Lab Practical 1 Study Guide Flashcards

Flashcards covering key vocabulary terms, definitions, and concepts from the Lab Practical 1 Study Guide, including microscopy, staining techniques, media types, bacterial identification methods, and related microbiological principles.

Gram Staining

A differential staining technique used to classify bacteria based on their cell wall composition into Gram-positive (purplish blue) and Gram-negative (reddish pink).

Oil Immersion Objective Lens

A high magnification lens (100X) used in microscopy, requiring immersion oil to improve resolution.

Gram-positive (G+)

Bacteria that retain the crystal violet stain and appear purplish blue after Gram staining, due to their thick peptidoglycan layer.

Gram-negative (G-)

Bacteria that do not retain the crystal violet stain and appear reddish pink after Gram staining, due to their thinner peptidoglycan layer and outer membrane.

Total Magnification

Calculated by multiplying the magnification of the ocular lens by the magnification of the objective lens.

Wet Mount Preparation

A method to observe live, unstained specimens, allowing for the study of true motility and relative size without the alterations caused by fixing and staining.

True Motility

Directed, purposeful movement of microorganisms, often observed in wet mount preparations.

Brownian Motion

Random jiggling movement of particles caused by collisions with water molecules, not indicative of true motility.

BSL Levels (Biosafety Levels)

Guidelines classifying microbial agents into categories related to their risk of infection and severity of disease, dictating appropriate laboratory practices and containment.

Aseptic Technique

A set of practices designed to prevent contamination of cultures, media, and other sterile materials during laboratory procedures.

Heat Fixation

A physical method of fixation used for smears, which adheres cells to the slide, kills the bacteria, and increases their affinity for stains.

Acidic Stains

Stains with a negatively charged chromophore that are repelled by the negative charge of bacterial cells, thus staining the background and not the cells (e.g., in negative staining).

Basic Stains

Stains with a positively charged chromophore that are attracted to the negatively charged components of bacterial cells, thus staining the cells directly.

Differential Stains

Staining techniques that use multiple dyes to distinguish between different types of cells or structures based on their staining properties (e.g., Gram stain, endospore stain, capsule stain).

Negative Staining

A staining technique that uses acidic stains to color the background, leaving the cells clear. It is considered more accurate for morphology determination as it avoids heat fixation and cell distortion.

Agar

A polysaccharide extracted from seaweed, used as a solidifying agent in microbiological growth media because it is not metabolized by most bacteria and melts at high temperatures before solidifying.

Enriched Media

Culture media supplemented with extra nutrients (e.g., blood, serum) to support the growth of fastidious (picky) microorganisms.

Chemically Defined Media

Culture media where the exact chemical composition, including all ingredients and their quantities, is known.

Complex Media

Culture media that contain ingredients like extracts or digests (e.g., yeast extract, peptone) whose exact chemical composition is not precisely known.

Selective Media

Culture media designed to inhibit the growth of certain microorganisms while promoting the growth of others, often by containing inhibitory agents.

Differential Media

Culture media that allows for the visual differentiation of microorganisms based on their metabolic characteristics, often indicated by color changes or other reactions.

Streak Plate Method

A technique used to isolate pure colonies from a mixed bacterial culture by physically separating cells over the agar surface of a petri dish.

Serial Dilution

The process of sequentially diluting a concentrated solution or culture, typically used to reduce the microbial concentration to a countable number.

True Pathogen

A microorganism capable of causing disease in healthy individuals with intact immune systems.

Opportunistic Pathogen

A microorganism that normally does not cause disease in a healthy individual but can cause disease in a host with a compromised immune system or when introduced into an unusual body site.

Nosocomial Infections

Infections acquired by patients in a hospital or other healthcare setting, often caused by opportunistic pathogens.

Urease Test

An enzymatic assay that detects the presence of the enzyme urease, which hydrolyzes urea into ammonia and CO2, often turning the medium pink if positive (e.g., by Helicobacter pylori).

Catalase Test

An enzymatic assay that detects the presence of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen gas, indicated by the production of bubbles.

Oxidase Test

An enzymatic assay for the presence of cytochrome c oxidase, an enzyme involved in the electron transport chain, which can be detected by a color change on a test strip.

Helicobacter pylori

A urease-positive bacterium prominently associated with ulcers of the stomach and small intestine.