Microbes in Human Welfare
Introduction
Besides macroscopic plants and animals, microbes are the major components of biological systems on this earth
You have studied about the diversity of living organisms in Class XI
Microbes are diverse– protozoa, bacteria, fungi and microscopic animal and plant viruses, viroids and also prions that are proteinacious infectious agents
Some of the microbes are shown in Figures 8.1 and 8.2.
Such cultures are useful in studies on micro-organisms
In chapter 8, you have read that microbes cause a large number of diseases in human beings
They also cause diseases in animals and plants
But this should not make you think that all microbes are harmful; several microbes are useful to man in diverse ways
Some of the most important contributions of microbes to human welfare are discussed in this chapter
Microbes in Household Products
You would be surprised to know that we use microbes or products derived from them everyday
A common example is the production of curd from milk
Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd
During growth, the LAB produce acids that coagulate and partially digest the milk proteins
A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12
In our stomach too, the LAB play very beneficial role in checking diseasecausing microbes
The dough, which is used for making foods such as dosa and idli is also fermented by bacteria
The puffed-up appearance of dough is due to the production of CO2 gas
Can you tell which metabolic pathway is taking place resulting in the formation of CO2? Where do you think the bacteria for these fermentations come from? Similarly the dough, which is used for making bread, is fermented using baker’s yeast (Saccharomyces cerevisiae)
A number of traditional drinks and foods are also made by fermentation by the microbes
‘Toddy’, a traditional drink of some parts of southern India is made by fermenting sap from palms
Microbes are also used to ferment fish, soyabean and bambooshoots to make foods
Cheese, is one of the oldest food items in which microbes were used
Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbes used
For example, the large holes in ‘Swiss cheese’ are due to production of a large amount of CO 2 by a bacterium named Propionibacterium sharmanii