Soil Quality Laboratory
The Soil Environment
Selman Waksman’s Seven Grand Questions on Soil Microbiology
Selman Waksman, a biochemist and soil microbiologist whose research into the decomposition of organisms that live in soil, co-discovered streptomycin along with Albert Schatz and Elizabeth Bugie. Waksman’s team in the Rutgers Department of Biochemistry and Microbiology. discovered several antibiotics, including actinomycin, clavacin, streptothricin, streptomycin, grisein, neomycin, fradicin, candicidin, candidin. Streptomycin was the first effective drug against gram-negative bacteria and the first antibiotic used to cure tuberculosis. In 1952, Waksman was awarded the Nobel Prize in Physiology or Medicine for “ingenious, systematic, and successful studies of the soil microbes that led to the discovery of streptomycin.” {NOTE: There are indeed controversies about exactly WHO deserves what share of the credit for the discovery of streptomycin, but there is NO controversy whatsoever that this work happened in Waksman’s lab and that the members of lab developed and refined the procedures for the ingenious, systematic, and successful studies of the soil microbes.}
It is precisely that ingenious, systematic, and successful studies of the soil microbes that we are interested in carrying forward with Soil Quality Laboratory. Although Waksman’s research was more general and far reaching because his lab also examined the role of bacteria in marine systems, with a particular focus on the role of bacteria in nutrient cycles, we are particularly interested in SOIL science and especially SOIL microbiology … which is why we are still very much interested in the Seven Grand Questions that Waksman posed in his 1927 book, Principles of Soil Microbiology
What organisms are active under field conditions and in what ways?
Soil is a complex ecosystem that hosts a diverse array of organisms, many of which are active under field conditions. These organisms play crucial roles in maintaining soil health, fertility, and structure. Here are some of the key soil organisms and their activities:
- Bacteria:
- Decompose organic matter, releasing nutrients for plant uptake
- Symbiotic relationships with plants, colonizing their roots, transforming function, helping with nutriet cycling, improving stress tolerance, protect against pathogens and promoting growth such as the gram-negative bacteria rhizobium’s ability to fix atmospheric nitrogen.
- Improving soil structure and aggregation by producing extracellular polysaccharides and other compounds that bind soil particles together.
- Bioremediation: Certain species of bacteria are capable of [just as certain species of fungi also are capable of] degrading pollutants and toxic compounds in the soil, such as pesticides, hydrocarbons, and heavy metals.
- Actinomycetes are an especially noteworthy group of gram-positive, filamentous bacteria, ubiquitous in soil environments and decaying organic material, possessing a wide array of enzymes that enable them to break down complex organic compounds, such as lignin, chitin, and cellulose and known for their ability to produce a wide range of bioactive compounds, such as streptomycin and streptothicin, actinomycin, tetracyclines, erythromycin, rapamcyin, vancomycin, chloramphenicol, kanamycin, cephalosporins, rifamycin, daptomycin
- Fungi:
- Decompose complex organic compounds, such as lignin and cellulose
- Form symbiotic relationships with plant roots (mycorrhizae), enhancing nutrient and water uptake
- Help in soil aggregation and structure formation
- Certain species of fungi are capable of degrading pollutants and toxic compounds in the soil, such as pesticides, hydrocarbons, and heavy metals. Several species of fungi found in soils have been identified as potential agents for bioremediation due to their ability to degrade pollutants and toxic compounds. These fungi possess enzymatic systems that allow them to break down complex and recalcitrant molecules. Examples include: basidiomycetes species (white rot fungi), aspergillus and penicillium species, trichoderma species, fusarium species, arbuscular mycorrhizal fungi (AMF).
- Protozoa:
- Feed on bacteria, releasing nutrients in plant-available forms
- Regulate bacterial populations
- Contribute to nutrient cycling
- Nematodes:
- Feed on bacteria, fungi, and other soil organisms
- Help in nutrient mineralization and cycling
- Some species are plant parasites, while others are beneficial predators
- Earthworms:
- Improve soil structure and aeration through burrowing activities
- Facilitate decomposition and nutrient cycling by mixing organic matter with soil
- Enhance water infiltration and drainage
- Arthropods (e.g., mites, collembola, insects):
- Break down organic matter, aiding in decomposition
- Regulate populations of other soil organisms through predation
- Contribute to soil structure formation and nutrient cycling
- Algae:
- Photosynthesize and contribute to soil organic matter
- Fix atmospheric nitrogen in some cases (e.g., cyanobacteria)
- Help in soil stabilization and moisture retention
- Archaea:
- Involved in nutrient transformations, particularly in extreme environments
- Some species contribute to nitrification and methane production