Chapter 04 Bacteria and Archaea Microbiology

Flashcards covering key vocabulary related to the structure, function, classification, and characteristics of Bacteria and Archaea, based on lecture notes.

Bacteria and Archaea

Microorganisms that do not have a nucleus or complex, membrane-bound organelles.

Eukaryotes

Organisms that have a nucleus and complex, membrane-bound organelles.

Cytoplasmic (cell) membrane

A thin sheet of lipid and protein that surrounds the cytoplasm and controls the flow of materials into and out of the cell pool.

Bacterial chromosome or nucleoid

Composed of condensed DNA molecules; directs all genetics and heredity of the cell and codes for all proteins.

Ribosomes

Tiny particles composed of protein and RNA that are the sites of protein synthesis.

Cytoplasm

Water-based solution filling the entire cell.

Cell wall

A semirigid casing that provides structural support and shape for the bacterial cell.

S layer

A single layer of protein in some bacteria, used for protection and/or attachment.

Fimbriae

Fine, hairlike bristles extending from the cell surface in some bacteria that help in adhesion to other cells and surfaces.

Outer membrane

An extra membrane found in Gram-negative bacteria, similar to the cytoplasmic membrane but also containing lipopolysaccharide, controls material flow and can be toxic to mammals.

Actin cytoskeleton

Long fibers of proteins that encircle the cell just inside the cytoplasmic membrane and contribute to the shape of the cell.

Pilus

An appendage used for drawing another bacterium close in order to transfer DNA to it.

Capsule

A coating or layer of molecules external to the cell wall, also called a slime layer or glycocalyx, serving protective, adhesive, and receptor functions.

Inclusion/Granule

Stored nutrients such as fat, phosphate, or glycogen deposited in dense crystals or particles that can be tapped into when needed.

Endospore

A dormant body formed within some bacteria that allows for their survival in adverse conditions.

Plasmid

A double-stranded DNA circle containing extra genes in some bacteria.

Flagellum

A specialized appendage attached to the bacterial cell by a basal body that holds a long, rotating filament, providing motility.

Biofilms

Microbial habitats where bacteria (and other organisms) live in cooperative associations with access to food, water, atmosphere, and other beneficial environmental factors.

Coccus

A bacterial shape referring to spheres, oval, bean-shaped, or pointed cells.

Bacillus

A bacterial shape referring to blocky, spindle-shaped, round-ended, filamentous, club-shaped, or drumstick-shaped cells.

Pleomorphism

Variations in size and shape among cells of a single species due to nutritional or slight genetic differences.

Polar flagella

Flagella attached at one or both ends of the cell.

Monotrichous

A flagellar arrangement with a single flagellum.

Lophotrichous

A flagellar arrangement with small bunches or tufts of flagella.

Amphitrichous

A flagellar arrangement with flagella at both poles of the cell.

Peritrichous

A flagellar arrangement where flagella are dispersed randomly over the surface of the cell.

Chemotaxis

Movement in response to chemical signals.

Positive chemotaxis

Movement of a cell in the direction of a favorable chemical stimulus.

Negative chemotaxis

Movement of a cell away from a repellant or potentially harmful compound.

Phototaxis

Movement toward light, exhibited by some photosynthetic bacteria.

Run (flagellar movement)

Counterclockwise movement of the flagella, causing the cell to swim in a smooth, linear direction toward a stimulus.

Tumble (flagellar movement)

Flagellum reverses direction, causing the cell to stop and change course.

Glycocalyx

An external surface coating composed of repeating polysaccharide units that may or may not include protein, also known as a slime layer or capsule.

Slime layer

A loosely formed glycocalyx around the cell that protects it from loss of water and nutrients.

Capsule (glycocalyx)

A glycocalyx that is more tightly bound to a cell than a slime layer, and is denser and thicker; often protects pathogenic bacteria against phagocytic white blood cells.

Cell envelope

Composed of two or three basic layers (cell wall, cytoplasmic membrane, and outer membrane in some bacteria) that act as a single protective unit.

Gram Stain

A staining method developed by Hans Christian Gram in 1884 that delineates two major groups of bacteria (Gram-positive and Gram-negative) based on differences in cell envelope structure.

Gram-positive bacteria

Bacteria with a thick cell wall composed of peptidoglycan and an inner cytoplasmic membrane.

Gram-negative bacteria

Bacteria with an outer membrane, a thin cell wall, and an inner cytoplasmic membrane.

Peptidoglycan

A unique macromolecule found in the cell walls of most bacteria, composed of glycan chains cross-linked with short peptide fragments, providing strong but flexible support.

Selective permeability

A function of the cytoplasmic membrane allowing water and small uncharged molecules to diffuse freely, while requiring special carrier mechanisms for most other molecules.

Nucleoid

A dense area in the cytoplasm where the bacterial chromosome (single circular strand of DNA) is aggregated.

Svedberg (S) units

A measurement of the relative size of cell parts through sedimentation during centrifugation; bacterial ribosomes are 70S, eukaryotic are 80S.

Inclusion bodies

Storage sites for nutrients during periods of abundance within the bacterial cell.

Bacterial cytoskeleton

Long polymers of proteins similar to eukaryotic actin, arranged in helical ribbons around the cell just under the cytoplasmic membrane, contributing to cell shape.

Vegetative cell

The metabolically active phase of a bacterium, able to grow and reproduce.

Sporulation

The process of spore formation, induced by environmental conditions, particularly depletion of nutrients.

Germination (endospores)

The process by which an endospore reverts to a metabolically active vegetative cell when favorable conditions arise, involving exposure to water and a germination agent.

Archaea

A domain of life that shares ribosomal RNA sequences with Eukarya not found in bacteria, but differs from both in unique DNA compaction, membrane lipids, cell wall composition (lacking peptidoglycan), and pilin proteins; often found in extreme habitats.

Methanogens

Archaea that convert CO2 and H2 into methane gas (CH4), typically found in anaerobic environments like swamp mud and digestive systems.

Extreme Halophiles

Archaea that require high salt concentrations to grow, sometimes multiplying in 36% NaCl, and are found in places like salt lakes and mines.

Psychrophiles

Archaea or bacteria that grow at very low temperatures.

Hyperthermophiles

Archaea or bacteria that grow at very high temperatures, typically between 80 °C and 113 °C, found in volcanic waters and submarine vents.

Staphylococcus

A genus of Gram-positive bacteria, typically cocci in clusters or packets, known to cause boils and skin infections.

Streptococcus

A genus of Gram-positive bacteria, typically cocci in pairs and chains, responsible for diseases like strep throat and dental caries.

Bacillus (genus)

A genus of Gram-positive, endospore-forming rod-shaped bacteria, including species like Bacillus anthracis (anthrax).

Clostridium

A genus of Gram-positive, endospore-forming rod-shaped bacteria, including species that cause tetanus, gas gangrene, and botulism.

Mycobacterium

A genus of Gram-positive, non-endospore-forming rod-shaped bacteria, including species that cause tuberculosis and leprosy.

Neisseria

A genus of aerobic Gram-negative cocci, including species that cause gonorrhea and meningitis.

Pseudomonas

A genus of aerobic Gram-negative rods, known to cause pneumonia and burn infections.

Enterobacteriaceae

A family of facultative or anaerobic Gram-negative rods, including genera such as Escherichia, Salmonella, Shigella, and Klebsiella.

Vibrio (genus)

A genus of facultative or anaerobic Gram-negative vibrios, including species like Vibrio cholerae (cholera).

Treponema

A genus of helical and curved Gram-negative bacteria (spirochetes), including Treponema pallidum (syphilis).

Borrelia

A genus of helical and curved Gram-negative bacteria (spirochetes), including species that cause Lyme disease.

Mycoplasma

A genus of bacteria that lack cell walls, including species that cause pneumonia.