What Workflows will I need Sample Plating for?

The primary aim of sample plating is to isolate, culture, and enumerate microorganisms, or to grow cells for various experiments and analyses in both molecular biology and proteomics. Sample Plating is commonly used in various workflows such as:

1. Microbial cultures to isolate and identify specific bacterial or fungal species.
2. Cell culture studies in molecular biology for gene expression, drug testing, or other cellular assays.
3. Proteomics experiments to study protein interactions or activities on a solid phase.
4. Colony PCR and other genetic screening methods.
5. Antimicrobial susceptibility testing.

Top Sample Plating Methods

There are several types of sample plating methods, each serving a specific purpose, depending on the experimental goals:

Streak Plating

Purpose: To isolate individual colonies from a mixed sample.

Procedure: Using an inoculating loop, the sample is spread across the agar surface in a specific pattern, typically in three to four quadrants. The intent is to dilute the sample so that by the last quadrant, individual cells are deposited separately on the agar, leading to isolated colonies upon incubation.

Learn more about streak plating

Pour Plating

Purpose: Same as spread plating.

Procedure: A defined volume of liquid sample is mixed with molten agar medium and then poured into a petri dish. As the agar solidifies, microorganisms are embedded in it and will form colonies both on the surface and within the agar.

Learn more about pour plating

Spot Plating

Purpose: Used for assays, comparative growth studies, or rapid screening.

Procedure: Small volumes of different samples are placed as individual spots onto the surface of an agar plate. This method can be used to quickly compare growth conditions or to check multiple strains or treatments at once.

Learn more about spot plating

Spread Plating

Purpose: Counting the number of microorganisms in a sample or for cultivating isolated colonies.

Procedure: A defined volume of liquid sample (often previously diluted) is pipetted onto the center of an agar plate. A sterile bent rod (often glass) or a cell spreader is used to evenly spread the sample over the entire surface of the agar.

Drop Plating

Purpose: A variation of spot plating, but with smaller volumes.

Procedure: Small drops of sample (usually 5-10 microliters) are placed onto an agar plate. Often used for quick visual assays or to test viability.

Replica Plating

Purpose: To transfer multiple colonies from one plate to another, maintaining the same spatial arrangement.

Procedure: A master plate with colonies is pressed against a sterile velvet or similar material. A new agar plate is then pressed against the same piece of velvet, transferring some cells from each colony onto the new plate in the same spatial pattern.

Why is Sample Plating difficult?

1. Technique Sensitivity: Proper isolation and growth require a consistent and gentle technique to prevent damage to cells or colonies.
2. Cross-Contamination: There’s always a risk of introducing contaminants from the environment or other samples.
3. Volume Accuracy: Ensuring the precise volume of the sample is critical for certain quantitative analyses.

Benefits of Automation over Manual Pipetting for Sample Plating:

• Consistency: Automated systems ensure consistent plating across multiple samples.
• High Throughput: Automation drastically reduces the time required to plate many samples.
• Reduced Contamination Risk: With fewer manual interventions, there’s a decreased risk of contamination.
• Accuracy: Automated systems ensure precise volume delivery and consistent spreading, leading to accurate results.