FDE305 Food Microbiology Lab Quiz

FDE305 - Food Microbiology Laboratory: Microscopic Examination of Microorganisms, Microscope Care, and Simple Staining

• Course Focus: Examine microorganisms, use microscopes, and perform simple staining techniques relevant to food microbiology.

Objectives

• Understand the parts and functions of a microscope
• Know how to use a microscope effectively
• Master the preparation and staining of bacterial smears
• Identify basic bacterial shapes following staining
• Properly locate and examine stained bacterial smears

Introduction

• Cytology Defined: The study of cells and their components
• Microscopic Structures: Cellular structures not easily visible without magnification
• Differential Staining: A cytological technique using multiple reagents to highlight specific cellular features
• Simple Staining: Applying a single stain or reagent to highlight specimen features

Introduction: Staining Principles

• Chemical Reactions: Chemicals react with substances, producing color changes, specific to cell type or structure
• Amphoteric Molecules: Cellular proteins and amino acids, can be acid or base depending on environments
• Stain Functionality: To be effective, a stain needs to display color and be able to act as an acid or base

Introduction: Preparing Specimens

• Cell Preparation: To allow observation of microscopic structures, cells need preparation: sufficiently thin layers on slide, enough light passing through sample.
• Smear Preparation (Broth & Solid Media): For broth cultures, the suspension is directly placed on a slide. For solid media, a portion of the growth is emulsified with a liquid on a slide.
• Fixation: Crucial for preventing cell distortion, stopping enzymatic activity that can damage cells if they were to die. This also helps the cells adhere to the slide.

Microscopic Examination of Microorganisms

• Microscope Care: Upright position, keep it 15cm+ away from the table edge. Do not handle lenses directly, ensure that the low-power objective lines up in the working position.
• Avoid Contamination: Inspect tools for contaminants, do not touch lenses with bare fingers, protect microscope from chemicals.
• Oil Immersion: Use oil for enhanced light transmission during high-power viewing. Properly remove any remaining oil using lens paper
• Simple Staining Procedure: Preparation of smear, heat fixation, applying the stain, rinsing, and observation under the microscope.

Simple Staining Procedure Steps

• Smear Preparation: Prepare a smear from a bacterial culture.
• Heat Fixing: Heat-fix the smear.
• Staining: Apply a staining agent to the smear.
• Rinsing: Rinse the excess stain.
• Observing: Observe the stained sample under a microscope with the appropriate objective lens. Note any color (type of stain) or shape distinctions between microorganisms.