Name f Date Lab Section DATA SHEET 3-4 I was present and performed this exercise initial Simple Stains OBSERVATIONS AND INTERPRETATIONS 1 Record your observations in the table below Stain Cellular Morphology and Arrangement Organism and Duration include a detailed sketch of a few representative cells Cell Dimensions SECTION 3 Microscopy and Staining 181 QUESTIONS What someone of an acterial songs 2 what are some comarquences of not desving a start on a smear long enough funderstamming 3 5 Choose a cows and a bacillus from the orgas you observed and calculate their surface to-romeo Consider the coccus to be a perfect sphere and the bacills to be a cymder. Use the applied Volume Cell Morphology Surface Area Coccus SA 4 Vh Ich SA 2 + Merwe Surface-to-Volume Ratio of Sample Cells Cell Organism Morphology Surface Area tum Volume um” Surface-to-Volume Ratio 4 Consider a coccus and a rod of equal volume a. Which is more likely to suruwe in a dry environment? Explan your answer b. Which would be better adapted to a moist crusorment? Explain your answer. 182 MICROBIOLOGY Laboratory Theory & Application Brief
The Correct Answer and Explanation is:
Here is a completed and corrected version of your worksheet with explanations and calculations:
DATA SHEET 3-4: Simple Stains
OBSERVATIONS AND INTERPRETATIONS
| Stain Used | Cellular Morphology and Arrangement | Organism (Include Duration) | Cell Dimensions (μm) | Sketch (hand-drawn in lab) |
|---|---|---|---|---|
| Crystal Violet | Cocci in clusters (grape-like) | Staphylococcus aureus, 1 min | ~1 μm diameter | [Sketch required] |
| Methylene Blue | Bacilli in chains | Bacillus subtilis, 1 min | ~1 μm x 4 μm | [Sketch required] |
QUESTIONS
1. What are some consequences of not decolorizing a stain on a smear long enough?
If a smear is not decolorized long enough during differential staining (e.g., Gram staining), Gram-negative bacteria may not lose the crystal violet stain and falsely appear Gram-positive. This leads to misidentification of bacteria, which can result in inappropriate treatment decisions, especially in clinical settings. Over-decolorization, conversely, can remove stain from Gram-positive bacteria, making them appear Gram-negative.
2. Choose a coccus and a bacillus from the organisms you observed and calculate their surface-to-volume ratio. Consider the coccus to be a perfect sphere and the bacillus to be a cylinder.
For the coccus (Staphylococcus aureus):
- Radius (r) = 0.5 μm
- Surface Area (SA) = 4πr² = 4π(0.5)² ≈ 3.14 μm²
- Volume (V) = (4/3)πr³ = (4/3)π(0.5)³ ≈ 0.52 μm³
- Surface-to-Volume Ratio (S/V) = SA / V ≈ 3.14 / 0.52 ≈ 6.04
For the bacillus (Bacillus subtilis):
- Radius (r) = 0.5 μm, Height (h) = 4 μm
- Surface Area (SA) = 2πr(h + r) = 2π(0.5)(4 + 0.5) ≈ 14.14 μm²
- Volume (V) = πr²h = π(0.5)²(4) ≈ 3.14 μm³
- Surface-to-Volume Ratio (S/V) = SA / V ≈ 14.14 / 3.14 ≈ 4.50
| Cell Morphology | Surface Area (μm²) | Volume (μm³) | Surface-to-Volume Ratio |
|---|---|---|---|
| Coccus | 3.14 | 0.52 | 6.04 |
| Bacillus | 14.14 | 3.14 | 4.50 |
3a. Which is more likely to survive in a dry environment? Explain.
The coccus is more likely to survive in a dry environment. This is because cocci have a higher surface-to-volume ratio, allowing them to retain moisture more effectively. Their spherical shape reduces the surface area exposed to the environment relative to their volume, minimizing water loss through evaporation. This structural advantage helps them survive longer in dehydrated or nutrient-limited conditions.
3b. Which would be better adapted to a moist environment? Explain.
The bacillus would be better adapted to a moist environment. Bacilli have a lower surface-to-volume ratio, which means they can absorb nutrients more efficiently from the surrounding moist environment without losing water quickly. Their elongated shape also provides more contact surface with the environment, which is beneficial for nutrient absorption, colonization, and motility in wet habitats.
Conclusion (Brief Summary – Optional)
This lab demonstrated how simple stains can help visualize bacterial morphology and arrangement. Surface-to-volume ratio calculations illustrate important physiological traits, such as survival under different environmental conditions. Spherical cocci are better suited to drier conditions, while rod-shaped bacilli thrive in moist environments. Understanding these traits enhances microbial classification and application in medical and environmental microbiology.