Prokaryotes and Cyanobacteria (Lecture Notes)

Vocabulary flashcards covering key terms and concepts from the lecture notes on prokaryotes, their structures, metabolism, diversity, cyanobacteria, and related ecological roles.

Prokaryote

A unicellular organism lacking a membrane-bound nucleus; DNA resides in the nucleoid.

Nucleoid

Central region in a prokaryotic cell where the circular chromosome is located, not enclosed by a nucleus.

Plasmid

Small circular DNA that replicates independently of the chromosome.

Cytoplasm

The interior of the cell; in prokaryotes it is unstructured and ribosome-rich with no membrane-bound organelles.

Ribosome

Molecular machines for protein synthesis; prokaryotic ribosomes are 70S.

Cell wall

A layer that gives shape and rigidity; in bacteria, often contains peptidoglycan.

Peptidoglycan

Polymeric compound that strengthens the bacterial cell wall; a hallmark distinguishing Bacteria from Archaea.

Gram stain

Differential staining that divides bacteria into Gram-positive (purple) and Gram-negative (pink) based on cell wall structure.

Gram-positive

Bacteria that retain the Gram stain due to a thick peptidoglycan layer.

Gram-negative

Bacteria that do not retain the Gram stain after decolorization and have an outer membrane.

Glycocalyx (capsule)

A slimy outer layer, mostly polysaccharides, aiding attachment and desiccation resistance.

Capsule

Glycocalyx; an outer layer that helps bacteria attach to surfaces and resist drying.

Flagellum

A long, whip-like appendage used for motility.

Fimbriae

Short, numerous appendages for attachment to surfaces.

Pili

Longer than fimbriae; few in number; used for DNA transfer (conjugation).

Binary fission

A simple asexual cell division producing two genetically identical offspring.

Conjugation

DNA transfer between bacteria via a pilus, contributing to genetic recombination.

Transformation

Uptake of free DNA from the environment by a competent cell.

Transduction

DNA transfer between bacteria mediated by bacteriophages.

Endospore

Dormant, highly resistant cell form that helps bacteria survive harsh conditions.

Heterotroph

Organism that obtains carbon from organic matter.

Saprophyte

Heterotroph that decomposes dead organic matter; important for nutrient recycling.

Autotroph

Organism that fixes CO2 to build organic matter; energy from light or inorganic chemicals.

Photosynthetic autotroph

Autotroph that uses light energy to drive carbon fixation (e.g., cyanobacteria).

Chemosynthetic autotroph

Autotroph that derives energy from oxidation of inorganic compounds.

Aerobe

Organism that requires oxygen for respiration.

Anaerobe

Organism that does not use oxygen for respiration.

Obligate (strict) anaerobe

Killed by oxygen.

Facultative anaerobe

Can grow with or without oxygen.

Psychrophile

Microorganism that grows at 0°C or lower and tolerates cold.

Thermophile

Microorganism that prefers high temperatures; optimum growth below 80°C.

Extreme thermophile

Organism with growth optimum above 100°C; found in very hot environments.

Cyanobacteria

Photosynthetic blue-green bacteria that fix nitrogen and release oxygen.

Chlorophyll a

Primary photosynthetic pigment in cyanobacteria and plants.

Phycobilins

Accessory pigments in cyanobacteria (phycocyanin blue, phycoerythrin red).

Thylakoid

Internal membrane system in cyanobacteria where photosynthesis occurs.

Nitrogen fixation

Conversion of N2 to NH3 usable by organisms; performed by nitrogenase in cyanobacteria.

Heterocyst

Specialized nitrogen-fixing cell in some filamentous cyanobacteria.

Akinete

Thick-walled dormant cell in cyanobacteria that resists heat and drought.

Endosymbiotic theory

Idea that organelles like chloroplasts originated from engulfed bacteria living in symbiosis.

Stomatolite

Sedimentary structures formed when cyanobacteria bind calcium-rich sediments.

Mucilaginous sheath

Pigmented, gelatinous outer layer surrounding cyanobacterial filaments.

Filamentous cyanobacteria

Cyanobacteria that grow as long filaments and may form large masses or colonies.

Hormogonia

Fragmented filaments that disperse to form new cyanobacterial colonies.

Phylum Chlorobia

Purple and green sulfur bacteria; anaerobic photosynthetic bacteria often using sulfur compounds.

Purple and green bacteria

Anaerobic phototrophic bacteria (Chlorobia) using sulfur compounds or other substrates.

Bioremediation

Use of microbes or their enzymes to detoxify environmental pollutants.

Archaea

Domain distinct from Bacteria; many extremophiles; cell walls typically lack peptidoglycan.

Diversity of prokaryotes

Two domains (Bacteria and Archaea) with many phyla; Cyanobacteria is a bacterial phylum.

Growth in cyanobacterial blooms

Rapid, dense growth in nutrient-rich water that can deplete oxygen and produce toxins.

Cyanobacteria blooms toxins

Toxic substances produced by some cyanobacteria that can affect animals and humans.

Oxygenic photosynthesis

Photosynthesis that releases oxygen as a byproduct, as in cyanobacteria.

Stomatalites

Layered sedimentary structures formed by cyanobacterial mats (often in aquatic settings).