What are Microorganisms?

Photo Credit: Sara Wright

Microorganisms are groups of very small organisms for which the soil is the natural habitat, and which may include groups such as bacteria, fungi, protozoans, algae, and actinomycetes. The organisms play crucial roles in soil formation, soil structure, fertility, aeration, and drainage.

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Regional Educator ResourcesOther Educator ResourcesTechnical Resources
Title Source Resource type and Date Short Summary / Preview
Purdue Soil Health Education website Purdue Soil Health Education Website Video

Sep 2017

Dr. John Graveel, Purdue Agronomy Department discusses microbiology activity within soils.

The ABCs of Soil Health USDA NRCS Slideshow

not dated


Example: “M is for Microbes”, There are more MICROBES in one teaspoon of healthy soil than people on the Earth.

Understanding Soil Microbes and Nutrient Recycling Ohio State University Extension Webpage

Sep 2010


The role of microbes in nutrient cycling and soil health.

Microbes Crucial to Long-Term Soil Health Michigan State University Research summary



Summary of research on soil health and the role of microbes from the MSU Kellogg Biological Station Long-Term Ecological Research (LTER) program.

Soil Microorganisms SARE Extension Webpage



Microorganisms are very small forms of life that can sometimes live as single cells, although many also form colonies of cells.

The Science of Soil Health: Changing the Way we Think about Soil Microbes USDA NRCS Video

Feb 2014

Dr. Kristine Nichols, Soil Microbiologist, Agricultural Research Services, Mandan ND discusses soil microbes within the context of soil health – NRCS video.

The Science of Soil Health: Fighting Plant Disease with Microbes USDA NRCS Video

Jul 2014

Video series entitled “Unlock the Science of Soil Health” The Science of Soil Health: Fighting Plant Disease with Microbes featuring Dr. Geoff Zehnder, Professor of Entomology, Coordinator of IPM and Sustainable Agriculture, Clemson University.

PLFA video protocol JoVE from University of Wisconsin-Madison Researchers Video



This video protocol explains how phospholipid fatty acid analysis is done and how to interpret the data.

Title Source Resource type and date Short Summary
Building Healthy Soils University of Tennessee Extension Fact Sheet

Sep 2012


Many different types of organisms living in soils provide valuable services. Microorganisms, such as bacteria and fungi, support plant fertility by assisting with the release of minerals bound up in soil organic matter.

Title Source Resource type and Date Short Summary
The role of microarthropods in emerging models of soil organic matter Soil Biology and Biochemistry Peer-Reviewed Publication

Nov 2016


Research paper summarizing how microarthropods affect soil organic matter dynamics.

Evaluation of methods to estimate the soil microbial biomass and the relationship with soil texture and organic matter Soil Biology and Biochemistry Peer-Reviewed Publication

Jul 1992


Tested different methods to measure soil microbial biomass. Biomass and activity of the soil microflora were significantly related to clay, soil organic C and especially to total N content.

Soil health—a new challenge for microbiologists and chemists International Microbiology Peer-Reviewed Publication

Jan 2005


One of the key objectives in determining soil health is to acquire indicators that can be used to evaluate the soil’s current status and hence to develop sustainable agricultural systems. In this regard, significant progress has been made over the last few years in the development of specific bio-markers and macromolecular probes, enabling rapid and reliable measurements of soil microbial communities.

Microorganisms:, Global Soil Biodiversity Atlas ePublications Office of the European Union Book

May 2016

Soil biodiversity is crucial to soil health and microorganisms play a role in that biodiversity.
Importance of Soil Temperature for the Growth of Temperate Crops under a Tropical Climate and Functional Role of Soil Microbial Diversity Microbes and Environments Peer-Reviewed Publication

Apr 2018


Soil temperature closely correlates with the growth of temperate crops, and affects plant processes and soil microbial diversity. The present study focuses on the effects of soil temperatures on lettuce growth and soil microbial diversity that maintains the growth of lettuce at low soil temperatures.

Microbial Biomass C, N Michigan State University, LTER Extension / Research Protocol

Not Dated


Protocol to measure microbial biomass in the soil.

Equations for Soil Microbial Biovolume and Carbon Calculation Michigan State University, LTER Extension / Research Protocol

Not Dated


The equations for calculation of soil microbial biovolume and carbon are specified.

This page reviewed by Liz Schultheis.

Last reviewed 10/24/19