Microbiology: Prokaryotic Cell Introduction

Flashcards covering key vocabulary related to the introduction, characteristics, structures, and classification of prokaryotic cells, including bacteria and archaea.

Prokaryotic Cells

Cellular organisms belonging to the domains Bacteria and Archaea, characterized by the absence of a nucleus or other membrane-bound organelles, and generally smaller than eukaryotes.

Bacteria

One of the two prokaryotic domains, characterized by the absence of a nucleus and membrane-bound organelles.

Archaea

One of the two prokaryotic domains, characterized by the absence of a nucleus and membrane-bound organelles, often found in extreme environments.

Pilus (plural: pili)

An external, rigid, tubular appendage on prokaryotic cells made of pilin protein, involved in surface attachment and DNA transfer (conjugation).

Ribosomes

Cellular structures found in prokaryotes (70S) and eukaryotes (80S) that are involved in protein synthesis.

Capsule

A distinct, gelatinous, and organized surface coating on some prokaryotic cells, primarily composed of polysaccharides, providing protection and aiding attachment.

Cell Wall

A strong, rigid structure outside the cytoplasmic membrane of most bacteria that prevents cell lysis due to osmotic shock and determines cell shape.

Cytoplasmic Membrane

The semipermeable barrier defining the boundary of a prokaryotic cell, composed of a phospholipid bilayer embedded with proteins, regulating transport.

Cytoplasm

The internal content of a cell, excluding the nucleus region in prokaryotes, where many metabolic reactions occur.

Chromosome

The main genetic material of a prokaryotic cell, typically a single circular double-stranded DNA molecule found in the nucleoid region.

Nucleoid

The gel-like region within a prokaryotic cell where the chromosome(s) are located, lacking a membrane.

Flagellum (plural: flagella)

An external appendage involved in motility, allowing prokaryotic cells to spin like propellers to move through their environment.

Appendages

External structures on prokaryotic cells that facilitate motility (flagella, axial filaments) or attachment and channels (fimbriae, pili).

Axial Filaments (Periplasmic Flagella)

Internal flagella found in spirochetes, enclosed in the space between the outer sheath and the cell wall peptidoglycan, producing cellular motility by twisting.

Fimbriae

Fine, proteinaceous, hairlike bristles emerging from the cell surface, primarily functioning in adherence to other cells and surfaces; can be involved in twitching or gliding motility.

Glycocalyx

A general term for a surface coating on prokaryotic cells, composed primarily of polysaccharides, which can be a capsule or slime layer.

Filament (Flagellum)

The long, thin, rigid helical structure of a bacterial flagellum, composed of the protein Flagellin.

Hook (Flagellum)

The flexible part of a bacterial flagellum that connects the filament to the basal body.

Basal Body (Flagellum)

A stack of rings firmly anchored in the cell wall that anchors the bacterial flagellum and allows it to rotate 360 degrees.

Flagellin

The protein that composes the filament of bacterial flagella.

Atrichous

A bacterial cell lacking flagella.

Monotrichous

A bacterial cell with a single flagellum.

Lophotrichous

A bacterial cell with a tuft of flagella at one end.

Amphitrichous

A bacterial cell with flagella at both ends.

Peritrichous

A bacterial cell with flagella distributed all over the cell surface.

Chemotaxis

The movement of bacteria in response to chemical stimuli, either attracting them to nutrients or repelling them from toxins.

Phototaxis

The movement of bacteria in response to light stimuli.

Magnetotaxis

The movement of bacteria in response to magnetic field stimuli.

Spirochetes

A type of bacteria characterized by flexible spiral shapes and internal axial filaments (periplasmic flagella) that produce a twisting motility.

Sex Pili

Rigid tubular structures (pili) that join bacterial cells for DNA transfer during conjugation.

Conjugation

A process of genetic transfer in bacteria where DNA is exchanged between cells through direct contact via a sex pilus.

Twitching Motility

A type of surface motility involving specialized fimbriae (Type IV), characterized by short, jerky movements.

Gliding Motility

A type of surface motility involving specialized fimbriae (Type IV), characterized by smooth movement across a surface.

Slime Layer

A diffuse, irregular, loosely attached gel-like layer outside the cell wall of some prokaryotes, composed primarily of polysaccharides, offering protection and aiding attachment.

Biofilms

Polysaccharide-encased communities of cells that grow on surfaces, often protecting bacteria from environmental stresses and host immune systems.

Phagocytosis

The process by which certain cells (e.g., immune cells) engulf bacteria or other particles; some bacterial capsules help evade this process.

Cell Envelope

The external covering of a prokaryotic cell, located outside the cytoplasm, typically composed of the cell wall and the cell membrane.

Cell Lysis

The disintegration or bursting of a cell, often due to osmotic shock if the cell wall is compromised.

Gram-positive Bacteria

Bacteria characterized by a thick peptidoglycan cell wall containing teichoic acids, which retain crystal violet stain in the Gram stain procedure, appearing purple.

Gram-negative Bacteria

Bacteria characterized by a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide, which do not retain crystal violet and stain pink with safranin in the Gram stain procedure.

Peptidoglycan

A unique polymer found only in bacteria, making up the main structural component of the cell wall, consisting of alternating N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) subunits linked by tetrapeptide chains.

N-acetylmuramic acid (NAM)

One of the alternating sugar subunits that form the glycan chains of peptidoglycan in bacterial cell walls.

N-acetylglucosamine (NAG)

One of the alternating sugar subunits that form the glycan chains of peptidoglycan in bacterial cell walls.

Tetrapeptide Chain

A string of four amino acids that links adjacent glycan chains in the peptidoglycan structure of bacterial cell walls.

Teichoic Acid

An acid found embedded in the thick peptidoglycan layer of Gram-positive cell walls, involved in cell wall maintenance and cation movement.

Lipoteichoic Acid

A teichoic acid linked to the cytoplasmic membrane in Gram-positive bacteria, potentially stimulating specific immune responses.

Outer Membrane

A unique layer outside the thin peptidoglycan of Gram-negative bacteria, containing lipopolysaccharide, porins, and lipoproteins.

Periplasmic Space

The space between the cytoplasmic membrane and the outer membrane in Gram-negative bacteria, containing the thin peptidoglycan layer and various proteins.

Lipopolysaccharide (LPS)

A molecule composed of lipid A, a core polysaccharide, and an O antigen, found in the outer membrane of Gram-negative bacteria, serving as an endotoxin.

Porin

Proteins found in the outer membrane of Gram-negative bacteria that form channels, allowing molecules to pass through.

Β-lactam Antibiotics (e.g., penicillin)

A class of antibiotics that interferes with peptidoglycan synthesis by preventing the cross-linking of adjacent glycan chains, rendering the cell wall weak, often more effective against Gram-positive bacteria.

Lysozyme

An enzyme found naturally in tears, saliva, and other bodily fluids that breaks the bonds linking glycan chains in peptidoglycan, leading to bacterial cell lysis.

Gram Stain

A differential staining technique used to distinguish between Gram-positive and Gram-negative bacteria based on their cell wall characteristics and ability to retain crystal violet.

Crystal Violet

The primary stain used in the Gram stain procedure, which stains both Gram-positive and Gram-negative cells purple.

Safranin

The counterstain used in the Gram stain procedure, which stains Gram-negative cells pink after they lose crystal violet during destaining.

Mycobacterium

A genus of bacteria that possesses an atypical cell wall containing lipid mycolic acid, making them resistant to certain chemicals and dyes and requiring an acid-fast stain.

Mycolic Acid (Cord Factor)

A waxy lipid found in the cell walls of Mycobacterium species, contributing to their pathogenicity and high resistance to chemicals and dyes.

Acid-fast Stain

A differential staining technique used for diagnosis of infections caused by microorganisms like Mycobacterium, based on the presence of mycolic acid in their cell walls.

Mycoplasma

A genus of bacteria that lacks a cell wall, with their cell membrane stabilized by sterols, making them pleomorphic.

Pleomorphic

Describes bacteria that exhibit variability in shape due to the lack of a rigid cell wall.

Fluid Mosaic Model

The conceptual model describing the cytoplasmic membrane as a dynamic phospholipid bilayer with proteins embedded within it, able to drift about.

Plasmids

Small, circular, supercoiled, double-stranded DNA molecules in bacteria, separate from the chromosome, carrying non-essential but often advantageous genes (e.g., antibiotic resistance).

Svedberg (S) Unit

A unit of measure for sedimentation rate during centrifugation, used to express the relative size and density of ribosomes (e.g., 70S for prokaryotes, 80S for eukaryotes).

Cytoskeleton (Bacterial)

An internal protein framework in bacteria, similar to eukaryotic microfilament protein (actin), likely involved in cell division and controlling cell shape.

Storage Granules (Inclusions)

Accumulations of polymers within bacterial cells, synthesized from excess nutrients, serving as reserves of energy or building blocks.

Gas Vesicles

Structures found in some aquatic bacteria that contain gas, allowing the cells to control their buoyancy.

Endospores

Unique, highly resistant, dormant cells produced by certain bacteria (e.g., Bacillus, Clostridium) that can survive harsh conditions and later germinate into metabolically active vegetative cells.

Vegetative Cells

Metabolically active and reproducing bacterial cells, in contrast to dormant endospores.

Coccus

A spherical bacterial cell shape.

Bacillus

A rod-shaped bacterial cell shape.

Coccobacillus

A very short and plump rod-shaped bacterial cell.

Vibrio

A gently curved or comma-shaped bacterial cell.

Spirillum

A spiral-shaped bacterial cell, often S-shaped and rigid.

Diplobacilli

Rod-shaped bacteria arranged in pairs.

Streptobacilli

Rod-shaped bacteria arranged in chains.

Diplococci

Spherical bacteria arranged in pairs.

Streptococci

Spherical bacteria arranged in chains.

Tetrads

Spherical bacteria arranged in groups of four.

Staphylococci

Spherical bacteria arranged in irregular, grape-like clusters.

Sarcina

Spherical bacteria arranged in cubical packets of eight or more cells.

Serology

The study of serum and immune responses, used in microbiology to identify bacteria based on their antigenic makeup (e.g., using antibodies).

Genetic Analysis/PCR

Molecular techniques, such as Polymerase Chain Reaction, used to identify and classify bacteria based on their specific genetic information (DNA/RNA sequences).

Bergey’s Manual of Determinative Bacteriology

A comprehensive resource used for the classification and identification of known prokaryotes, primarily based on genetic information to determine phylogenetic relationships.

Species (Bacterial)

A collection of bacterial cells that share an overall similar pattern of traits, distinguishing them from other bacterial groups.

Strain

A subspecies culture derived from a single parent that differs in structure or metabolism from other cultures of the same species (e.g., biovars, morphovars).

Type (Bacterial Subspecies)

A subspecies that shows differences in antigenic makeup (serotype), susceptibility to bacterial viruses (phage type), or pathogenicity (pathotype).

Serotype (Serovar)

A type of bacterial subspecies distinguished by differences in antigenic makeup.

Phage Type

A type of bacterial subspecies distinguished by susceptibility to particular bacterial viruses (bacteriophages).

Pathotype

A type of bacterial subspecies distinguished by differences in pathogenicity.