Bacteria and Archaea Microbiology

Flashcards covering key vocabulary terms related to bacterial and archaeal cell structure, function, classification, and unique characteristics based on lecture notes.

Bacteria

Single-celled organisms capable of all necessary life activities including reproduction, metabolism, and nutrient processing, lacking a nucleus and complex, membrane-bound organelles.

Archaea

Single-celled organisms that lack a nucleus and complex, membrane-bound organelles, sharing ribosomal RNA sequences with Eukarya, and possessing unique DNA compaction, membrane lipids, cell walls, and pilin proteins.

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, present in all bacteria.

Bacterial chromosome or nucleoid

Composed of condensed DNA molecules that direct all genetics and heredity of the cell and code for all proteins, present in all bacteria.

Ribosomes

Tiny particles composed of protein and RNA that are the sites of protein synthesis, present in all bacteria (70S in bacteria).

Cell wall

A semirigid casing that provides structural support and shape for the cell, present in all bacteria.

Flagellum

A specialized appendage attached to the cell by a basal body, holding a long, rotating filament whose movement pushes the cell forward and provides motility, present in some bacteria.

Fimbriae

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

Pilus

An appendage used for drawing another bacterium close in order to transfer DNA to it, present in some bacteria, typically gram-negative.

Capsule (Glycocalyx)

A coating or layer of molecules external to the cell wall that serves protective, adhesive, and receptor functions; it may fit tightly or be very loose and diffuse, also called slime layer, present in some bacteria.

Endospore

A dormant body formed within some bacteria that allows for their survival in adverse conditions, resisting heat, drying, freezing, radiation, and chemicals.

Plasmid

A double-stranded DNA circle containing extra genes that are nonessential to the cell but may confer protective traits or be used in genetic engineering, present in some bacteria.

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.

Spirillum

A bacterial shape referring to curved, spiral, or corkscrew-shaped cells.

Pleomorphism

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

Biofilm

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

Chemotaxis

Movement of a cell in response to chemical signals, which can be positive (towards a stimulus) or negative (away from a repellent).

Periplasmic Flagella (Axial Filament)

Internal flagella found in spirochetes that are enclosed between the cell wall and cytoplasmic membrane, imparting a twisting or flexing motion to the cell.

S Layer

A surface coating of bacteria consisting of thousands of copies of a single protein linked together, providing protection from environmental conditions, produced mainly in hostile environments.

Gram Stain

A staining method developed by Hans Christian Gram to delineate two major groups of bacteria based on differences in their cell envelope structure.

Gram-positive bacteria

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

Gram-negative bacteria

Bacteria characterized by 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 structural support.

Lipopolysaccharide (LPS)

A component of the gram-negative outer membrane where polysaccharide chains function as cell markers and receptors, and the lipid portion (Endotoxin) stimulates fever and shock reactions when released.

Sporulation

The process of spore formation induced by environmental conditions, typically depletion of nutrients, transforming a vegetative cell into an endospore.

Germination

The process where an endospore returns to a metabolically active vegetative cell upon exposure to favorable conditions, specifically water and a germination agent.

Methanogens

A group of Archaea that convert CO2 and H2 into methane gas (CH4), common in anaerobic environments like swamp mud and animal digestive systems.

Extreme Halophiles

A group of Archaea that require high salt concentrations to grow, some multiplying in up to 36% NaCl.

Hyperthermophiles

A group of Archaea that thrive at very high temperatures, typically between 80 °C and 113 °C, found in places like volcanic waters and submarine vents.

Bergey's Manual of Systematic Bacteriology

A comprehensive classification system for bacteria and archaea that combines phenotypic information with rRNA sequencing to determine evolutionary relatedness.

Bergey's Manual of Determinative Bacteriology

A classification system based primarily on phenotypic characteristics, used for quick identification of unknown bacteria in clinical, teaching, and research labs without focusing on evolutionary backgrounds.

What are the universal components found in all bacteria?

The cytoplasmic (cell) membrane, bacterial chromosome or nucleoid, ribosomes, and cell wall.

Which bacterial structures are present only in some species?

Flagellum, fimbriae, pilus, capsule (glycocalyx), endospore, and plasmid.

What unique features do Archaea possess in their cell envelope and genetics compared to bacteria?

Archaea have unique DNA compaction, membrane lipids, cell walls, and pilin proteins. They also share ribosomal RNA sequences with Eukarya.

What is the primary function of the bacterial cytoplasmic (cell) membrane?

It controls the flow of materials into and out of the cell pool.

What are the two main parts of Lipopolysaccharide (LPS) in gram-negative bacteria, and what is the role of the lipid portion?

LPS consists of polysaccharide chains (which function as cell markers and receptors) and a lipid portion (Endotoxin). The lipid portion stimulates fever and shock reactions when released.