Question

Date _2-20-20 Name: Lab Report: 11 Gas Requirements for the Growth of Bacteria 1 What was the purpose of this laboratory experiment? ard t1 boctania loeabeal on To Dolatbt aml tola vt their geua Draw the growth pa tterns in thioglycollate broth for each of the bacteria. 2. Clostridium butyricum Escherichia coli Pseudomonas aeruginosa 3. Compare the differences among obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophiles and aerotolerants. 4. Explain the role of the enzymes superoxide dismutase, catalase and peroxidase

Answer 1

THE aim of the experiment can be well written as:

To isolate and identify bacteria based on their oxygen / air requirement .

drawing the growth patterns:

at first we should know that

• Clostridium butyricum: obligate anaerobic ( they gather at the bottom to avoid oxygen)

• E. coli : facultative anaerobic ( they gather mostly at the top since aerobic respiration is the most beneficial one : but as a lack of oxygen does not hurt them, they can be found all along the test tube)

• Pseudomonas aeruginosa : obligate aerobe or obligate aerobic (gather at the top of the test tube to get maximum oxygen )

their growth in the thioglycolate tubes will be as follows:

DIFFERENCE BETWEEN OBLIGATE AEROBES , OBLIGATE ANAEROBES, FACULTATIVE ANAEROBES, MICROAEROPHILES , AEROTOLERANT

OBLIGATE AEROBES	OBLIGATE ANAEROBES	FACULTATIVE ANAEROBES	MICROAEROPHILES	AEROTOLERANT
gather at the top of tube, requires oxygen strictly to respire.	gather at the bottom of the tube to avoid oxygen.	found all along the tube . respire in presence of oxygen when present but less or no oxygen does not do them any harm as they can switch from aerobic to anaerobic form .	gather at the upper part of the test tube but not at the top because they do require oxygen but in very low amount.	not at all affected by presence of oxygen and are found evenly spread all along the tube.
presence of catalase and SOD	lacks catalase and SOD	has catalase and SOD enzymes	lacks catalase and SOD this explains why they undergo death when exposed to large amount of oxygen	only SOD present

SOD : superoxide dismutase

ROLE OF THE ENZYMES :

CATALASE : It ia a common enzyme found in all the cells exposed to oxygen. it is an enzyme which breaks down harmful and toxic hydrogen peroxide into oxygen and water. thus it is said to reduce toxicity due to peroxide formation. after the action of catalase the oxygen can be seen bubbling off the reaction region.

SOD superoxide dismutase : it is an enzyme which catalyses the conversion of two superoxide anions into a molecule of hydrogen peroxide and oxygen  

the reaction is as follows :2O₂^- + 2H⁺ -----> H₂O₂ + O₂

PEROXIDASE: IT is known to catalyse the cleavage of hydrogen peroxide into water and an activated donor molecule.

reaction : L ascorbic acid + H₂O₂ ------> oxidised e donor L dehydro ascorbic acid + 2 H₂O

hope it helps :)