Benefits of Aerobic Fungi

By Elaine Ingham, PhD

No one organism, no one species or no one group does it all. There are many things that the right set of organisms will provide. The following interactions and functions are the basic, underlying principles of why sustainable agriculture works.

Build soil structure and aggregate the clay colloids to open up passageways, but aggregate sand to slow water movement. The consequences of doing this are staggering, although people don’t really think about all the potential problems that will be ameliorated if compaction is ended in their soil. To stop soil compaction from occurring, the right sets of organisms need to be present and not destroyed. Structure is only built by the organisms. Growing, living sets of organisms are needed to constantly repair any damage.

It’s important to prevent erosion and loss of nutrients from the soil. Leaching losses as well as gaseous losses must be prevented.

Cycle into plant-available forms. Aerobic organism interactions convert plant unavailable nutrients into plant available nutrients, mostly around plant roots, and mostly when plants are growing and need nutrients. Aerobic organisms also compete with, inhibit and consume disease-causing organisms (pathogens) as well as pests.

Bacteria eat simple foods like sugar: very easy-to-use straight chains of carbon. They can’t use anything tough or difficult to break up, nor complex side chains because their enzymes can only attack the outside layer of foods. If the food is complex—highly folded and wrapped around itself—bacteria will be limited in growth because they can only work on the outside layer.

Leaf surface magnification
Leaf surface magnification, www.uq.edu.au

A Hunger For Carbon

Fungi eat the more complex foods, because they make enzymes that can attack the outside layer and inside layers of complex, folded, gnarly, nasty, wide C:N ratio materials.

As the bacteria eat, they have to find all the other nutrients that aren’t in the food resource to be able to use that food. That means for every five carbon (C) they consume, one nitrogen (N) has to be eaten as well. For every 50 C, one phosphorous (P) must be brought into the body, typically as phosphate (PO4). Calcium, manganese, copper, zinc, boron, iron, and all the normal components of living tissue have to be in close vicinity for a bacterium so they can grow and produce new individuals of bacteria. All life requires the proper balance of nutrients in order to increase in size, or in numbers.

But bacteria are small. If the balance of nutrients isn’t right in the few micrometers around the bacterium, it will stop growing. So bacteria need to be in places where there is movement of nutrients going by for the bacterium to grab, or in a place where there are many available nutrients.

With this need for constant supply of the right balance, it is easy to see that any individual bacterium isn’t often going to be active and growing because the specific set of conditions where it’s happy will rarely be met. Thus, we need to have thousands of species of bacteria in each tiny bit of soil to be able to have some set of bacteria awake and functioning regardless of the conditions. There has to be a constant influx of bacterial foods as well.

Fast-Food Feeding Frenzey

Because of their growth requirements, bacteria are excellent at waking up rapidly, growing for short times, then going back to sleep rapidly. They wake up, grab the nutrient passing by and go back to sleep. Bacteria can’t be beat in terms of their ability to grab—but only when they are awake. If there is a large pool of leachable nutrients in the soil, wake the bacteria up, or send in new bacteria, to grab them, sequester them, and hold those nutrients in the soil. This is the practical way to prevent leaching of nutrients.

Another consideration is that because most of the food that bacteria consume contains much more carbon (C) than any other nutrient, bacteria need to get rid of the "excess C" and grab absolutely every bit of N it can possibly find. That means bacteria, in general, release a great deal of the carbon in the plant material they are consuming as carbon dioxide.

As a result, having only bacteria active in the soil means that a great deal of the carbon in organic matter will be "blown off" as carbon dioxide.

Thus, bacteria are great holders of any nutrient, except carbon. If the soil is disturbed a great deal, and the nutrients in the soil are mixed with high carbon plant litter material, then most of the soil carbon will be lost as bacteria blow off the carbon as CO2.

Fungi, on the other hand, don’t do this—and I mean beneficial fungi not disease causing fungi, which are a whole different group of outlaws and certainly should be regarded as one set of "bad guys" in the plant world—have much wider C:N ratios in their bodies.

Thus fungi grow on foods that bacteria can’t grow on.

Fungi grow as long threads, and so they can reach anyplace in the soil and bring back nutrients from anyplace they can reach to support their growth. Not just mycorrhizal fungi, which get their sugar (carbon) from the plant, but all beneficial fungi send out threads to access all the different nutrients needed to grow, even when growing on the nastiest, lowest N, P, K, etc., foods you want to talk about.

Laying the Carbon Pipeline

Because fungi grow as long pipes that turn increasingly into carbon pipes as the fungal strands (hyphae) get older and older, a major function of fungi are to make carbon storage forms and increase the soil organic matter content.

If you want to build the carbon content of soil and build some really long-term storage forms in soil, fungal growth and biomass is required.

Could we solve the elevation of carbon in the atmosphere in a short time? Absolutely. This happens when people stop growing bacteria and start growing fungi in their soils. Or even if they would stop destroying fungal biomass in soil, no further elevation in global carbon in the atmosphere would occur.

Where Is All The Carbon?

In 2001, the Soil Science Society of America drafted a position paper that included this statement: "Worldwide, the top 1 meter of soil comprises about 3/4 of the earth’s terrestrial carbon; nevertheless, there is tremendous potential to sequester additional clearing and tillage. Such conventional farming practices ‘burn’ soils organic carbon just as we burn fossil fuels today. However, in the case of soil's organic carbon this historical decline can be reversed, which is not the case for fossil fuel reserves." www.soils.org/Exit Site (.pdf)

Carbon Structure of Simple Foods

Think of enzymes as being like teeth. If you only have incisors to grab things, you can’t really chew your food. The food has to be simple fluids. But if you have molars, cutting teeth and incisors, then you are equipped to grab hold, cut, and grind, which makes more foods available to you.

In the examples below, the symbol means a bond where the material at either end of the bar have combined, sort of like two people hugging each other. Carbon, or C, is a special material because it can "hug" four different things at the same time. To reduce the amount of business in the following examples, remember that each C has two hydrogens (H) associated with it in most cases, so that the C is hugging four things, two of which are usually H. (There are no or few branches in the carbon chain, few kinds of links and the structure is very linear, which means only a couple of enzymes are needed to chew this food up.)

Simple and linear (with no branches) sugars or proteins

CH2-CH2-CH2-CH2-CH2-CH2-OH
(Leaving out the H from now on)

C – C – C – C –NH2
A bit more complex (with branches)

C –C – C –C – C –C
C
C

These are bacterial foods, and almost strictly bacterial foods. Only a very few species of fungi could even begin to compete with bacteria for these foods, if bacteria are present.

Some folks have made the mistake of saying that fungi use simple foods when the testing did not include any of the normal sets of bacteria. If these bacteria are present, fungi will always lose, because bacterial enzymes are faster at grabbing these simple foods, use less energy to break these simples [sic] linkages down into component parts for the bacteria to consume and turn into new bacterial biomass.

Increasingly More Complex

Link 100 of the more complex carbon chains together in a long chain, end to end, with a few linking through the branched side chain.

Link 100 of the more complex chains together, but link them in ANY position, not just end to end.

Link 1000 of those groups of 100 together [sic], and let any free end loop around and link to any other C that can drop an H and hug another carbon.




Elaine Ingham

Author Dr. Elaine Ingham, soil researcher, ‚ÄéChief Scientist at Rodale Institute in Pennsylvania.

Say hello and connect with Elaine at LinkedIn | YouTube | Website




Related:

Spinach leaves

Soil Health Topics
Composting tips and working with "good guy" fungi.