GOLDEN ERA OF MICROBIOLOGY

Golden era of microbiology started with the work of Louis Pasteur(France)and Robert Koch(Germany). Louis Pasteur(1822-1895) investigated number nuber of aspects such as he showed that boiled medium could remain clear in a swan-neck flask,open to the air through a sinuous horizontal tube in which dust particles would settle as air reentered the cooling vessel.Pasteur also demostrated that in the relatively dust free atmosphere of a quite cellar,or of a mountain top, sealed flasks could be opened and then released so as to avoid contamination.

Pasteur delivered a lecture in 1864 at Sorbonne and made sensation by discovering life  is a germ and germ is a life. F.Cohn(1876)studied the biology of bacilli. John Tyndal(1820-1893)shoowed thhe hay had committed his lab with an incredible kind of living organism. Ferdinand John(1877)demonstrated the resistant forms as small, refractile endospores, a special stage in the life cycle of hay bacillus(Bacillus subtilis).Since spores are readily sterilized in the presence of moisture(at 120degree celcius),the autoclave,which uses steam under pressure,became hallmark of the bacteriology. 

Pasteur(1857) became interested in fermentation products and observed different kind of microbes associated with different kind of fermentation:spheres of variable size(yeast cells)in the alcoholic fermentation,and smaller rods(lactobacilli)in the lactic acid fermentation.During this experiment,Pasteur established the study of microbial metabolism and in particular he showed that life is possible without air.Pasteur explained that in grape juice the high sugar concentration and the low protien content(i.e.low buffering power)lead to a low pH,which allows the outgrowth of acid-resistant yeasts and thus yields an alcoholic fermentation.In milk,in contrast,the much higher protien and lower sugar content favour the outgrowth of fast growing but more acid-sensitive bacteria,which cause a lactic acid fermentation.This finding led Pasteur to state that specific microbes might also be causes of specific disease in man.

Pasteur developed the procedure of gentle heating(i.e.pasteurization)to prevent the spoilage of beer and wine by undesired microbes.This process was later used to prevent milk borne diseases of man.Of the great economic importance was the extention of industrial fermentations from the production of foods and beverages to that of valuable chemicals,such as glycerol,acetone,and later vitamins,antibiotics and alkaloids.

The unity of biology at a molecular level concept was developed when it was discovered that the carbohydrate metabolism pathways are similar in some microbes and in mammals.This discovery was made towards the end of the Pasteurization era notably by Winogradsky in Russia and Beijerinck in Holland who discovered variety of metabolic patterns by different kinds of bacteria adapted to different ecological niches.

The ecological niche is defined as 'the physical space occupied by an organism,but also its functional role in the communnity'.These organisms were isolated by using Pasteur's principle of selective cultivation:enrichment culture in which only a particular energy source is provided,and growth is restricted to those organisms that can use that source.