Micro Exp 3 Environ

Universiti Tunku Abdul Rahman (Kampar Campus) Faculty of Science, Engineering, and Technology Bachelor of Science (Hons) Biotechnology Year 2 Semester 1 UESB 2142 Laboratory 2A (III) Microbiology Lecturer: Dr. Teh Yok Lan Student’s Name: Cheah Hong Leong Student’s ID: 08AIB03788 Experiment No. 3 Title: Environmental Influences Date: July 20, 2009

Title: Environmental Influences Objectives: –

Examine the effects of temperature on microbial growth of different bacteria.

–

Examine the effects of different osmotic pressure on microbial growth of different bacteria.

–

Examine the effects of pH on different bacteria.

–

Determine

whether the

bacteria being examined are

aerobic, anaerobic,

microaerophilic or aerotolerant. Results: All the tables below record the observation made on day 2 and 4 after incubation that’s on July 22 and July 24, 2009. Table 1: Effects of Different Temperature on Microbial Growth Bacteria 4 oC Pseudomonas

Observations Room Temperature

Clear Broth solution Formation

afruginosa

55 oC

of Clear Broth solution

pellicle and yellow-

Escherichia coli

white sediment Clear Broth solution Formation of white Clear Broth solution

Micrococcus luteus

sediment Clear Broth solution Formation

of Clear Broth solution

yellowish sediment

Table 2: Effect of Osmotic Pressure on Microbial Growth – Sucrose Solution Bacteria Sucrose 0.5%

Observations Sucrose 15% of Formation

Sucrose 30%

Pseudomonas

Formation

afruginosa

yellow-white

Escherichia coli

colonies colonies colonies Formation of white Formation of white Formation of white

Staphylococcus

colonies Formation

aureus

yellow-orange

yellow-orange

yellow-orange

colonies

colonies

colonies

yellow-white

colonies of Formation

of Formation

of

yellow-white

colonies of Formation

of

Table 3: Effect of Osmotic Pressure on Microbial Growth – Sodium Chloride Solution Bacteria NaCl 0.5%

Observations NaCl 15%

NaCl 25%

Pseudomonas

Formation

of No colony observed No colony observed

afruginosa

yellow-white

Escherichia coli

colonies Formation of white No colony observed No colony observed

Staphylococcus

colonies Formation

aureus

yellow-orange

of No colony observed No colony observed

colonies

Table 4: Effect of pH of Medium on Microbial Growth Bacteria pH 5

Observations pH 7 of Formation

pH 9

Pseudomonas

Formation

afruginosa

yellow-white

Escherichia coli

colonies colonies colonies Formation of white Formation of white Formation of white

Staphylococcus

colonies Formation

aureus

yellow-orange

yellow-orange

yellow-orange

colonies

colonies

colonies

yellow-white

colonies of Formation

of Formation

of

yellow-white

colonies of Formation

of

Table 5: Relation of Free Oxygen to Microbial Growth Bacteria Staphylococcus

Observations Colonies only found in lower part of the tube

aureus Escherichia coli Micrococcus luteus

Colonies found throughout the tube Colonies only found on the upper part and surface of the tube

Discussion: Based on Table 1, on both day 2 and 4, bacterial growth for the three bacteria, Pseudomonas afruginosa, Escherichia coli, and Micrococcus luteus were only observed on Broth cultures incubated at room temperature. Bacterial growth was indicated by the formation of pellicles or sediments in the Broth cultures. These results indicate that all of the bacteria examined are mesophiles. They can grow neither in temperature of 4 oC nor 55 oC. All the bacteria examined have maximum growth temperature below 55 oC and minimum growth temperature above 4 oC.

Bacterial growths for all the bacteria were observed in all the plates regardless the concentration of sucrose of the cultures. This indicates that all the bacteria, Pseudomonas afruginosa, Escherichia coli, and Staphylococcus aureus are osmophiles since they can survives in high sucrose concentration environment. For all the bacteria, Pseudomonas afruginosa, Escherichia coli, and Staphylococcus aureus, bacterial growths were only observed on plate with NaCl 0.5% for both day 2 and 4. No bacterial growth was observed on the plates with NaCl 15% and 25%. This indicates that they are all non-halophiles that cannot grow in highly saline environment. They will either die or dehydrated and became dehydrated under highly saline condition and therefore no bacterial growth was observed. However, they can still grow well in culture with NaCl 0.5% indicates that they can tolerate with some reduction of water activity, they are halotolerant. In Table 4, all the bacteria, Pseudomonas afruginosa, Escherichia coli, and Staphylococcus aureus, showed bacterial growth in all the culture with pH 5, 7 and 9. Therefore, based on the results, the three bacteria cannot be differentiated into acidophile, alkaliohile, or neutrophile. The results showed that all the three examined bacteria can grow in culture of pH from 5 to 9; this indicates that all these bacteria have a wide range of pH, from acidic pH to alkali pH, with the optimum pH most probably at neutral pH. Most natural environment have the pH range of 4 to 9, hence the three bacteria are capable to survive in most of the natural habitats.

In Table 5, Staphylococcus aureus only observed to form colonies in bottom part of the tube, which is the anoxic region. This showed that Staphylococcus aureus is anaerobe and most probably obligate anaerobes because no colony was found to form on other region near the oxic region, the upper part of the tube. In contrast, Micrococcus luteus was only found to form colonies on the upper part and surface of the tube, which is the oxic region. Micrococcus luteus is an obligate aerobe which needs oxygen for metabolism and cannot grow without it. Escherichia coli is facultative aerobe that does not need oxygen but grow better with presence of oxygen, therefore, the colonies were found to form throughout the tube, regardless the anoxic or oxic region. They can carry out anaerobic and aerobic respiration. Conclusion: 1. Pseudomonas afruginosa is a mesophile, osmophiles, non-halophile but still

halotolerant, and has a wide range of pH adaptability. 2. Escherichia coli is a mesophile, osmophiles, facultative aerobe, non-halophile but

still halotolerant, and has a wide range of pH adaptability. 3. Micrococcus luteus is a mesophile and obligate aerobe. 4. Staphylococcus aureus is an osmophiles, non-halophile but still halotolerant, has a

wide range of pH adaptability, and obligate anaerobe. References: Madigan, M. T., Martinko, J. M., Dunlap, P. V., & Clark, D. P. (2009). Brock Biology of Microorganisms, 12th ed., San Francisco, CA: Pearson Benjamin Cummings.