The mid of the nineteenth century witnessed an ever growing interest in the pivotal role of
microorganisms in carrying out not only the various processes related to fermentations but also tackling
some of the human diseases. Nevertheless, Pasteur’s articulated contributions on fermentation evidently
proved and established that microorganisms in particular may cater as highly specific entities in performing
a host of chemical transformations.
Winogradsky and Beijerinck legitimately shared the overall merit and credibility for establishing
the precise role of microbes in the critical transformations of N and S.
Windogradsky (1856-1953) : He critically examined and observed that there exist a plethora of
distinct and discrete categories of microorganisms each of which is invariably characterized by its inherent
capability to make use of a specific inorganic energy source.
Examples :
(a) Sulphur Microbes : They oxidize inorganic sulphur containing entities exclusively.
(b) Nitrogen Microbes : They oxidize inorganic nitrogen containing compounds solely.
Interestingly, Winogradsky caused to be seen that there are certain microorganisms which either
in association with free living or higher plants may exclusively make use of gaseous nitrogen for the
synthesis of the specific cell components.
Hellriegel and Wilfarth (1888) : They showed explicitely that a predominantly mutual and
immensely useful symbiosis does exist between bacteria and the leguminous plants particularly.
Beijerinck (1901) : He meticulously observed, described, and even enumerated the usefulness
of the very presence of the ‘free-living nitrogen fixing’ organism Azotobacter** in maintaining the
fertility of the soil.
EmoticonEmoticon