Agricultural microbiology deals with microbes associated with plants and soils. Soil microbiology studies microorganisms in soil and their functions. Sergei Winogradsky discovered biogeochemical cycles and isolated different bacteria with abilities like nitrogen fixation or converting sulfur. Martinus Beijerinck developed enrichment media, isolated free-living nitrogen-fixing bacteria, and explained symbiotic relationships between bacteria and plants. Developments in plant pathology include the first scientific records of relationships between bacteria and plant diseases, discoveries of viral transmission through grafting and filters, and explanations of diseases transmitted by insects and caused by bacterial toxins.

1. Developments in Agriculture
Microbiology
By: Dr. MohammedAzim Bagban

2. Agricultural microbiology
• Agricultural microbiology is a branch of
microbiology dealing with plant-associated
microbes and plant and animal diseases. It
also deals with the microbiology of soil
fertility, such as microbial degradation of
organic matter and soil nutrient
transformations.

3. Soil microbiology
• Soil microbiology is the study of microorganisms in
soil, their functions, and how they affect soil
properties. It is believed that between two and four
billion years ago, the first ancient bacteria and
microorganisms came about on Earth's oceans.
• These bacteria could fix nitrogen, in time multiplied,
and as a result released oxygen into the atmosphere.
• This led to more advanced microorganisms, which are
important because they affect soil structure and
fertility. Soil microorganisms can be classified as
bacteria, actinomycetes, fungi, algae and protozoa.
• Each of these groups has characteristics that define
them and their functions in soil.

4. Development in Soil Microbiology
• Sergei Winogradsky:
• He was a Russian
microbiologist, ecologist and
soil scientist who pioneered
the cycle-of-life concept.
• Winogradsky discovered
various biogeochemical
cycles and parts of these
cycles.

5. • Sergei Winogradsky have isolated different
types of bacteria from soil having different
abilities.
• Some bacteria are chemoautotrophic. They
grow only on inorganic substances and CO2

6. Some bacteria were doing nitrogen
fixation for plants. e.g. Azatobactor,
Rhizobium

7. Some bacteria could covert sulfur and
other compounds. E.g. Green sulfur
bacteria

8. Martinus Beijerinck
Martinus Willem Beijerinck (16 March
1851 – 1 January 1931) was a Dutch
microbiologist and botanist. He is
often considered one of the founders
of virology and environmental
microbiology.

9. Martinus Beijerinck
• Development of Enrichment culture media as
he isolated cellulose digesting bacteria.
• He isolated free living nitrogen fixing bacteria
belonging to Beijerinckia.
• He explained the symbiotic relationship of
bacteria and plants specially in Rhizobium and
leguminous plants.

10. Developments in Plant pathology
• Plant pathology (also phytopathology) is the
scientific study of diseases in plants caused by
pathogens (infectious organisms)
• First scientific record of relationship between
bacteria and apple & pears was made by Burill
in 1878.
• Erwin Smith explained that plant disease can
be transmitted by budding or grafting.

11. • In 1894, Iwanowsky explained filter passing
agents responsible for Tobacco mosaic
disease.
• In 1898, Beijerinck Explained that causative
agent for mosaic disease are Virus.
• Hashimoto, A.B. Bell, A Adams, and J.C Shaw
explained viral diseases of plants transmitted
by insects. (e.g. Arthropod-borne plant
viruses).
• In 1969, Owen explained the role of bacterial
toxins and enzymes in production of
diseases.