Diversity of Microbial Life: Prokaryotes (Bacteria & Archaea)

Vocabulary flashcards covering the diversity, structure, reproduction, and metabolic categories of prokaryotic life (Archaea and Bacteria) based on Lecture 23.

Microorganisms (microbes)

Organisms that are typically so small that they can only be seen with the use of a microscope, including prokaryotic domains Archaea and Bacteria, and eukaryotic phyla of protists and fungi.

Horizontal gene transfer (HGT)

A process, also known as lateral gene transfer, where an organism receives genetic material from another organism without being the offspring of that organism; it is common among archaea and bacteria.

Binary fission

A rapid form of prokaryotic reproduction where a cell divides into two; it is simpler than mitosis as it involves only one circular chromosome.

Plasmids

Small rings of DNA with supplemental genes that replicate independently of the chromosome and can be transferred from cell to cell.

R plasmids

Specific types of plasmids that carry genes conferring antibiotic resistance to the bacterial cell.

Thaumarchaeota

A phylum of Archaea containing species that oxidize ammonia, playing an important role in global nitrogen cycling.

Euryarchaeota

A phylum of Archaea that includes hyperthermophiles, diverse methane producers, and extreme halophiles.

Asgard archaea

A superphylum of Archaea noted for having a particularly close evolutionary relationship to the Domain Eukarya.

Peptidoglycan

A sugar-polymer cross-linked by polypeptides used in cell walls; it is unique to bacteria and absent in the cell walls of archaea.

Ether bonds

Distinctive bonds found in Archaean membrane lipids that provide resistance to damage by heat and other extreme environmental conditions.

Isoprene chains

The specific type of chains used to build Archaean membranes, as opposed to the fatty acid chains used by bacteria and eukaryotes.

Deinococcus-Thermus

A bacterial phylum known for extremophiles, including the genus Thermus, which is the source of Taq polymerase for PCR.

Cyanobacteria

The only prokaryotes known to generate oxygen as a product of photosynthesis; they contain an internal membrane system called photosynthetic lamellae.

Nitrogen fixation

The process of converting nitrogen into ammonia, performed by certain cyanobacteria in specialized cells called heterocytes.

Akinetes

Large, thick-walled, food-filled cells produced annually by filamentous cyanobacteria to survive winter and germinate in the spring.

Endospores

Heat-resistant, dormant structures produced by some bacteria (such as Clostridium and Bacillus) that can survive unfavorable conditions for up to $1,000$ years.

Alphaproteobacteria

A class of Proteobacteria related to the ancestors of mitochondria, including nitrogen-fixing bacteria and species that consume methane.

Thylakoids

Flattened, tubular membranes growing inward from the plasma membrane in photosynthetic bacteria, associated with chlorophyll.

Magnetosomes

Tiny mineral crystals surrounded by membrane that allow certain bacterial cells to orient themselves in relation to the Earth's magnetic field.

Cocci

Bacterial cells that are shaped like spheres.

Bacilli

Bacterial cells shaped like elongate rods.

Vibrios

Bacterial cells that are comma-shaped.

Spirochaetes

Flexible, spiral-shaped bacterial cells with flagella held close to the body.

Spirilli

Bacterial cells that are rigid and spiral-shaped.

Gram-positive bacteria

Bacteria with a thick peptidoglycan cell wall that retains the blue/purple color of the Gram stain.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer surrounded by a lipid membrane; they do not retain Gram stain and appear red.

Mucilage

A coat of slimy material, also called a capsule or glycocalyx, used by bacteria to evade host defenses and bind to surfaces.

Biofilms

Communities of microbes that bind to solid surfaces and secrete a sticky polysaccharide matrix that traps other cells.

Obligate aerobes

Organisms that require $O_2$ as an electron acceptor in respiration.

Obligate anaerobes

Organisms for which $O_2$ is poisonous and who use nitrate, sulfate, or $CO_2$ as electron acceptors.

Facultative anaerobes

Organisms capable of using both aerobic and anaerobic metabolic pathways.

Photoautotrophs

Organisms that use light as an energy source and carbon dioxide as a carbon source.

Photoheterotrophs

Organisms that use light for energy (to generate ATP) but must take in organic compounds as a source of carbon.

Chemolithoautotrophs

Organisms that use inorganic substances for energy and carbon dioxide as a carbon source.

Chemoheterotrophs

Organisms that must obtain organic molecules for both energy and their carbon source; this includes fungi, archaea, and many bacteria.