Microbial growth

• 1.27 Be able to demonstrate an understanding of Louis Pasteur’s contribution to the development of aseptic techniques.
• 1.28 Revise any investigations on the conditions affecting growth of microorganisms (using resazurin dye).

Louis Pasteur (/ˈluːi pæˈstɜr/, French: [lwi pastœʁ]; December 27, 1822 – September 28, 1895) was a

French chemist and microbiologist renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurisation. 

He is remembered for his remarkable breakthroughs in the causes and preventions of diseases, and his discoveries have saved countless lives ever since. He reduced mortality from puerperal fever, and created the first vaccines for rabies and anthrax. His medical discoveries provided direct support for the germ theory of disease and its application in clinical medicine. He is best known to the general public for his invention of the technique of treating milk and wine to stop bacterial contamination, a process now called pasteurisation.

  

Pasteur was responsible for crushing the doctrine of spontaneous generation. He performed experiments that showed that without contamination, microorganisms could not develop. Under the auspices of the French Academy of Sciences, he demonstrated that in sterilized and sealed flasks nothing ever developed, and in sterilized but open flasks microorganism could grow. This experiment won him the Alhumbert Prize of the academy.

Spontaneous generation is an obsolete body of thought on the ordinary formation of living organisms without descent from similar organisms. Typically, the idea was that certain forms such as fleas could arise from inanimate matter such as dust, or that maggots could arise from dead flesh. In this case, Pasteur showed that microorganisms did not spontaneously 'appear' in the broth but in fact the broth needed to be contaminated in order for the microorganisms to grow. 

Aseptic technique is a procedure used by medical staff and scientists to prevent the spread of infection. The goal is to reach asepsis, which means an environment that is free of harmful microorganisms. 

If an unwelcome bacteria lands on a surface which provides conditions allow growth of the microorganisms, (warmth, moisture and a food source) it will divide by binary fission until the population grows so much that it runs out of resources or space. 

Using Resazurin to estimate the growth of Bacteria in Milk. 

You need to know how to investigate the growth of bacteria in milk. One way of doing this is to use a dye called resazurin. This can be added to milk kept at different temperatures to see the relative growth of bacteria.

Resazurin changes from blue to pink to white as the presence of bacteria increases. A quicker change in colour indicates the presence of more bacteria.