• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10

The aim of this investigation is to investigate how changing the temperature affects growth and survival of bacteria. The bacterium's Escherichia coli, Bacillus stearothermophilus, Bacillus subtilis, Pseudomonas fluorescens and Enterococcus

Extracts from this document...


Student: N009834 The Effect of Heat on Growth and Survival of Bacteria Abstract The aim of this investigation is to investigate how changing the temperature affects growth and survival of bacteria. The bacterium's Escherichia coli, Bacillus stearothermophilus, Bacillus subtilis, Pseudomonas fluorescens and Enterococcus faecalis will be investigated. Each of the bacteria were loop inoculated into glucose nutrient broths, then incubated at five different temperatures, 4OC, 25OC, 37OC, 45OC and 55OC for seven days to see where growth, if any has occurred at which particular temperature. Results showed that bacterium Pseudomonas fluorescens grew best at the lower temperatures and Bacillus subtilis grew paramount at the higher temperatures. Another experiment was carried out where the aim of the investigation was to show the relationship between the temperature and the time to kill for a number of species of bacteria. Each of the bacterium's nutrient broth bottles were placed in four waterbaths at 40OC, 60OC, 80OC and 100OC. Each bottle was then removed one by one at 0, 2, 5, 30 and 90 minutes, then incubated for seven days. Bacillus stearothermophilus broths were incubated at 55OC. Escherichia coli and Enterococcus faecalis broths were incubated at 37OC. Bacillus subtilis and Pseudomonas fluorescens broths were incubated at 30OC. ...read more.


Psychrophiles have largely unsaturated fatty acids in their plasma membranes which makes them adapted to their environment. 'The degree of unsaturation of a fatty acid correlates with its solidification temperature or thermal transition stage (i.e., the temperature at which the lipid melts or solidifies); unsaturated fatty acids remain liquid at low temperature but are also denatured at moderate temperature'. www2. Within the membrane of the Thermophiles are saturated fatty acids which are stable at high temperatures; however they too solidify at relatively high temperatures. The fluidity of the membrane is affected by the fatty acids in the membrane, whether they are solid or liquid, this affects its ability to function. Enzymes are contained within Psychrophiles which continue functioning although at condensed rate, near temperatures of 0O. Psycrophile proteins/membranes adapt to low temperatures, but at 37OC (body temperature of warm blooded animals) they do not function. Thermophiles are adapted to their function of temperatures over 60OC in a number of ways. They have a high Cytosine and Guanine content in their DNA which is at least as high as the optimum temperature for the organisms' growth. 'But this is not always the case, and the correlation is far from perfect, so thermophile DNA must be stabilized in these cells by other means. ...read more.


No growth at the highest temperature but very faint growth shown at 4oC. Discussion As you can see from the results of the experiment, the five different bacterium's can now be categorised into psychrophiles, mesophiles and thermophiles. Escherichia coli appears to be a mesophile as it grows in moderate temperatures, growing greatest at human body temperature of 37oC, indicating that this organism is obviously present within our human bodies. Bacillus stearothermophilus appears to be a thermophile but also is able to grow in mesophile conditions. There was very faint growth at 55oC indicating that if the temperature had increased further, more growth will have occurred. Bacillus subtilis also appears as a mesophile as it grows greatest within moderate temperatures of 37oC and 45oC, yet fails to grow at extreme temperatures of 55oC and faintly at low temperatures. The only psychrophile from these five bacterium's is Pseudomonas fluorescens as this grows very heavily at low temperatures of 4oC and 25oC, yet faintly and none at when the temperature increases to 37oC and above. Finally another mesophile is the Enterococcus faecalis as this also grows best at 37oC and at moderate temperatures it showed medium growth. It showed very little growth at 4oC and no growth at the extreme of 55oC. Results The effect of heat on survival of bacteria The following tables indicate the effect of heat on the survival of the five different bacterium's. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Living Things in their Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Living Things in their Environment essays

  1. Marked by a teacher

    Escherichia coli and antibiotic resistanceIntroduction:Escherichia coli, short E. coli is an important bacteria that ...

    5 star(s)

    A native organic population, whether be E. coli bacteria or insects is most susceptible to the new a type of foreign invasion because the organic population has previous experience with the new force and thus has no defense against it.

  2. Marked by a teacher

    The effects of disinfectants and antibacterial soap on bacterial growth

    5 star(s)

    the bacteria was incubated at 37' C, which probably encouraged the bacteria found on skin more than the bacteria found on inanimate surfaces because it is closer to body temperature than to room temperature. Later, when regrowing the bacteria front our culture tubes, we incubated the plates at 320 C because 37' C had melted our agar.

  1. Marked by a teacher

    A2 Biology Coursework -Investigation into the effect of different concentrations of antibiotics on the ...

    4 star(s)

    Replace the lid and refasten the lid with cello tape 27. Place this dish in an incubator at 25 degrees for 15 minutes. 28. Repeat procedures 25 to 27 for the other dishes. 29. After 15 minutes is over get a Petri dish and open the lid by cutting

  2. Marked by a teacher

    In this experiment, mung bean seedlings and Brine shrimp eggs were used to study ...

    4 star(s)

    The different salinity of water solution is prepared by using sodium chloride dissolving in mineral water. Sodium chloride is easily available as common salt. Mineral water is used as the Brine shrimp is very sensitive to microbes. 1% salt solution is used to examine the effect of temperature on the

  1. Marked by a teacher

    An Investigation into a Woodlice's Preferred Choice of Environment.

    3 star(s)

    Seeing as I expected there to be no difference n where the woodlice would go, my expected number is 10, meaning that there would 10 in each condition at all times. In order to get the observed for each condition, I worked out the overall average and am using that in my test.

  2. This assignment is about planning and designing practical experiment to carry out an investigation ...

    C 2.9 2.75 2.85 E 4.10 4.70 4.40 FC 3.40 3.35 3.37 MT 1.65 1.15 1.40 PG 0.00 0.00 0.00 S 4.10 4.30 4.20 T 4.50 4.00 4.25 NO 3.45 3.50 3.47 Results/implementing In the practical, I used a ruler to measure the diameter of area of no growth for each dish (plate)

  1. Using the streak plate method, compare the effect of two different brands of toothpaste ...

    In the gram-negative bacteria the peptidoglycan is much thinner with only 15-20% of the cell wall being made up of peptidoglycan and this is only intermittently cross-linked. Here are two diagrams of the gram bacteria showing there structure and contents: As seen in the above diagrams, the gram-negative bacteria are

  2. An investigation into the antibiotic effects of penicillin and streptomycin on the bacterium Escherichia ...

    out in microbiology to classify a bacterium into one of two groups: Gram-positive or Gram-negative. It was developed by Hans Christian Gram, a Danish physician, in 1884. The bacteria that stain purple after treatment are Gram-positive, and those that stain red are Gram-negative.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work