Lab 2 Assignment - Bacterial Cells

Names: Section # & Bench #: COMPLETE AS A PAIR! NAME (include partner’s name): Lab 2 - Bacterial Cells ( 10 points ) Due: By next week’s lab ● Complete this sheet, download as Word doc, submit on Canvas Please complete the following questions using your data from today’s lab. 1. Enter your data for the calibration of the ocular micrometer for each objective lens: ( 1 pts ) Objective Lens X (SM lines Y (OM lines) Calibration (µm) 4X 100 40 25 µm 10X 100 100 10 µm 40X 25 100 2.5 µm 2. Enter your data for the following table: ( 2 pts ) 3. Chain # A. Length of chain (# of OU or lines) B. Length of chain in µm C. # of rods in chain D. Length of chain in um/number of rods 1 30 300 µm 20 15 µm 2 32 320 µm 15 21.3 µm 3 35 350 µm 24 14.6 µm 4 32 320 µm 22 14.5 µm 5 30 300 µm 18 16.7 µm Average length of an individual bacterium across all chains (average values from Column D), YOU MUST SHOW YOUR CALCULATION FOR CREDIT (15.0+21.3+14.6+14.5+16.7)/5    =16.4  1

Names: Section # & Bench #: COMPLETE AS A PAIR! 4. Complete the following table based on the results of your Gram stain ( 2 pts ): Sample Cell Morphology Gram stain result (+ or -) A Bacillus   + B Cocci   - C Cocci   + D Spirillum   - To answer the following questions, feel free to refer to your textbook or the internet! 5. Describe the composition of the cell wall of the bacterial sample you analyzed by Gram stain. What result did you obtain, and what can you conclude about the composition of its cell wall? ( 2 pts ) Sample ID: B Conclusions: The gram stain showed cocci gram negative cells which is characterized as a circular pink shaped bacterium. This means that the cell walls don’t have much peptidoglycan and contain an outer membrane of liposaccharides 6. Imagine you are a physician and a patient presents with a bacterial infection in their throat. You prescribe a course of antibiotics, but find the antibiotics to be ineffective. You take a sample from the patient and send it to the pathology lab for a Gram stain, and it returns with a Gram negative result. What aspects of this bacterium would suggest that the antibiotic might have difficulty eliminating the infection? ( 3 pts )   Gram-negative bacteria have a more complex cell wall than gram positive bacteria. The liposaccharide outer membrane of the gram-negative bacterium would likely be preventing the antibiotic from eliminating the infection.  2