Chapter 27: Bacteria and Archaea

Flashcards from Chapter 27 of Pearson's Campbell Biology, Twelfth Edition.

Prokaryotes

Single-celled organisms in the domains Bacteria and Archaea

• Were the first to inhabit Earth

• Are typically between 0.5 to 5 micrometers in size

• Can form colonies

• Shapes include spheres, rods, and spirals

Size or prokaryotes

0.5 to 5 um

Colonies

Groups of single-celled organisms that all help sustain the body

• Have been seen forming in prokaryotes

Cocci

Spherically-shaped prokaroytes

Bacilli

Rod-shaped prokaryotes

Spirals

Spiral-shaped prokaryotes

Cell wall

Structure on cells of prokaryotes that:

• Maintains shape

• Protects the cell

• Prevents bursting in hypotonic environemnts

Made of cellulose or chitin in eukaryotes and peptidoglycan in bacteria

Plasmolysis

The loss of water in prokaryotes in a hypertonic (high solute) environment, as water rushes out of the cell

• Taken advantage of through using salt as a preservative

Hypertonic solution

A solution that has high levels of solute and thus causes cells to shrink

Hypotonic solution

A solution that has low levels of solute and thus causes cells to swell

Peptidoglycan

The substance miost bacterial cell walls are made out of

• Archaeal cells lack this, though they do have a variety of polysaccharides and proteins

• Not found in human cells, enabling antibiotics that target bacteria

Gram stain

A classification system for bacteria based on cell wall composition, dividing into

• Gram-positive (simpler) bacteria with a thick layer of peptidoglycan

• Gram-negative (complex) bacteria with a thin layer of peptidoglycan and an outer layer containing lipopolysaccharides

Gram-positive bacteria

Bacteria with simpler walls and a large amount of peptidoglycan

• More vulnerable to antibiotics due to them targeting peptidoglycan

Gram-negative bacteria

Bacteira with less peptidoglycan and more complex walls containing lipopolysaccharides

• Stains purple

• More resistant to antibiotics due to them targeting peptidoglycan

Capsule

A dense, well-defined sticky outer layer of polysaccharides or proteins surrounding the prokaryotic cell wall

Slime layer

A loose, unorganized sticky outer layer of polysaccharides or proteins surrounding the prokaryotic cell wall

Endospores

Metabolically inactive survival structures when conditions are unfavorable; can remain viable for centuries

Fimbriae

Hair-like appendages prokaryotes use for attachment to substrates or other individuals in a colony

Pili

Longer appendages prokaryotes use to pull cells together to enable the exchange of DNA

Taxis

The ability to move toward or away from a stimulus

Chemotaxis

Movement (taxis) in response to chemicals

Flagella

The most common structures used by prokaryotes for movement, with three main parts:

• The filament, or the tail of the flagella and most visible part

• The hook, or the base of the outer flagella

• The motor, which rotates the hook and is contained mostly under the cell wall

Nucleoid

A region without a membrane that contains the chromosome in prokaryotes

Plasmids

Small, independently replicating rings of DNA

Binary fission

The method by which prokaryotes reproduce, typically taking one to three hours under optimal conditions

Genetic diversity factors

Includes:

• Rapid reproduction

• Mutation

• Genetic recombination

Genetic recombination

The combination of DNA from two sources, increasing prokaryote diversity

Horizontal gene transfer

The movement of genes between individual species of prokaryotes

• Enables genes to evolve and adapt

Transformation

The uptake of foreign DNA from the environment, which can enable new traits

Transduction

DNA transfer from bacteriophages which can carry prokaryotic genes from one host cells to another

Conjugation

The process of direct DNA transfers between prokaryotes; one cell donates and the other receives

F factor

A piece of DNA required for the production of pili

• Can exist as a plasmid or segment of DNA

F+ cells

Cells that contain the F plasmid and function as donors

F- cells

Cells that lack the F plasmid and function as recipients

High frequency recombination cells (Hfr cells)

Cells with the F factor integrated into the chromosome that function as donors during conjugation

R plasmids

Plasmids that contain antibiotic resistance genes

Phototrophs

Organisms that obtain energy from light

Chemotrophs

Organisms that obtain energy from chemicals

Autotrophs

Organisms that use CO₂ or related compounds as a carbon source

Heterotrophs

Organisms that require organic nutrient compounds for energy

Modes of nutrition

Includes:

• Photoautotrophs (self-producing with light)

• Chemoautotrophs (self-producing with chemicals)

• Photoheterotrophs (requires nutrients with light)

• Chemoheterotrophs (requires nutrients with other chemicals)

Obligate aerobes

Prokaryotes that require O₂ for cellular respiration

Obligate anaerobes

Prokaryotes that are poisoned by O₂ and live by fermentatio or other substances for anaerobic respriation

Facultative anaerobes

Prokaryotes that can survive with or without oxygen

Nitrogen fixation

The conversion of atmospheric nitrogen to ammonia for nutrients

Heterocysts

Specialized nitrogen-fixing cells in cyanobacteria

Biofilms

Surface-coating colonies of prokaryotes; these can cause

• Tooth decay

• Chronic, antibiotic-resistant functions

• Medical device contamination

Prokaryotic domains

Includes Bacteria and Archaea

Cyanobacteria

Photosynthetic bacteria that gave rise to chloroplasts and photosynthesis

Spirochetes

Helical bacteria that rotate internal filaments and spiral through their environment

Extremophiles

Archaea that live in extreme environments, uninhabitable for most organisms

• Seen in highly saline or hot environments

• Does not include Bacteria

Methanogens

Obligate anaerobes that produce methane as a by-product of their metabolism

Metagenomics

The testing of soil to find several different species of prokaryotes

• Contributes to growing understandings of bacteria

Proteobacteria

Gram-negative bacteria that is hard to kill

• Has some heterotrophs that are pathogenic

• Chamydias are parasitic

Decomposers

Organisms that break down dead organisms and wastes, releasing carbon

• Prokaryotes are essential for this

Symbiosis

A close ecological relationship between species, has types:

• Mutualism (both benefit)

• Commensalism (one benefits, other unaffected)

• Parasitism (one harms the other)

Mutualism

Type of symbiosis where one organism benefits

Commensalism

Type of symbiosis where one organism benefits and the other is unaffected

Parasitism

Type of symbiosis where one organisms harms the other

Pathogens

Parasites that can cause disease

• Represent a small fraction of prokaryotes

Exotoxins

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

Endotoxins

Lipopolysaccharide components of gram-negative bacteria on their outer membrane, only released when bacteria die and cell walls break down

CRISPR-Cas9 system

A gene editing system derived from prokaryotes

Bioremediation

The use of organisms to remove pollutants, as is seen with some plastic-eating bacteria