Determination of the Atmosphere Oxygen, Research Paper Example

Introduction

Different types of bacteria that live in an environment vary for their need of oxygen in order to perform respiration. Respiration allows the bacteria to produce energy through the oxidation of substrates. There are different oxygen level requirements associated with different type of enzyme systems found in bacteria. There are five groups of oxygen level environments that bacteria are placed in during the experiment, in order to determine the above described differences.

The Oxygen Needs of Different Bacteria

Obligate aerobes need oxygen for growth. As oxygen is the final election acceptor  required to complete the oxidative degradation, it is essential for growth and basic functioning.  Oxidative degradation is also called aerobic respiration.

Microaerophiles also need a certain level of oxygen, but lower than the level that is found in the air. These bacteria use the process of aerobic respiration, but they have an enzyme that is sensitive to oxygen.

Obligate anaerobes do not need oxygen. Their final electron acceptor is not oxygen, like obligate aerobes’, but a different molecule, because they perform anaerobic respiration.

Aerotolerant anaerobes do not need oxygen, either, as their final electron acceptor is different. They are set apart from obligate anaerobes in a way that they use catalysis and they do not die from atmospheric oxygen.

Facultative anaerobes undergo the process of aerobic respiration, however, oxygen can be present or absent, they are indifferent to the oxygen content.  These bacteria get their energy from anaerobic respiration, or by the process of fermentation.

Experiment Details

The purpose of this experiment is to determine the type of environment with different atmospheric oxygen requirements that various bacteria grow in. Measuring the growth of the six different cultures is expected to help determine the amount of oxygen needed for each type of bacteria to grow. The two environments used were thioglycollate broth, which is a liquid media that supports aerobic and anaerobic organisms, and nutrient agar, which is in plate form, and supports many different kinds of organisms that are incubated.

Conditions

There are three plates.

• The first one is placed under a normal atmospheric condition.
• The second plate is placed in an anaerobic pouch
• The last one is placed in a candle jar.

In this experiment we will be able to determine the oxygen sensitivity and need level in bacteria for respiration. In order for respiration take place, substrates need to be oxidized for the actual energy production.

There are five different major groups that the bacteria are placed in, based on their oxygen requirements. These five different groups of microorganisms will grow in a tube in relation to the oxygen tension in the tube. In this experiment, we will be using many a combination of different conditions to establish the oxygen requirements of the five different kinds of bacteria. The two “conditions” or media we will be using are Thioglycollate broth and Nutrient Agar.

Thioglycollate broth is a liquid media or a “holder” that will support the growth of the aerobic and anaerobic organisms. Nutrient Agar is a solid agar that we will be using in a plate form. Te environments will also support the growth of various bacteria that are put in incubation.

Testing

Each one of these organisms will be tested in three conditions of incubation for measuring different results. The first plate of each bacteria will be incubated under usual temperatures, while the other two will be put into an anaerobic pouch, providing oxygen free incubation. The pouch is constructed of a paper gas generating packet, sealed in a foil envelope. Oxygen is absorbed by the wall of the pouch and carbon dioxide is produced creating a anaerobic environment. As a result,  carbon dioxide content inside will be between eight and fourteen percent. Further, a strip that changes color depending on the presence of oxygen will be put into the pouch. When oxygen is present, the strip ill turn red, and if there is no oxygen it will be colorless. The last container used will be protected in a candle jar for incubation. The candle jar is used to create an atmosphere of concentrated oxygen and increased carbon dioxide levels.

Experiment Details

All three containers’ bacteria are expected to create different results. After we place the plates in the jar, the candle will be lit and placed on top of the plates with the lid of the jar being closed tight. The candle will go on burning until there is no oxygen in the space to keep it lit. The light will go out at that point, and the concentration of CO2  will be five to ten percent.

The process of this experiment should also be done within a bacteria free space. There are Bunsen burners that are available to us for cooking and killing any bacteria around or on the plates during the transferring process, used to create this bacteria-free environment.

The experiment was completed as a  group project meticulously and carefully. Using the proper techniques described in class, we labeled each tube carefully according to its correct organism. We also labeled the bottom of the three plates with the names of the organism assigned to our group. We streaked each plate with 3 organisms on the nutrient agar plates that we rubbed with. We then incubated the plates for a week to  provide enough time for the bacteria to show signs of growth. After a week, we compared the three broths that our group vaccinated, and incubated under various atmospheres. We considered the guideline that time taken between opening the foil and sealing the plastic pouches should not exceed for more then a minute. If the contents were exposed too long, it would result in the loss of reactivity and full anaerobic conditions may not be achieved in the pouch. Depending on the bacteria, media, and conditions we placed them in, we expected different growth results.

Results

Based on our experiment with the tubes of thioglycollate broth and the agar plates culture incubated under different atmospheric conditions, we were able to classify most of the bacteria organism under the appropriate group depending on their oxygen requirement. S. aureus, B. subtilis, E. coli, and C. tertium are found to be facultative anaerobes because in the tubes of thioglycollate broth in figure 6A, the bacteria gathers in every part of the tubes, which is a characteristic of a facultative anaerobe. This means that the bacteria is able to use both anaerobic and aerobic respiration. However, in the agar plates culture, there were no growth in the anaerobic pouch incubation, which is odd, since facultative anaerobes can also utilize anaerobic respiration.

As for E. faecalis, it is not clear which group this bacteria falls under. In the tube of thioglycollate broth, the bacteria gathered at the bottom of the tube, which would imply that it is an obligate anaerobe, but the opposite occurred for the agar plates. On the agar plates, it did not show any sign of growth, in any of the different atmospheric conditions.

Based on the results of our experiment, C. sporogenes is an obligate aerobe, because in the thioglycollate broth, it gathers at the very top near oxygen. It can be infer that this bacteria can either be an obligate aerobe or a microaerophile, however, in the agar plate cultures, C. sporogenes showed no signs of growth in the anaerobic atmospheric condition, which implies that it is an obligate aerobe.

It is strange for the anaerobic pouch incubation to show no sign of growth for any bacteria that were used in this experiment. It is unknown whether the procedures were done correctly or not for this part of the experiment, as per the results.

Please check if this is right