Chapter 16: Microbial Life: Prokaryotes and Protists

These flashcards cover the characteristics, types, and ecological roles of prokaryotes (Bacteria and Archaea) and protists as presented in Chapter 16.

Prokaryotes

Diverse and widespread single-celled organisms that generally range from $1-5\,\mu m$ in diameter.

Collective Biomass

The total mass of all prokaryotes, which is at least 10 times that of all eukaryotes.

Pathogens

Bacteria that cause disease.

Cocci

Spherical prokaryotic cells; some occur in chains called streptococci.

Bacilli

Rod-shaped prokaryotes that can be threadlike or filamentous.

Spirilla

Short and rigid spiral-shaped prokaryotes.

Spirochetes

Longer, more flexible spiral-shaped prokaryotic cells.

Cell Wall

A structure in nearly all prokaryotes that provides protection and prevents the cell from bursting in a hypotonic environment.

Gram-positive Bacteria

Bacteria with simpler cell walls containing a large amount of peptidoglycan.

Gram-negative Bacteria

Bacteria with complex cell walls containing less peptidoglycan; these are more likely to cause disease.

Peptidoglycan

A polymer found in the cell walls of bacteria.

Capsule

A sticky layer of polysaccharides or protein that allows prokaryotes to adhere to substrates and shields them from host immune systems.

Flagella

External structures that help prokaryotes move in their environment.

Fimbriae

Also called pili, these hair-like projections enable prokaryotes to stick to surfaces or each other.

Binary Fission

The asexual process by which prokaryote populations grow and rapidly produce new generations.

Plasmids

Small, circular DNA molecules that replicate independently of the main chromosome.

Endospores

Specialized cells that remain dormant through harsh conditions, surviving extreme heat or cold.

Phototrophs

Organisms that capture energy from sunlight.

Chemotrophs

Organisms that harness energy stored in chemicals.

Autotrophs

Organisms that obtain carbon atoms from carbon dioxide ($CO_2$).

Heterotrophs

Organisms that obtain carbon atoms from organic compounds present in other organisms.

Photoautotrophs

Organisms that use sunlight for energy and $CO_2$ for carbon.

Photoheterotrophs

Organisms that obtain energy from sunlight and carbon from organic molecules.

Chemoautotrophs

Organisms that harvest energy from inorganic chemicals and use $CO_2$ for carbon.

Chemoheterotrophs

Organisms that acquire both energy and carbon from organic molecules.

Biofilms

Complex associations of microbes that communicate via chemical signals and form difficult-to-eradicate communities on surfaces.

Bioremediation

The use of organisms to remove pollutants from soil, air, or water.

Domain Archaea

One of two prokaryotic domains; members often live in extreme environments.

Extreme Halophiles

Archaea that thrive in very salty environments.

Extreme Thermophiles

Archaea that thrive in very hot or acidic water.

Methanogens

Archaea that live in anaerobic environments and produce methane as a waste product.

Proteobacteria

A group of gram-negative bacteria that represent all four modes of nutrition; includes species like Rhizobium.

Symbiosis

A close association between organisms of two or more species.

Cyanobacteria

Prokaryotes capable of plantlike, oxygen-generating photosynthesis; sometimes called blue-green algae.

Chlamydias

Bacteria that live inside eukaryotic host cells and are common causes of blindness and STDs.

Exotoxins

Powerful poisonous proteins secreted by bacterial cells into their environment.

Endotoxins

Lipopolysaccharide components of the outer membrane of gram-negative bacteria that cause illness.

Koch’s Postulates

Four essential conditions used to establish that a specific bacterium causes a disease.

Protists

A diverse collection of mostly unicellular eukaryotes that are not plants, animals, or fungi.

Algae

Autotrophic protists that produce food by photosynthesis.

Protozoans

Heterotrophic protists that consume bacteria and other protists.

Mixotrophs

Protists capable of both photosynthesis and heterotrophy.

Endosymbiont Theory

The theory that mitochondria and chloroplasts evolved from prokaryotes living inside larger host cells.

Secondary Endosymbiosis

The process where an autotrophic eukaryotic protist became endosymbiotic within a heterotrophic eukaryotic protist.

Diatoms

Unicellular chromalveolate algae with glass cell walls containing silica.

Dinoflagellates

Unicellular protists that are common components of marine plankton.

Brown Algae

Large, multicellular autotrophic chromalveolates, such as kelp.

Amoebas

Protists that move and feed using pseudopodia.

Pseudopodia

Temporary extensions of the cell used for locomotion and feeding.

Foraminiferans

Rhizarians with porous shells called tests composed of calcium carbonate.

Radiolarians

Mostly marine rhizarians with a mineralized internal skeleton made of silica.

Excavata

A clade of protists with modified mitochondria and often an excavated feeding groove.

Plasmodium

A single, multinucleate mass of cytoplasm found in plasmodial slime molds.

Archaeplastids

A supergroup of eukaryotes including red algae, green algae, and land plants.

Sporophyte

The multicellular diploid ($2n$) form in the alternation of generations life cycle.

Gametophyte

The multicellular haploid ($1n$) form in the alternation of generations life cycle.