Campbell Biology Chapter 27: Bacteria and Archaea Vocabulary

Vocabulary flashcards covering prokaryotic structure, genetics, nutrition, respiration, and classification from Campbell Biology Chapter 27.

Gram-Positive Bacteria

Bacteria with simpler cell walls that contain a large amount of peptidoglycan.

Gram-Negative Bacteria

Bacteria with complex cell walls containing less peptidoglycan and an outer membrane composed of lipopolysaccharides.

Cocci

Spherical-shaped prokaryotic cells.

Bacilli

Rod-shaped prokaryotic cells.

Spirilli

Helical-shaped prokaryotic cells.

Capsule

A sticky protective layer secreted outside the cell wall by many prokaryotes that allows them to adhere to surfaces or each other.

Fimbriae

Surface appendages (also known as attachment pili) used by prokaryotes to adhere to one another or to the substratum.

Sex Pili

Specialized appendages on prokaryotic cells that hold two cells together long enough to transfer DNA during conjugation.

Flagella

The most common structure used by prokaryotes for movement (taxis), which can be scattered over the entire surface or concentrated at one or both ends.

Endospores

Resistant cells formed by certain bacteria during harsh conditions by replicating their chromosome and surrounding it with a durable, protective wall.

Nucleoid

The dense region in a prokaryotic cell where the single circular chromosome is concentrated as a snarl of fibers.

Plasmids

Small, circular rings of DNA in prokaryotic cells that replicate independently of the main chromosome and carry genes for specialized functions like antibiotic resistance.

Transformation

A mechanism of horizontal gene transfer in which a prokaryotic cell absorbs and integrates foreign DNA fragments from its surrounding environment.

Conjugation

The direct transfer of genetic material between two prokaryotic cells that are temporarily joined by sex pili.

Transduction

A mechanism of genetic recombination in which phages (viruses) transfer prokaryotic genes from one host cell to another.

Photoautotrophs

Photosynthetic organisms that harness light energy to drive the synthesis of organic compounds from carbon dioxide ($CO_2$).

Chemoautotrophs

Organisms that require only $CO_2$ as a carbon source and obtain energy by oxidizing inorganic substances such as $H_2S$, $NH_3$, or $Fe^{2+}$.

Photoheterotrophs

Organisms that use light to generate ATP but must obtain carbon in organic form.

Chemoheterotrophs

Organisms that must consume organic molecules for both energy and carbon.

Obligate Aerobes

Organisms that strictly require $O_2$ for cellular respiration.

Facultative Anaerobes

Organisms that use $O_2$ when present but can switch to fermentation or anaerobic respiration in an anaerobic environment.

Obligate Anaerobes

Organisms that are poisoned by $O_2$ and live exclusively by fermentation or anaerobic respiration.

Nitrogen Fixation

The metabolic conversion of atmospheric nitrogen ($N_2$) into ammonia ($NH_3$) performed by certain prokaryotes.

Heterocytes

Specialized non-photosynthetic cells in filamentous cyanobacteria (such as Anabaena) that carry out nitrogen fixation.

Domain

A taxonomic category above the kingdom level; modern taxonomy recognizes three domains: Bacteria, Archaea, and Eukarya.

Extremophiles

Archaea that live in extreme environments unfavorable to most other life, including extreme halophiles and extreme thermophiles.

Extreme Halophiles

Organisms, mostly within Archaea, that thrive in highly saline environments.

Extreme Thermophiles

Organisms, mostly within Archaea, that thrive in extremely hot environments.

Cyanobacteria

Gram-negative photoautotrophs that generate $O_2$ via photosynthesis and from which plant chloroplasts likely evolved through endosymbiosis.

Spirochetes

Helical heterotrophic bacteria that move in a corkscrew fashion using internal helical filaments; includes parasites like Treponema pallidum and Borrelia burgdorferi.

Actinomycetes

A group of Gram-positive bacteria that decompose organic matter in soil.