Praktikum Mikrobiologi Umum Pembiakan dan Isolasi Mikroba

Summary

This microbiology practical session provides a hands-on introduction to microbial isolation and cultivation. Students learn to prepare nutrient agar, perform various isolation techniques (spread plate, pour plate, streak plate, and airborne isolation), and observe bacterial growth from soil, air, and bacterial cultures like *Serratia marcescens*. The goal is to cultivate pure bacterial cultures and distinguish between desired microbes and contaminants. After performing each technique, the samples are incubated for observation. This session aims to improve students' skills in microbiological isolation and colony identification.

Takeaways

• 😀 The practical session focuses on the isolation and cultivation of microorganisms.
• 😀 The goal of the practical is to teach students how to isolate microbes to obtain pure cultures.
• 😀 Students will learn to differentiate between desired microbes and contaminants.
• 😀 The session covers identifying bacterial colony types and evaluating mistakes in microbial isolation.
• 😀 Materials used in the practical include nutrient agar medium, sterile water, alcohol, and samples like soil and bacteria (Serratia marcescens).
• 😀 Key tools include an inoculating loop (Ose), Bunsen burner, incubator, hotplate, and Petri dishes.
• 😀 The first step in the practical is to prepare the medium, starting with weighing the ingredients and dissolving them in water.
• 😀 Four techniques are used for microbial isolation: spread plate, pour plate, streak plate, and air sampling.
• 😀 The spread plate method involves diluting a soil sample and plating it on agar to isolate bacteria.
• 😀 The streak plate technique involves using an inoculating loop to streak a pure bacterial isolate across an agar plate to obtain single colonies.
• 😀 Air sampling is conducted by exposing a Petri dish with agar to the air to capture airborne microbes, which are then incubated.
• 😀 Incubation of the samples occurs at different temperatures, with 37°C for spread, pour, and air samples, and room temperature for streak plates.

Q & A

What is the purpose of the microbiology practical session?

The purpose of the practical session is to improve students' skills in isolating microbes and obtaining pure cultures, as well as to help students differentiate between desired microbes and contaminants.

What types of bacteria are being isolated in this practical?

The bacteria being isolated are Serratia marcescens and those found in soil and air samples.

What materials are used in this practical session?

The materials used include Nutrient Agar, sterile distilled water (aquadest), 70% alcohol, and a variety of microbiology tools such as inoculating loops, Bunsen burners, incubators, hotplates, petri dishes, and more.

What is the first step in preparing the culture medium?

The first step in preparing the medium is weighing 28 grams of Nutrient Agar, which is then dissolved in 1 liter of sterile distilled water.

How is the prepared medium sterilized?

The prepared medium is sterilized by autoclaving it at 121°C for 15 minutes.

What are the four isolation techniques used in this practical?

The four isolation techniques used are: Spread plate technique, Pour plate technique, Streak plate technique, and Airborne microbial isolation.

How is the spread plate technique performed?

In the spread plate technique, diluted soil samples are transferred to petri dishes and spread evenly using a sterile spreader to isolate microbes. The plates are then incubated to allow microbial growth.

What is the purpose of serial dilution in the practical?

Serial dilution is performed to reduce the concentration of microbes in the sample, allowing for the isolation of individual microbial colonies in subsequent agar plates.

How does the streak plate technique differ from the spread plate technique?

In the streak plate technique, a sample is inoculated onto the surface of the agar in a series of streaks using an inoculating loop, with the goal of isolating individual colonies by progressively reducing the number of microbes in each streak.

What is the incubation process like for the different isolation techniques?

The spread plate, pour plate, and airborne microbial isolation plates are incubated at 37°C for 24 hours, while the streak plate technique is incubated at room temperature for 24 hours.