Module 4: Microbial Metabolism
MB 360: Scientific Inquiry in Microbiology At the Bench
Carlos C. Goller, Ph.D.
NC State University | Department of Biological Sciences
Camila Loyola, Graduate Teaching Assistant
2026-08-19
Overview
Weeks 6–7 · Biolog GEN III phenotypic characterization · Growth measurements · Metabolic interpretation
- Evaluate bacterial growth across many chemical and environmental conditions
- Perform metabolic profiling with GEN III MicroPlates
- Connect phenotypic data to the overall research question
Learning Outcomes
- List safety considerations for propagating microbes
- Explain the purpose of GEN III Biolog plates and metabolic tests
- Describe the features of biofilms
- Discuss the significance of growth curves
- Practice multichannel pipetting; use a turbidimeter to adjust inoculum density
- Collect and interpret growth data from Biolog GEN III plates
- Create a draft for the individual and group projects
Skills & Knowledge
- Follow PPE and microbial safety procedures
- Use Biolog plates and multichannel pipettors correctly
- Adjust bacterial density with a turbidimeter
- Analyze bacterial growth data from 96-well plates
- PPE requirements for microbial work
- Phenotypic assays and growth assessment
- Seeding 96-well plates for bacterial growth
Background: Biolog GEN III
![Biolog GEN III plate layout showing the distribution of test conditions across the wells.]()
Biolog GEN III plate layout with carbon-source and control wells.
Biolog Blood Universal Growth (BUG) agar + GEN III MicroPlates
→ test bacterial growth across 94 conditions at once using metabolic dye chemistry
Lab Safety
Before Lab
- Wear lab coat, goggles, and gloves
- Wipe benches and pipettors with 70% ethanol
During Lab
- Treat all tips as biohazards
- Remove PPE when leaving the lab
After Lab
- Clean work areas and personal items with ethanol
- Dispose of liquids, plates, gloves, and glass using the assigned workflow
- Return reusable materials and wash hands
Methods: Activity 1, Turbidimeter
- Blank the turbidimeter with uninoculated IF-A fluid
- Swab bacteria from the BUG agar plate into IF-A inoculating fluid
- Mix gently and measure turbidity
- Adjust the inoculum to 95% transmittance
Methods: Activity 2, Biolog Plate Preparation
![Illustration showing a multichannel pipette transferring inoculum into a Biolog plate.]()
Loading a Biolog GEN III plate with a multichannel pipette.
- Pour the prepared cell suspension into a multichannel reservoir
- Add 100 µL to each well of the GEN III plate with the multichannel pipette
- Replace tips whenever contamination is possible
- Confirm that every well contains liquid before incubation
- Incubate one plate in the plate reader and one statically at 33 °C for 1 to 2 days
Results & Discussion
- Save and share the raw 600 nm readings
- Export the blank-corrected table as CSV
- Plot growth curves and interpret wells with or without growth
- Identify carbon sources that appear supportive and conditions that inhibited the isolate
Reflection Questions
- What does a turbidimeter measure, and why is it important for this assay?
- Why are BUG-grown bacteria used instead of TSA-grown bacteria?
- How has your multichannel technique changed over the semester?
