Prokaryotes: Biology for Majors

Flashcards covering key terms and definitions related to prokaryotic biology, including their structure, metabolism, reproduction, diversity, and ecological roles, based on the provided lecture notes.

Prokaryotes

Organisms belonging to two of the three domains of life—Bacteria and Archaea—which were the first inhabitants on Earth and are abundant and ubiquitous.

Bacteria

One of the three domains of life, consisting of prokaryotic organisms.

Archaea

One of the three domains of life, consisting of prokaryotic organisms, often found in extreme conditions.

Microbial Mats

Multi-layered sheets of prokaryotes (mostly bacteria, but also archaea), possibly the earliest forms of life on Earth, starting about 3.5 billion years ago.

Stromatolites

Fossilized microbial mats that are the earliest record of life on Earth; sedimentary structures formed by prokaryotes precipitating minerals out of water.

Anoxic Atmosphere

Earth's early atmosphere, which had no molecular oxygen.

Anaerobic Organisms

Organisms that can grow without oxygen.

Phototrophs

Autotrophic organisms that convert solar energy into chemical energy.

Cyanobacteria

Blue-green algae that evolved from simple phototrophs and began the oxygenation of Earth's atmosphere.

Extremophiles

Bacteria and archaea adapted to grow under extreme conditions.

Radioresistant Organisms

Extremophiles adapted to survive high levels of radiation.

Acidophiles

Extremophiles that thrive at a pH of 3 or below.

Thermophiles

Extremophiles that thrive at temperatures of 60–80 °C (140–176 °F).

Halophiles

Extremophiles that thrive at salt concentrations of at least 0.2 M.

Unculturable Prokaryotes

Over 99% of bacteria and archaea that cannot be grown in a laboratory due to unknown specific requirements.

Biofilm

A microbial community held together in a gummy-textured matrix, consisting primarily of polysaccharides secreted by the organisms, attached to surfaces.

Pili

Hairlike appendages that help bacteria permanently anchor to a surface during biofilm development.

Biological Nitrogen Fixation (BNF)

A process exclusively carried out by prokaryotes (soil bacteria, cyanobacteria, Frankia spp.) that converts atmospheric nitrogen into usable forms for plants.

Cocci

Spherical-shaped prokaryotes.

Bacilli

Rod-shaped prokaryotes.

Spirilli

Spiral-shaped prokaryotes.

Nucleoid Area

The region in a prokaryotic cell where the single, circular piece of DNA is located, as prokaryotes lack a nucleus.

Binary Fission

Asexual reproduction in prokaryotes where the chromosome is replicated, the cell enlarges, pinches inward, and divides into two clone cells.

Transformation

A mechanism of genetic recombination in prokaryotes where a cell takes up prokaryotic DNA directly from the environment.

Transduction

A mechanism of genetic recombination in prokaryotes where a bacteriophage injects DNA into the cell, containing a small fragment of DNA from a different prokaryote.

Conjugation

A mechanism of genetic recombination in prokaryotes where DNA is transferred from one cell to another via a mating bridge.

Archaeal Phospholipids

Differ from bacterial and eukaryotic phospholipids by having branched phytanyl sidechains and an ether bond connecting the lipid to glycerol.

Peptidoglycan

A component found in bacterial cell walls, but absent in archaean cell walls.

Gram-positive Bacteria

Bacteria with a thick cell wall and teichoic acids, which retain the Gram stain.

Gram-negative Bacteria

Bacteria with a thin cell wall and an outer envelope containing lipopolysaccharides and lipoproteins, which do not retain the Gram stain.

Macronutrients

Nutrients required in large amounts by cells to sustain life, such as carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

Micronutrients

Nutrients required in smaller or trace amounts by cells.

Photoautotroph

An organism that obtains energy from light and carbon from an inorganic source (e.g., carbon dioxide).

Chemoheterotroph

An organism that obtains energy from chemical reactions (inorganic oxidation) and carbon from organic compounds.

Epidemic

A disease that occurs in an unusually high number of individuals in a population at the same time.

Pandemic

A widespread, usually worldwide, epidemic.

Antibiotic

A chemical, produced either by microbes or synthetically, that is hostile to the growth of other organisms.

Antibiotic Resistance

The ability of bacteria to survive and grow in the presence of antibiotics, often fostered by the imprudent and excessive use of antibiotics.

Bioremediation

The use of prokaryotes (or microbial metabolism) to remove pollutants from the environment.

Microbiome

The normal microbial flora or gut microbiota, referring to the collective of bacteria living in an individual’s stomach, aiding digestion and protecting against pathogens.