Microbes Quorum Sensing

550 Gigatonnes of Carbon Based life forms on Earth

A recent census of life on earth, measured in gigatonnes (Gt) of carbon, estimated there are 550 Gt of carbon based life forms on earth. (A gigatonne is a billion tonnes).

450 Gt of these life forms are plants(green plants, shrubs, vegetables, trees). All other living things make up the remaining 100 Gt.

Microscopic living organisms (Protsists, archaea, fungi and bacteria) make up 93% of the remaining 100Gt. These are the organisms that run our soils, our bodies, animal bodies, ruminant nutrition & run our plants. If we want our soils & ourselves to be healthy we have to learn how to look after these microscopic organisms. In addition to this we have to understand  viruses which are not seen as living things. They are fragments of DNA that are key determinants of the functioning of all microbes and larger things like animals and

Remaining 7 Gt Carbon

Insects, fish, mollusks, annelids, nematodes, animals, birds and humans make up the remaining 7% of Carbon in the 100 Gt. These things are the things we can see. In the final anlaysis, humans comprise only 0.01% of the carbon biomass of live on earth by weight not by numbers.

One teaspoon of healthy soil contains more microbes than all the humans on earth especially soils close to the roots of living plants. If you look at the rumen of a cow or sheep, one drop of rumen fluid contains 10,000 times more microbes than there are humans on the planet.

In a human body there is around 1 trillon human cells and 10 trillon bacterial cells – 10% human on a cell count. We have around 300,000 human gene cells but around 100 times more bacterial genes – so in effect we are actually 1% human.

The situation in plants is similar to that in animals and humans. The cells of the microbes that lives inside and outside plants significantly outnumber plant cells. So when we look at a plant we think we are dealing with plant genetics but in fact what we are dealing with is the microbes, in, on and around the plant. So we have to change our thinking. We have to start thinking about microbes, in, on and around everything.

Microbes are capable of performing lots of amazing things. Microbes communicate using quorum sensing. In the microbial world, the term quorum sensing refers to density dependent coordinated behavior that regulates gene expression in the microbial population and/ or in the host animal or plant.

In the human large intestine we have bacteria lactobacillus that manufacture B vitamins like B12. Yet many people are supplementing themselves with B12 vitamins as their body is not producing enough of it. For B12 producing lactobacillus there has to be a quorum (certain number, population) that choose to switch on their genes to produce vitamin B12. What can stop this quorum occurring? Antibiotics, chemicals placed on food you eat that result in you not having sufficient numbers of gut microbiology to create quorum to produce the vitamin required.

If we look at the parallels in soil we see exactly the same thing. We are meant to have lots and lots of microbes in our soils performing all kinds of things like producing vitamins for plants but if we are using all kinds of chemicals we will not have enough to reach a quorum that choose to switch on their genes.

With microbes quorum sensing means their will be enough microbes to turn on their genes or the genetic expression of their plant host or their animal host. This is where microbes are so incredibly powerful because they can turn plant, animal and human genes on and off.

Some of the plant genes microbes can turn on and off are those for requiring nutrients, being drought tolerant, being frost tolerant. That is why where we see in soils where microbes are reaching a quorum plants become more drought tolerant, frost tolerant and more nutrient dense.

Every kind of plant supports a different kind of microbio.

Quorum Sensing is density dependent coordinated behavior that occurs in bacteria, archaea, fungi and viruses. Every species produces it own unique signal and these chemical signals are called autoinducers. When the concentration of autoinducers in the environment reaches a critical level they regulate gene expression in the microbial population and/ or in plant or animal hosts. If there are only a few of a specific species of microbe they are going to keep quiet in self preservation to ensure they are not eaten.

Soil Food Web New Zealand

Can humans supply nutrients to plants? Of course, but we are not very good at delivering them at the right rate, in the right forms or the places that plants need them. We tend to add a huge amount at once, and hope the plant can sort it out.

Only when a healthy set of soil microbes and organisms are present will nutrients remain in the soil and be made available to plants at the right rates, in the places and the forms the plants need.

Understanding how the microbes effect soil health requires a detailed knowledge on what organisms exist in the soil, how many of them are active, how efficient the nutrient cycling capability is and if the balances are correct.

The Soil Food Web NZ team assess soil, compost, compost tea, leaf colonisation, vermicast and various other biological products for fungi, bacteria, protozoa, and mycorrhizal fungi.

Armed with this information you are then able to confidently decide on the right management tools plus weigh up how effective they are over ensuing years.

If you wish to learn more contact Cherryle Prew, Owner and Manager of Soil Foodweb New Zealand.