3. Which cell feature defermines the shape of bacterial cells? 4. In your own words, describe the process of using a microscope, including oil immersion microscopy, any tips or tricks you learned during this lab, and any reminders for yourself to make microscopy go more smoothly.

### 3. Cell Feature Determining Bacterial Cell Shape The shape of bacterial cells is largely determined by the structure of the cell wall, particularly the arrangement and composition of the peptidoglycan layer. In many rod-shaped bacteria, a protein similar to actin, called MreB, helps position the synthesis of peptidoglycan so that the cell elongates in one direction. Thus, the interplay between the peptidoglycan layer and the cytoskeletal elements (e.g., MreB) plays a crucial role in defining bacterial cell shape. ### 4. Process of Using a Microscope (Including Oil Immersion Microscopy) 1. **Preparation of the Slide** - Place the specimen on a clean slide and cover it with a coverslip. - Ensure the slide is free of dust and fingerprints to avoid obstructing the view. 2. **Setting Up the Microscope** - Start with the lowest magnification objective to locate the specimen. - Adjust the focus using the coarse and fine focus knobs until the specimen is clearly visible. 3. **Switching to Higher Magnification** - Once the area of interest is located, switch to a higher-power objective lens. - Use the fine focus knob to refine the image. 4. **Oil Immersion Microscopy** - Before switching to the oil immersion objective (usually \(100\times\)), place a small drop of immersion oil on the coverslip directly over the area to be examined. - Carefully rotate in the oil immersion lens ensuring that the lens contacts the oil. - This method increases the numerical aperture of the microscope and enhances the resolution of the image. 5. **Tips and Tricks for Smooth Microscopy** - **Proper Alignment:** Always start with lower magnifications and work your way up to ensure you do not lose the area of interest. - **Cleaning:** Clean the slides, coverslips, and lenses (especially the oil immersion lens) before and after use to prevent residue buildup that can distort the view. - **Handling Oil:** When using immersion oil, ensure that you add only the necessary amount and wipe off any excess oil after observations. - **Lighting Adjustments:** Adjust the light source and diaphragm (or condenser) to avoid glare and enhance contrast. - **Stable Positioning:** Ensure the slide is securely placed on the stage. Use the stage clips firmly but gently to avoid moving the slide unexpectedly. - **Patience:** Take your time switching between objectives and adjusting focus carefully with the fine focus knob to optimize the clarity of the image. - **Note-taking:** Keep a small notebook of any particular observations or adjustments that work well with your specific microscope setup for future reference. Following these systematic steps and tips can help achieve clearer images and a smoother microscopy experience overall.