All Hydro 101

The pH connection between bacteria and fungi

So, first things first. I’m sure you are wondering, “What kind of person blogs about soil, pH bacteria and fungi?” Good question!

I, your host, Derex Zellars am an Environmental scientist by training with a big interest in Environmental Microbiology and other microscopic organisms. I’ve worked on a few soil bioremediation systems, phytoremediation restoration projects, and bacteria isolations with applied formulations. Without question, it has been an interesting journey working with and examining these systems for differences and similarities. Personally, I like to focus on the similarities. Bacteria and fungi need to perform some of the same functions as higher organisms. For example, they need to take in nutrients and let out waste. They may be single cells, but they have to communicate with other organisms around them. One globally significant example of their communication is their integral involvement in plant survival, they breakdown of organic molecules making nutrients available to plants. Just from that description alone, they are having more complex interactions than I am!

And that’s what leads me to write this blog. I would love to talk about that stuff. One of the goals for my blogging is to tell you about great research being done on fungi and bacteria found in soil, and how it relates to plant growth. The other goal is to learn. There’s an endless amount of info out there on soil biochemistry, agriculture or horticulture, and microbe biology. All we have to do is learn it. Seems easy enough, right? Well, hopefully, you’ll enjoy learning some this stuff along with me, and enjoy dissecting the plant, microbe, grower relationship.

The basic question driving this blog is, “What does soil need to have in it to allow for optimal plant growth?” The answer to this question is of course different depending on what you’re growing, how much of it you’re growing, and where you’re growing it. But, if I had to pick one characteristic of soil as being super important, I’d go with pH. Why? Because pH impacts composition of microbes and nutrient availability in soil.

Nitrogen, phosphorous, and potassium are the major macronutrients taken in by plants from soil. Organic sources of these elements are dependent on the activity of bacteria and fungi to release them in the soil. From this, you can reason soil pH affects bacteria and fungi, and bacteria and fungi affect nutrient availability, therefore soil pH affects nutrient availability. In addition to messing up nutrient availability from organic sources, bad soil pH can lead to leaching of inorganic nutrient sources, and can even contribute the buildup of toxins like aluminum. All of this just highlights the importance of soil pH.

pH is a scale to indicate the acidity or basicity of a solution or substance. Anything at the far ends of the pH scale in either direction, acidic or basic is highly reactive. For example, relatively neutral soil, pH 6.5, won’t react with aluminum, but acidic soil will react with aluminum, allowing it to be taken up by plants. This is toxic. Because pH is so important to plant survival, I think we should take time to examine the specific affect soil pH has on bacteria and fungi. At pH 2, which is about as acidic as our stomach acids, both bacteria and fungi don’t do so well. However, as pH increases lots of bacteria can growth and proliferate. A British group found over four times as much bacterial biomass in soil samples at pH 8.3 compared to pH 4.5. pH 8.3 is approximately 10,000 times less acidic than pH 4.5. We still have to be careful not to let our soil become too basic, as very high pH values can be just as toxic to plants.

Now that we know there can be big changes in bacterial biomass in soil depending on pH, we can ask, “What’s happening with fungi?” In short, nothing. The same group that found over a four-fold change in bacteria, found no significant changes in fungal biomass along this same pH gradient when they didn’t deliberately inhibit bacterial growth. The relative stability of the fungal biomass could mean that at lower pH values, fungal activity becomes more important to maintaining nutrient availability. It’s a good thing then that fungi seem to have a wider pH range for optimal growth.

Knowing a little bit about soil pH is definitely a good place to start my next blog post.

Click here to read The Soil Blog part 2

Rousk J, et al Soil bacterial and fungal communities across a pH gradient in arable soil. The ISME Journal (2010) 4, 1340-1351.
Derex Zellars, B.S. Environmental Science