York College - CUNY Bio 265L Lab Notes

Lab Syllabus

  • Overview of syllabus format and expectations for the course.

Safety in the Laboratory

  • Importance of safety in laboratory practices.

  • Participants required to take a safety quiz to assess understanding of safety protocols.

The Microscope

  • Essential tool for biological examination.

  • Key components and their functions:

    • Eyepiece (Ocular lens): Magnifies the image, typically 10x.

    • Objective lenses: Different magnifications, such as 4x, 10x, 40x, and 100x.

    • Stage: Platform for placing slides.

    • Illuminator: Provides light to view the specimen.

    • Condenser: Focuses light onto the specimen.

    • Diaphragm: Adjusts the amount of light passing through the specimen.

    • Nosepiece: Holds and enables rotation of objective lenses.

  • Key concepts of microscopy:

    • Magnification: Ability to enlarge the image of a specimen.

    • Resolution: Clarity of the image; the ability to distinguish two close objects as separate. (Expressed in terms of distance, usually in micrometers μm.)

    • Contrast: Difference in light intensity between the specimen and the background, critical for visibility.

First Set of Slides: Observation of Morphology and Cellular Arrangement

  1. Coccus (spherical bacteria):

    • Diplococcus: Example - Neisseria gonorrhoeae (causes gonorrhea, a sexually transmitted disease - STD).

    • Clusters of cocci: Example - Staphylococcus (appears in grape-like clusters).

    • Chains of cocci: Example - Streptococcus (appears in chains).

  2. Bacillus (rod-shaped bacteria):

    • Mixed bacillus and examples:

      • Single bacillus: Example - Bacillus anthracis (causes anthrax).

      • Diplobacillus: Paired rod-shaped.

      • Streptobacillus: Rods arranged in chains.

  3. Spirillum (spiral-shaped bacteria):

    • Example - Spirillum volutans (notable for its helical shape).

  4. Spirochete (flexible, spiral-shaped bacteria):

    • Example - Treponema pallidum (causes syphilis, an STD).

Second Set of Slides: Observation of Special Structures / Significance in Clinical Microbiology

  1. Bacterial Capsule:

    • Example - Klebsiella pneumoniae (the capsule aids in evading the host's immune response).

  2. Endospores:

    • Function: Survival mechanism for bacteria under adverse conditions.

    • Location of endospores:

      • Central: Endospores located in the middle of the cell.

      • Subterminal: Endospores located near one end of the cell.

      • Terminal: Endospores located at the end of the cell.

    • Example - Bacillus anthracis associated with anthrax disease.

  3. Flagella and Motility:

    • Role in bacterial motion.

    • Types of flagellar arrangement:

      • Monotrichous: Single flagellum at one end.

      • Amphitrichous: One flagellum at each end.

      • Lophotrichous: Two or more flagella at one end.

      • Peritrichous: Flagella distributed all over the bacterial cell surface.

      • Amphilophotrichous: Flagella at both ends of the bacterium, in clusters.

    • Examples - Spirillum volutans, Proteus vulgaris (notable for their motility).