Microbiology Labs & Cell Structure

Flashcards covering microbiology lab methods, bacterial cell structures, morphology, and staining techniques based on lecture notes.

Inoculation

The introduction of a tiny sample, inoculum, into a container of nutrient medium to cultivate microorganisms.

Inoculum

A tiny sample introduced into a container of nutrient medium for culturing microorganisms.

Sterile

Complete absence of viable microbes.

Aseptic

Refers to the prevention of infection or contamination.

Incubation

The process where inoculated media is placed in a temperature-controlled chamber (incubator) for microbial growth.

Culture

The observable growth of microorganisms that happens in or on a nutrient medium.

Inspection

The examination of cultured microorganisms, often involving staining of the bacteria.

Isolation

The process where individual bacterial cells are separated to grow into discrete mounds of cells called colonies.

Colony

Groups of bacterial cells large enough to be seen without a microscope, resulting from the growth of a single cell.

Smears for Staining

A thin film of material containing microorganisms spread over a slide, typically fixed to kill microbes before staining.

Simple Stains

Stains that use only one basic dye to highlight microorganisms, often to visualize cell shapes and basic structures.

Differential Stains

Staining procedures that use two or more dyes to differentiate between types of bacteria or bacterial structures.

Special Stains

Staining techniques used to color and isolate specific parts of microorganisms, such as endospores or flagella.

Acidic Dye

A dye that carries a negative charge and stains the background rather than the microbial cell itself (e.g., negative staining).

Basic Dye

A dye that carries a positive charge and stains cells directly because they are negatively charged (e.g., methylene blue, crystal violet).

Gram Stain

A differential staining method that classifies bacteria into Gram-positive (purple) and Gram-negative (colorless, or red) groups based on cell wall composition.

Acid-Fast Stain

A differential stain used to identify bacteria that have a waxy cell wall, such as Mycobacterium species.

Prokaryotic Cells

Cells lacking a membrane-bound nucleus and other membrane-bound organelles, including bacteria and archaea.

Eukaryotic Cells

Cells characterized by the presence of a membrane-bound nucleus and other membrane-bound organelles.

Glycocalyx

A sugary coating external to the cell wall, made of polysaccharides and/or polypeptides, that can be organized as a capsule or loose as a slime layer.

Flagella

Long, filamentous appendages responsible for bacterial motility, made of flagellin protein.

Axial Filaments

Endoflagella found in spirochetes, which are bundles of fibrils that arise at the ends of the cell and spiral around the cell.

Fimbriae

Short, hair-like protein appendages on bacterial cells that enable adherence to surfaces and other cells.

Pili

Longer than fimbriae, used for DNA transfer (conjugation) between bacteria and for gliding motility.

Protoplast

A bacterial cell from which the cell wall has been completely removed, typically from a Gram-positive bacterium.

Spheroplast

A bacterial cell from which most of the cell wall has been removed, typically from a Gram-negative bacterium, retaining some outer membrane components.

L form

Bacterial cells that have lost their cell walls and can divide and grow without a wall, often exhibiting pleomorphic shapes.

Simple Diffusion

The net movement of molecules or ions from an area of higher concentration to an area of lower concentration.

Facilitated Diffusion

The movement of molecules or ions across a membrane with the help of a transport protein, from an area of higher concentration to an area of lower concentration.

Osmosis

The net movement of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Active Transport

The movement of substances across a membrane, often against their concentration gradient, requiring energy (ATP) and transport proteins.

Group Translocation

A type of active transport found in prokaryotes where the substance is chemically altered during passage across the membrane, preventing its leakage out of the cell.

Nucleoid

The region in a prokaryotic cell where the main chromosome is located, not enclosed by a membrane.

70s Ribosomes

Ribosomes found in prokaryotic cells and eukaryotic mitochondria and chloroplasts, responsible for protein synthesis.

Inclusions

Reserve deposits or storage bodies found in prokaryotic and eukaryotic cells, used to store nutrients or other substances.

Endospores

Dormant, tough, and non-reproductive structures produced by certain bacteria (e.g., Bacillus, Clostridium) to survive harsh environmental conditions.

Sporulation

The process of endospore formation within a vegetative bacterial cell.

Endospore Germination

The process by which an endospore returns to its vegetative, metabolically active state.

Organelle

A specialized subunit within a cell that has a specific function, typically enclosed within its own membrane in eukaryotic cells.

Endosymbiotic Theory

The theory that eukaryotic cells evolved from prokaryotic cells living inside other prokaryotic cells, leading to organelles like mitochondria and chloroplasts.

Bacteria

Unicellular prokaryotic microorganisms, differentiated by morphology, chemical composition, nutritional needs, energy source, and biochemical activity.

Archaea

A domain of single-celled prokaryotic microorganisms, distinct from bacteria, often thriving in extreme environments.

Morphology

The study of the shapes and arrangements of bacterial cells, detectable by staining.

Bacillus

Rod-shaped bacteria (singular: bacillus).

Coccus

Spherical-shaped bacteria (singular: coccus).

Spiral

Bacteria with various twisted or curved shapes, including vibrio, spirillum, and spirochete.

Vibrio

Spiral bacteria characterized by a curved rod shape (a single bend).

Spirillum

Spiral bacteria with a rigid, wavy shape and external flagella.

Spirochete

Spiral bacteria that are helical and flexible, moving by means of axial filaments (endoflagella).

Star-shaped bacteria (Stella)

Unusual bacterial morphology resembling a star shape.

Rectangular bacteria (Haloarcula)

Unusual bacterial morphology resembling a square or rectangular shape.

Strep-

A prefix indicating a chain-like arrangement of bacterial cells after division (e.g., streptococci).

Staphyl-

A prefix indicating a cluster-like arrangement of bacterial cells after division (e.g., staphylococci).

Tetrad

A group of four cocci arranged in a square.

Sarcina

A cubical packet of eight cocci.

Diplococci

Spherical bacteria arranged in pairs.

Diplobacilli

Rod-shaped bacteria arranged in pairs.

Monomorphic

Bacteria that maintain a single, consistent shape.

Pleomorphic

Bacteria that can exhibit a variety of shapes.

Plasma membrane

The selectively permeable boundary enclosing the cytoplasm of all cells, prokaryotic and eukaryotic.

Cytoplasm

The substance filling the cell, excluding the nucleus, containing organelles and a simple cytoskeleton structure in prokaryotes.

Capsule

A neatly organized and firmly attached type of glycocalyx that protects bacteria from phagocytosis and enables adherence.

Slime layer

An unorganized and loose type of glycocalyx that helps bacteria adhere to surfaces, prevent dehydration, and can be a source of nutrients.

Phagocytosis

The process by which certain cells (e.g., macrophages) engulf and digest particles or microbes; capsules can help bacteria resist this.

Adherence

The ability of bacteria to stick to surfaces or other cells, often facilitated by structures like glycocalyx, fimbriae, or pili.

Flagellin

The globular protein that forms the chains making up bacterial flagella.

Basal body

The protein anchor that attaches bacterial flagella to the cell wall and plasma membrane.

Taxis

A bacterial movement toward or away from a particular stimulus (e.g., chemotaxis for chemicals, phototaxis for light).

Antigen (Flagella H protein)

The flagella H protein acts as an antigen, capable of stimulating an immune response in a host.

Peritrichous

Flagella arrangement characterized by flagella distributed all over the entire surface of the cell.

Monotrichous

Flagella arrangement characterized by a single flagellum at one pole of the cell.

Lophotrichous

Flagella arrangement characterized by a tuft of flagella at one pole of the cell.

Amphitrichous

Flagella arrangement characterized by flagella at both poles of the cell.

Bacterial Cell Wall

A rigid outer layer surrounding the plasma membrane of bacteria, primarily made of peptidoglycan, which maintains cell shape and prevents osmotic lysis.

Peptidoglycan (murein)

A complex polymer composed of disaccharides and polypeptides that forms the rigid portion of bacterial cell walls.

Osmotic lysis

The rupture of a cell due to excessive intake of water; prevented by the bacterial cell wall.

Bacterial pathogenicity

The ability of bacteria to cause disease, to which the cell wall can contribute.

Staining (microorganisms)

Coloring microorganisms with a dye to emphasize certain structures and aid in visualization.

Fixed

The process of attaching microorganisms to a slide, usually with heat or chemicals, which also kills them, to prevent washing off during staining.

Gram-positive bacteria

Bacteria with a thick peptidoglycan cell wall containing teichoic acids, which stain purple with the Gram stain.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane, which appear colorless or red after Gram staining.

Teichoic acid

Alcohol molecule + phosphate group found in the cell walls of Gram-positive bacteria.

Lipoteichoic acid

Teichoic acid linked to the plasma membrane in Gram-positive bacteria.

Wall teichoic acid

Teichoic acid linked to the peptidoglycan layer in Gram-positive bacteria.