History of Soil Microbiology (1600 – 1920)
There is enough evidence in the literature to believe that microorganisms were the earliest of the living things that existed on this planet. Man depends on crop plants for his existence and crop plants in turn depend on soil and soil microorganisms for their nutrition. Scientists form the beginning studied the microorganisms from water, air, soil etc. and recognized the role of microorganisms in natural processes and realized the importance of soil microorganisms in growth and development of plants.
Thus, we see that microorganisms have been playing a significant role long before they were discovered by man. Today, soil is considered to be the main source of scavenging the organic wastes through microbial action and is also a rich store house for industrial micro flora of great economic importance.
Unlike soil science whose origin can be traced back to Roman & Aryan times, soil microbiology is emerged as a distinct branch of soil science during first half of the 19th century. Some of the notable contributions made by several scientists in field of soil microbiology are highlighted in the following paragraphs.
A. V. Leeuwenhock (1673) discovered and described microorganisms through his own made first simple microscope with magnification of 200 to 300 times. He observed minute, moving objects which he called “animalcules" (small animals) which are now known as protozoa, fungi and bacteria. He for the first time made the authentic drawings of microorganisms (protozoa, bacteria, fungi).
Robert Hook (1635-1703) developed a compound microscope with multiple lenses and described the fascinating world of the microbes.
J. B. Boussingault (1838) showed that leguminous plants can fix atmospheric nitrogen and increase nitrogen content in the soil.
J. Von Liebig (1856) showed that nitrates were formed in soil due to addition of nitrogenous fertilizers in soil.
S. N. Winogradsky discovered the autotrophic mode of life among bacteria and established the microbiological transformation of nitrogen and sulphur. Isolated for the first time nitrifying bacteria and demonstrated role of these bacteria in nitrification (l890), further he demonstrated that free-living Clostridium pasteuriamum could fix atmospheric nitrogen (1893). Therefore, he is considered as "Father of soil microbiology".
W. B. Leismaan (1858) and M. S. Woronin (1866) demonstrated that root nodules in legumes were formed by a specific group of bacteria.
Jodin (1862, France) gave the first experimental evidence of elemental nitrogen fixation by microorganisms.
Robert Koch (1882) developed gelatin plate/ streak plate technique for isolation of specific type of bacteria in soil, formulated Koch’s postulates to establish causal relationship between host – pathogen and disease.
R. Warington (1878) showed that nitrification in soil was a microbial process.
B. Frank i) discovered (1880) an actinomycetes “Frankia” (Actinorhizal symbiosis) inducing root nodules in non-legumes tress of genera Alnus sp and Casurina growing in temperate forests, ii) coined (1885) the term " Mycorrhiza" to denote association of certain fungal symbionts with plant roots (Mycorrhiza-A symbiotic association between a fungus and roots of higher plants. Renamed the genus Bacillus as Rhizobium (1889).
H. Hellriegel and H. Wilfarth (1886) showed that the growth of non-legume plant was directly proportional to the amount of nitrogen supplied, whereas, in legumes there was no relationship between the quantity of nitrogen supplied and extent of plant growth. They also suggested that bacteria in the root nodules of legumes accumulate atmospheric nitrogen and made it available to plants. Showed that a mutually beneficial association exists between bacteria (Rhizobia) and legume root and legumes could utilize atmospheric nitrogen (1988).
M. W. Beijerinck (1888) isolated root nodule bacteria in pure culture from nodules in legumes and named them as Bacillus radicola Considered as father of "Microbial ecology". He was the first Director of the Delft School of microbiology (Netherland).
Beijerinck and Winogradsky (1890) developed the enrichment culture technique for isolation of soil organisms, proved independently that transformation of nitrogen in nature is largely due to the activities of various groups of soil microorganisms (1891). Therefore, they are considered as "Pioneer’s in soil bacteriology”.
S. N. Winogadsky (1891) demonstrated the role of bacteria in nitrification and further in fill 1983 demonstrated that free living Clostridium pasteurianum could fix atmospheric nitrogen.
Omeliansky (1902) found the anaerobic degradation of cellulose by soil bacteria.
J. G. Lipman and P. E. Brown (1903, USA) studied ammonification of organic nitrogenous substances by soil microorganisms and developed the Tumbler or Beaker for studying different types of transformation in soil.
Hiltner (Germany, 1904) coined the term "Rhizosphere" to denote that region of soil which is subjected to the influence of plant roots. Rhizosphere is the region where soil
and plant roots make contact.
Russel and Hutchinson (1909, England), proved the importance of protozoa controlling/ maintaining bacterial population and their activity in soil.
Conn (1918) developed “Direct soil examination” technique for studying soil microorganisms.
Rayner (192I) and Melin (1927) carried out the intensive study on Mycorrhiza.