Identifying the Bacteria Essay

The purpose of this lab is to identify unknown #24 found in the different bacteria culture. The process of identification is made possible through a series of biochemical tests that separate the bacteria based on their characteristics using aseptic techniques. It is critical that a student follows the procedures since this is the same methods used by professional to identify the cause of disease and establish the right treatment (Goldman and Lorrence 8). Therefore, adhering to the detailed process and aseptic techniques is critical to the overall outcome of the experiment contamination from other microorganisms. The unknown was correctly identified as Citrobacter freundii.

Prokaryotes are made up of millions of microorganism which up to this time only one percent have been studied and described in detail.  The bacteria serve a different purpose in human lives. A few of those are non-pathogenic thereby being beneficial to an individual well-being. For example, Escherichia coli

bacteria are found in the human digestive tract t help in the digestion process.  Others are useful in food production such as rhizobium that converts nitrogen in the soil.  However, there are other bacteria that can be pathogenic to humans which cause illness and become fatal if left untreated (Tille 4). The capacity to identify the microorganism responsible for an infection helps in selecting the appropriate antibiotic medication and therapy duration. That means the knowledge on characteristics of this bacteria is critical to making the right decision.

Citrobacter freundii was the unknown bacteria in the experiment. It belongs to gram-negative bacilli group, rod-shaped with an average length of 1-5 um. A few of them are non-motile, but the majority have the body form covered with flagella which help in movement. It exhibits the characteristics of facultative anaerobe which gives it the ability to manufacture ATP through anaerobic respiration in the presence of oxygen and the same time is able to carry out the process of fermentation in the absence of oxygen. In addition to being able to grow on glycerol, it can metabolize citrate or lactose as its only carbon source. They can be found in the natural environments such as water, sewage, soil, food and organs of diseased animals such as reptiles and amphibians.  In soil, they can convert nitrates to nitrites and also ferment glucose. Citrobacter freundii is known to be an enteric pathogen.

Lab 9

Material

Inoculating loop

Test tube rack

Bunsen burner

Sharpie or Wax pencil

Sterile test tube

1 –mL pipets

Pipetter

Bacterial cultures

37oC incubator

Phenol red glucose broths

Phenol red sucrose broths

Phenol red lactose broths

Phenol red mannitol broths

Startch agar plates

MR-VP broths

Barrit’s  Reagents A and B

Procedures

Carbohydrate Fermentation

The first procedure required each tube for carbohydrate fermentation to be labeled according to the type of carbohydrate contained and the names of bacteria to be inoculated with. Then an inoculating loop was used to transfer a bacterial culture to the broth aseptically. The same procedure was repeated for all the tubes while at the same time avoiding the Durham tube when the Glucose broth is being inoculated. After 24-48 hours of incubation at 37OC, the color change in the medium was observed. According to the lab manual, a yellow color indicates acid production from fermentation of carbohydrates. On the other hand, if a bubble is collected in the Durham tube is an indication of also carbohydrate being fermented in the tube. The results in Table 1 were compared.

Starch Hydrolysis

In this procedure the tubes were labeled with the student’s initials and the bacterial that was going to be inoculated with. The starch plate was divided into half which meant that two organisms were going to be inoculated in the same plate. In line with the aseptic technique, an inoculating loop was used to transfer the bacteria culture to each side of the plate thereby creating single streak.  The plate was incubated at 37oC for 24-48 hours. On the second day, an iodine solution was added to the plate to a level where only the bottom is covered.  The experiment was given a few minutes to allow the iodine black/purple color to spread. From the lab manual starch is hydrolyzed if a clear/yellowish zone is formed around the bacterial growth. The result we compared with those in Table 1.

Methyl Red-Voges Proskauer (MR-VP)

Each MR-VP tubes were labeled with the student’s initials and the bacterial names to be inoculated.  The bacteria culture was transferred to the broth using the inoculating loop while observing the aseptic technique. The procedure was repeated to all the tubes and then incubated for 24hours at 37OC. On the second day, 1 mL of the MR-VP culture was pipetted into a small sterile test tube.  Each organism transferred used its own pipet and new tube. After the transfer, ten methyl red indicator drops were added to the larger MRVP tube and swirled. A yellow color of the indicator means a negative result. Voges-Proskauer test was done on the second small tube with the 1mL of MR-VP culture. In the tube 12 drops of Barritt’s A reagent and four drops of Barritt’s B reagent were added one after the other. The tube was shaken in circular motion and left to settle for ten minutes. A positive result is exhibited by deep red color while negative results are shown by yellowish-brown color. After the observation the results were compared with table 1.

Citrate Utilization

In this procedure the tubes were also labeled with the student’s name and the type of bacteria to be inoculated.  While following the aseptic technique, the bacteria culture was transferred to the slant using an inoculating loop and the procedure repeated for all the tubes. After 37OC incubation for 24 hours, the color changes in the medium were recorded. A blue color indicates a positive result while greenish media color indicates a negative result. Then the result was compared to table 1.

Lab 10- selective and Differential Media

Materials

Inoculating loop

Test tube rack

Bunsen burner and lighter

Sharpie or Wax pencil

Bacterial cultures

37oC incubator       

 Tryptic Soy Agar (TSA), Phenylethanol Agar (PEA), Levine Eosin-Methylene Blue Agar(EMB),Enriched Blood Agar(Blood), Mannitol Salt Agar( MSA), Hektoen Enteric Agar( H-E), Columbia CAN Agar(CNA)

Procedure

Bacterial cultures and plate numbers were obtained according to the instructor directions.  Each plate was labeled based on the media and group information.  Thereafter the plates were divided in reference to the organisms and labeled accordingly and inoculated by all the 7 types of media. The bacteria were transferred to into the each medium aseptically using the inoculating loop and incubated at 37OC for 24-48 hours.  The result was recorded for each organism in all the media. The TSA plate was used as a control to observe the normal growth and be able to compare with the growth levels of the mediums. This was important when observing if the growth rate of the organism had been reduced because of the medium.

Lab 11- Psychological characteristics of Bacteria: Nitrogen metabolism

Material

Inoculation needle, Inoculation loop

Hydrolysis of Gelatin

Nutrient gelatin agar deep( 1 tube per organism)

Indole production

Tryptone broth (1 tube per organism)

Day: Kovacs reagent

Hydrogen sulfide production

Peptone iron agar(1 tube per organism)

Urea hydrolysis

Urea broth (1 tube per organism)

Nitrate reduction

Nitrate A, Nitrate B, Zinc Dust,

Tooth picks

Procedure

Tubes with nutrient gelatin were obtained and labeled according to organisms being tested. The instructor set aside one uninoculated gelatin tube to be incubated alongside the others. The nutrient gelatin tubes were inoculated by scoping a small of portion of the bacteria using a sterile inoculating needle.  Then ¾ of the sterile needle was stabbed into the center of the agar while making sure the there is no contact with the tubes bottom or sides. The gelatin tubes were then placed in the rack at the instructor’s desk which was followed by a 24 hour incubation at 37OC and a one to two hours at room temperature. One the second day, the gelatin tubes were checked if they have solidified starting with the uninoculated tube.

For Indole production, one tube of Tryptone broth was obtained and labeled based on the organism to be tested. A sterile inoculating loop was used to mount the tubes with the portion of the bacteria and incubated for 24-48hours at 37OC.  After the incubation, on the second day ten drops of Kovac’s reagent were added to the Tryptone broth.

Hydrogen Sulfide Production, a peptone iron agar tube was obtained and labeled according the bacteria being tested. The tubes were then inoculated with a portion of the bacteria using a sterile inoculating needle. The needle was stabbed three-quarter of the tube while making sure that there is no contact with the bottom or side of the tube. A 24 hour incubation was conducted at 37oC. The media was then examined on the second day for black precipitate and the result recorded.

For Urea hydrolysis, a tube of urea broth was obtained and labeled according the organism being tested. The tubes were then inoculated with a portion of the bacteria using a sterile inoculating loop and being mixed into the urea broth. A 24 hour incubation was conducted at 37oC followed by an examination on the second day for the presence of hot pink to red color. The results were recorded.

While examining nitrate reduction, a tube was obtained and labeled according to the organism being tested.  A` sterile loop was used to collect a small amount of the bacteria and used to inoculate the tubes to mix with the broth. The Durhum tube was set aside not to be disturbed as this can allow entry of oxygen bubbles thereby interfering with the experimental results. The tubes were incubated for 24hours at 37oC.  On the second day 3 drops of nitrate reagent A were added in each test tube after the incubation followed by 3 drops of nitrate reagent B.  A red color indicates the presence of nitrite in the tubes. The procedure was to be continued if a yellow or clear color of the medium is observed.  A small amount of Zinc dust was to be added using a toothpick to only tubes that had not turned red.  The durhum tube was observed for any gas bubbles.

Lab 12- Miscellaneous Reactions

Materials

One TSA plate for each organism to e tested, hydrogen peroxide, oxidase reagent, toothpicks, sterile Q-tips, DNase Agr inoculating needle/loop, one bile of esculin agar, and one motility agar,

Procedure

A streak plate was prepared for each organism to be tested and incubated for 24 hours at 37oC.  The first experiment was the catalase test.  A hydrogen peroxide drop was added to a clean slide of each organism to be tested. Two organisms were placed per slide separated by a target circle.  A toothpick was used to transfer a small amount of the bacteria culture into the clean slide from the streak plate.  Then in a gentle manner the colony was mixed into the hydrogen peroxide. A positive resulted was to be indicated by the appearance of bubbles. In the second test, a sterile Q-tip was obtained and for each organism and placed two per each slide. Then a toothpick was used to transfer a small portion of the culture from a streak plate to a clean slide. The Q-tip was laid on the labeled paper towel so as to keep track of each organism.  A positive reaction for oxidase is observed by the color change from purple to pink.  The brown color on the sides of the Q-tip was not an indication of a positive result.

In the third experiment DNase test, the plates were divided into three sections using a marker.  A circle was drawn in each section and using a sterile loop, each of the organisms was inoculated into each circles. The plates were the incubated for 24 hours at 37oC. The result was observed and positive result for DNase production is shown by the disappearance of the blue agar color surrounding the bacterial growth. 

In another experiment testing esculin hydrolysis, a sterile inoculating needle was used to inoculate the esculin tubes at the center and three-quarter to the bottom. The plates were then incubated at 37OC for 24 hours which was followed by an observation.  A positive result was indicated by the media turning black which shows esculin hydrolysis.

In the last experiment examining motility, a sterile inoculating needle was used to stab three-quarter of motility tubes to the bottom and at the center.  There was 24 hour incubation at 37OC which was followed by an observation. A well-defined growth along the stab line is an indication of non-motile bacteria while motile bacteria are shown by cloudy growth.

Lab 13-Mutiple Test Media

Material

Inoculating loop/needle

 SIM agar talls

 Wax pencil,

Bacterial cultures

Bunsen burne

Lighter

 Incubator

Kovac’s reagent.

Procedure

Triple Sugar Iron Agar

Each TSI test tube was labeled with student’s initials and the bacteria to be tested. Then the bacterial cultures were transferred aseptically using an inoculating needle and performed the stab-streak technique. To begin with, three-quarter of the tube to be bottom and center was stabbed. This was followed by inoculating the bottom of the tube.  Afterwards, the surface of the slant was inoculated in a zigzag motion using the tip of the needle.  The tubes were incubated at 37oC for 24 hours and the result recorded.

 Sulfur-Indole-Motility Media

Each SIM media tube was labeled properly with the specific bacteria being inoculated.  Then the bacterial culture was transferred to the tall aseptically.   A sterile need was stabbed down three-quarter of the tube and at the center. After which there was 24 hour incubation at 37oC. The sulfur and motility was observed on the second day.  Drops of Kovac’s solution were added to the top of the tall. A red/pink color change was examined if present and results recorded for Indole test.

Result

Lab 9

1. State the purpose of this lab.

To learn the different mechanisms involved in carbohydrate fermentation, hydrolysis of starch, understand methyl red and Voges-Proskauer reaction together with citrate utilization and how they are used in microorganism identification.

2.

Staphylococcus aureus

Escherichia coli

Enterobacter aerogenes

Bacillus subtilis

Micrococcus luteus

Phenol Red Glucose broth

Result

Observation

Yellow color.

No gas.

Positive for glucose ferment

Yellow color. Gas present.

Positive glucose ferment.

Yellow color. Gas present.

Positive for glucose ferment

Yellow color. No gas.

Positive glucose ferment.

Red. No gas.

Negative glucose ferment.

Phenol Red Sucrose broth

Observation

Result

Yellow color

Positive for sugar fermentation

Red

Negative for sugar fermentation

Yellow

Positive for sugar fermentation

Yellow

Positive for sucrose fermentation

Red color

Negative for sugar fermentation

Phenol Red Lactose broth

Observation

Result

Yellow

Positive lactose fermentation

Yellow

Positive lactose fermentation

Yellow

Positive lactose fermentation

Red

Negative lactose ferment

Red

Negative lactose ferment

Phenol Red Mannitol broth

Observation

Result

Yellow color

Positive Mannitol ferment

Yellow

Positive Mannitol ferment

Yellow

Positive Mannitol ferment

Orange

Positive for weak Mannitol ferment

Red

Negative Mannitol ferment

Starch agar plate

Observation

 Result

No color halo

Negative starch hydrolysis

No color halo

Negative starch hydrolysis

No halo

Negative starch hydrolysis

Halo

Positive starch hydrolysis

No clear halo

Negative starch hydrolysis

3. Why are positive results for MR and VP test seldom seen with the same organism (species)? Explain using the metabolic pathways the organisms use and the end products of each test.

It can be used to test the production of acetoin products. The pathway involves the formation of pyruvate from either dextrose or glucose using different metabolic pathways.  The process can result in production of unstable acidic compounds that are immediately converted to neutral products. Compounds such as acetoin are produced through butylene pathway while acidic compounds such as acetic and lactic are produced through the mixed acid pathway

4. Escherichia coli is a common bacteria found in the large intestine of the gastrointestinal system. People who are lactose intolerant are not able to break down lactose, because they are not producing the enzymes to do so. Using what you know from your test results, explain why this bacterium can contribute to some of the symptoms of lactose intolerance (outside research required).

Escherichia coli can contribute to the manifestation of lactose intolerance symptoms by inhibiting lactose conversion. Lactose is the main product carbohydrate found in milk. When it arrives in the intestine, lactase enzyme converts lactose into glucose and galactose which facilitates easy absorption y the colon (Lule et al. 43). However, the presence of these bacteria can interfere with the process of breaking down the lactose. The bacteria break down the lactose in the intestine which eventually results in excess gases in the stomach. In addition, there is large amount of liquid passing into the large intestine which makes it difficult to be absorbed by the colon. Therefore, the excess gas and fluid causes discomfort. A person can experience flatulence and diarrhea.

5a.What is a pH indicator? Why is it an important differential addition/tool added to the media?

The pH indicators are halochromic substances that are added to solution to detect a slight change in the pH of the solution and change color to help in visual recognition. It is an important differential tool added in the media because it helps in differentiation and isolation of organism based on metabolic and physiologic characteristics.

5b. Pick one of the media used in this experiment and explain the pH indicator used and how it works.

In the MR-VP culture media, the methyl red indicator is used to observe if the fermentation process is taking place through color changes.  The indicator remains red in a pH of 4.4 and below while it turns yellow in a pH of 6.2 and above. This is used to detect if the end product is acidic or basic.

10-Selective and Differential Media Results

1. State the purpose of this lab.

2.

Escherichia coli

(Gram negative)

Staphylococcus aureus(Gram positive)

Micrococcus luteus(Gram negative)

Proteus vulgaris( Gram negative)

Tryptic Soy Agar

Observation

Growth

Growth

Growth

Growth

Phenylethanol Agar

Observation

 Result

Yellow

Good growth

White

Good growth

Dark

Good growth

Yellow

Good growth

Mannitol Salt Agar

Observation

Results

Yellow

Negative for Mannitol fermentation

Yellow

Halo tolerant

Poor growth

Non halo tolerant

No growth

Inhibited by NaCl

Levine EMB Agar Observation

Result

Growth

Positive

Heavy lactose fermentation.

Abundant acid production

No growth

Inhibited by color and methylene blue dyes

No growth

Inhibited by eosin and methylene blue

Growth

Positive resists dyes

Pink/ light purple.

Possible coliform.

Slow lactose fermentation

Little acid production

Blood Agar Observation

Results

Blown green

Positive Alpha

Clear halo

Positive Beta

Brown green

Positive Alpha

Brown green halo

Positive Alpha

Columbia CNA observations

Results

No growth(NG)

Inhibited of Antibiotics

Gram negative

Clear halo

Positive growth

Resists antibiotics

Beta

Digestion

Gram positive

Positive growth

No color change

Gamma resistant to antibiotics Gram positive

No growth

Inhibited by Antibiotics Gram negative

Hektoen Enteric Agar

Observation

Results

Irresistible

Positive Orange

W/halo

Positive lactose and Positive fermentation 

Weak growth

Inhibited by salts

Weak growth inhibited by salts

Positive yellow/orange

Colonies/ no halo

Positive lactose fermentation

Negative Salicin fermentation

3. Which media used in this experiment are considered:

a. General Purpose:________TSA______________________________________________________

b. ONLY Selective:_______________PEA_______________________________________________

c. ONLY Differential:_________Sheep’s Blood Agar______________________________

d. BOTH Selective and Differential:___________MSA___CNA_________________

4a. Describe the why EMB, Hektoen Enteric and Mannitol Salt agar are selective. Include specific selective ingredients added to each media and what organisms these media select for and against.

MSA is considered selective because of the presence of Sodium chloride salt at 7.5 %. The salt facilitates the growth of specific organisms awhile inhibiting others. MSA is selective for staphylococcus aureus. Eosin Methylene Blue is considered selective because it contains Eosin Y and methylene blue which prevent the growth of gram positive bacteria. Hektoen Enteric contains bile salt as the selective agent promotes growth of only gram negative bacteria.

4b. Describe why EMB, Hektoen Enteric and Mannitol Salt agar are differential. Include specific differential ingredients added to each media and which types of organisms produce positive differential results.

EMB is considered to be differential because the media contains lactose and sucrose. They promote growth of coliform. They used on detecting the lactose fermentation therefore making EMB media differential of lactose ferment. MSA differential ingredients are sugar Mannitol and phenol red. Acid is released when the sugar is broken down resulting in pH change. Therefore, the pH indicator turns to yellow. MSA is able to differentiate non-pathogenic and pathogenic staphylococci such S aureus. Hektoen Enteric is differential because it can distinguish between pathogens and conical specimens. It can be used to differentiate Salmonella

and Shigella species from other gram- negative rods. The differential agents include bromthymol blue and acid fuschin used as pH indicators. On the other hand, sodium thiosulfate and ferric ammonium citrate are used test sulfide.

5. Urinary tract infections are commonly caused by Escherichia coli. Choose one of the media used in this lab that can isolate and identify this bacterium from a urine sample (which may contain many types of organisms). Explain why you chose this media and the observations/results this organism will show.

The suitable media to be used is Blood Agar media because it contains enough nutrients to support the growth of different organisms.  The result is likely to be positive because the media supported their growth.

6. Strep throat is caused by infection with Streptococcus pyogenes, which is Gram positive. Choose one of the media used in this lab that can isolate and identify this bacterium from a throat (which may contain many types of organisms). Explain why you chose this media and the observations/results this organism may show.

Blood Agar is one of media that can be used in the identification of S. pyogenes in the laboratory. It is the selected for identification because it is a rich nutrient differential media that can be used to detect hemolysis as a result of gram positive bacteria toxins.  Possible results include a clear zone around the bacteria culture which indicates that hemolysis took place. Partial hemolysis is shown by a greenish zone. No significant change around the bacteria growth in blood shows that the red blood cells were not hemolyzed.

11-Physiological Characteristics of Bacteria: Nitrogen Metabolism

Organism

Enterobacter aerogenes(Gram negative)

Proteus vulgaris(Gram negative)

Micrococcus luteus( Gram positive)

Pseudomonas aeruginosa(Gram negative)

Unknown #24

Gelatin Deep

Observation

Results

Solid media

gelatin hydrolysis is negative

Liquid media

gelatin hydrolysis

is Positive

Liquid media

gelatin hydrolysis is Positive

Slightly liquid( weak media)

Positive gelatin hydrolysis

Liquid media

Weak positive gelatin hydrolysis

Tryptone Broth

Observations

Results

 Yellow ring

Negative Indole production

Pink ring

Positive Indole production

Yellow/green ring

Negative Indole production

Yellow/green ring

Negative  Indole production

Yellow/green ring

Negative Indole production

Peptone Iron Agar Deep

Observations

Results

No black precipitate

Negative H2S gas production

Black precipitate

Positive H2S gas production

No black precipitate

Negative for H2S gas production

No black precipitate

Negative H2S gas production

No black precipitate

Negative H2S Gas production

Urea broth

Observations

Results

Orange media

Negative Urea hydrolysis

Pink media

Positive Urea hydrolysis

Orange weak

Positive Urea hydrolysis

Orange color

Negative Urea hydrolysis

Orange media

Negative Urea hydrolysis

Nitrate Broth

Observation(Both steps if needed)

Results(Both steps if needed)

Red media after step 1

Positive nitrite /nitrate reduction

Red media after A/B nitrate

Positive nitrate reduction

First step no color change

Negative nitrite

Second step: Red color

Positive nitrite/nitrate reduction

No color change for step one

Second step: No color change yellow

Negative for nitrite

Positive for denitrification

 Red media after Nitrate A and B

Positive for  nitrite/ Nitrate reduction

1. What is hydrolysis and why is it used by bacteria? Describe an example hydrolysis reaction that we are testing for in this lab.

Hydrolysis in living organism is where water is added into a molecule to break it.  It is used by bacteria that have enzymes such as cellulases to break down cellulose.

2. If your bacteria form a black precipitate in peptone iron agar, what does this indicate? Please discuss the metabolic ability of the organism and the differential reaction in this media.

The formation of a black precipitate is an indication that hydrogen sulfide gas was produced and reacted with iron sulfide. This means sulfur production occurred in in an acidic environment which promoted the fermentation of a substance

3. Describe the two reasons gelatin is not used as a solidifying agent for biological media. What is used as a solidifying agent in media and why?

Gelatin is not used as a solidifying agent because despite being solid at room temperature, it has a relative low melting point of less than 35oC which makes it unsuitable. The second reason is that gelatin can easily be ingested by bacteria. Agar is the one used as a solidifying media because it is not easily digested by most bacteria and it has a high melting point.

4.  Explain why when changing a baby’s diaper there is often an ammonia smell. Consider the normal flora of the baby’s intestinal system and how they can contribute to this smell.

The ammonium smell can originate from the bacteria action of the baby’s feces that hydrolyzes urea.

5. In the nitrate reduction test you add Nitrite A and B to your tube and get no color change. Explain the possible metabolic pathways the organism may have used and the next step needed to complete the test. What does this step confirm

The process of nitrate reduction to nitrite is an aerobic respiration.  If there is no color change after the addition of Nitrite A and Nitrite B, then it means that the nitrite was not reduced or the organism denitrified the nitrate to ammonia.  Another step that involves the addition of zinc dust is meant to confirm the presence of nitrate in the solution.

Lab 12 Results-Physiological Characteristics: Miscellaneous Reactions

Enterobacter aerogenes(Gram negative)

Pseudomonas aeruginosa( Gram negative)

B  cereus( Gram positive)

Staphylococcus aureus(Gram positive)

Unknown #24

Catalase Test

Observation

Results

Bubbles

Positive catalase

Bubbles

Positive catalase

Bubbles

Positive for oxidase

Yellow/brown

Negative catalase

Bubbles

Weak  for positive catalase

Oxidase Test

Observation

Results

Dark purple

Positive for oxidase

Dark purple

Positive for oxidase

Dark purple

Positive for oxidase

Yellow/brown

Positive for oxidase

Dark purple

Positive for oxidase

 Dnase Media

Observation

Result

No clear halo

Negative for  DNA hydrolysis

No clear halo

Negative for DNA hydrolysis

Clear halo

Positive DNA hydrolysis

Slight clear  halo

Weak positive DNA hydrolysis

No clear halo

Negative DNA hydrolysis

Bile Esculin Media

Observations

Results

Growth

Black Precipitate

Positive esculin hydrolysis

Growth

No Black precipitate

Negative esculin hydrolysis

Growth no  black precipitate

Negative for esculin hydrolysis

Growth with no black precipitate

Negative for esculin hydrolysis

Growth black precipitate

Positive esculin hydrolysis

Motility Media

Observation

Results

Growth away from  stab line

Positive motility

Growth away  from stab line

Positive motility

Growth along stab line

Negative motility

Growth along stab line

Negative motility

Growth away from stab line

Positive motility

3. What is the medical significance of DNase? How does this enzyme contribute to pathogenicity of the bacteria?

DNase medical significance is viewed when the DNase agar is used to test the presence of bacteria by through an indicator. DNase enzymes help the bacteria to breakdown and neutralize foreign molecules that are attacking it. 

4. What happens to hydrogen peroxide when it comes in contact with catalase? Why should you never use hydrogen peroxide on an open wound?

When hydrogen peroxide comes into contact with catalase, bubbles and foam develops as a result of catalase enzyme breaking down the hydrogen peroxide into water and oxygen. Hydrogen peroxide should never be used on open wounds because when it is added to the tissue, it attacks bacteria and at the same time reacts with enzyme catalase in the body tissues. This results in destroying healthy cells that contain enzyme catalase which will interfere with the healing process.

5. Obligate anaerobes typically do not contain or used catalase. Please explain why.

 The reason for the absence of catalase in obligate anaerobes is because catalase enzyme reaction with hydrogen is oxygen and water. Their habitat is free of oxygen therefore do not require catalase to facilitate the con