  

Resist antibiotics

Bacteria function primarily in which ecological role?

• Commensalism

• Bacteria are common in all of the listed ecological roles.

• Parasitism

• Mutualism

• Decomposition

Bacteria are common in all of the listed ecological roles.

Bacteria that use light for their energy source and CO₂ for their Carbon source are called __________.

• photoautotrophs

• photochemoheterotrophs

• chemoautotrophs

• photoheterotrophs

• chemoheterotrophs

photoautotrophs

An F⁺ bacterial cell __________.

• has many antibiotic resistance genes

• uses fimbriae to transfer DNA

• acts as a donor during conjugation

• acts as a receptor during conjugation

• transfers DNA by way of transduction

acts as a donor during conjugation

Which of the following is a disease caused by bacteria?

• Smallpox

• Measles

• Tuberculosis

• Common cold

• Aids

Tuberculosis

Which subgroup of proteobacteria contains many species that are predators of other bacteria?

• Delta

• Beta

• Alpha

• Gamma

• Epsilon

Delta

Which group of bacteria is unusual in that they lack peptidoglycan in their cell walls?

• Cyanobacteria

• Gram-negative bacteria

• Chlamydias

• Epsilon proteobacteria

• Spirochetes

Chlamydias

Prokaryotes found inhabiting the Great Salt Lake would be __________.

• extreme halophiles

• extreme thermophiles

• methanogens

• extremophiles

• cyanobacteria

Extreme halophiles