Under Pressure

Recently for my main job, we were doing a light renovation of a house in Maryland where we had discovered a leak in the first-floor ceiling a couple months prior. Initially, I was under the impression that the leak was coming from the roof, as it had been re-tiled about a month prior. However, a coworker confirmed that there was no damage in the second-floor bathroom right above it - bathroom... yep, that was the source of the problem, even though we have yet to identify the exact issue.

Maybe it was the shower above the damaged area, we thought - however, this was a property left unoccupied for almost two years that had been winterized the prior year. No one would have used the shower. Then maybe the toilet drainage was the issue - maybe the contractor who worked on the roof used the toilet and it drained into the roof on the first floor? But flushing the toilet caused no issue and the rubber gasket seemed to be without problems. We honed in on it potentially being a micro tear to the toilet water-supply line although that doesn't really make so much sense given that even when the water was on, nothing seemed to be happening. Maybe only a few drops of water were leaking at a time, only causing issues when left on for an extended period of time? - how to test that - we wouldn't want to leave the water on and leave the house, as it may cause further damage.

A house being but a shallow imitation of the flesh which houses our souls, our water pipes being our arteries which carry nutrients and all manner of substances whose mechanisms I scarcely understand now and probably forever. The body being less of a high-pressure system and more of a lower-pressure one equivalent to ~2 psi but not needing high pressure given that the heart functions as a pump pushing the blood stream around. Leading me to the realization that all plants use water and pressure as the mechanism for moving fluids around, having no heart as a pump, leading me to the realization that mushrooms must be similar. A quick AI search revealing that mushrooms can exert up to ~100 psi of pressure which is how they crack through incredibly tough substances as part of their fruiting process. How does water pressure in a mushroom work?

The mechanism for mycelium breaking down oak involves turgor pressure, which acts as a directional drill. The fungus keeps the tip of the hypha soft and pliable using enzymes, then the high turgor pressure from the rest of the cell acts as a hydraulic piston, shoving the soft tip forward into the oak wood. Once the tip moves forward, the fungus calcifies the wall behind with more chitin, locking in the new growth.

The mycelium is able to project such high amount of pressure by using the following formula: osmotic pressure = iCRT

C = molar concentration of solute (glycerol)

R = gas constant

T = absolute temperature.

To hit ~100 psi, the fungus simply cranks the "C" to extreme levels. This, of course, is not achieved throughout the entire network, but only concentrated in a specialized "inflating" cell called appressorium.

How do organisms such as oyster mushrooms pump water throughout the body? It is through a mechanism called the turgor pressure gradient. In areas where mycelium is actively digesting food, it accumulates sugars and minerals. In other areas where the fungus is growing, it is consuming sugars/minerals and evaporates waters, which creators lower pressure. Then, as in all systems, the water at the higher-pressure end moves towards the lower-pressure side.

This enables the process known as cytoplasmic streaming, which is the active transport of various nutrient substances at rates of up to millimeters per hour (quite fast at a microscopic scale actually). Cytoplasmic streaming is composed of three parts: (1) Hydraulic "push" - the bulk flow, (2) molecular motors - "Actin" and Myosin" and (3) septa, which filter and regulate the movement.

So the hydraulic push and pull are enabled by turgor pressure - i.e. - differences in pressure gradients. The mycelium absorbs water at one end and lose it to growth at the tips. This creates a pressure difference whereby the water flows from higher pressure zones to lower pressure zones, allowing for phenomenon of hyphal tips being able to exert extreme pressure to allow for expansion, as explained above.

Second, the mycelium does not only rely on pressure - it also has a railroad system so to speak. Long proteins called actin filaments and microtubules run the length of the hypha. Then tiny motor proteins (called myosin, kinesin, and dynein) act like biological freight trains. They have "legs" that literally walk along the tracks. So the motors grab onto vesicles (tiny bags of enzymes), mitochondria, or even entire nuclei and haul them through the water. This matters because it allows mycelium to move things against flow of pressure, which is sometimes necessary.

Third, septa (which are walls that divide hyphal cells) play a critical flow in the flow of water around the mycelial body. Each septa wall has hole in the middle, which is large enough for water and nutrients to pass through but small enough to maintain "traffic control." If a hypha is cut for example or ripped out, the septa gates close and don't allow all of the water and nutrients to stream out. They do this by utilizing "woronin" bodies, which are dense protein crystals that act like ball-valves. They quickly plug holes in the septum when they detect a sudden drop in pressure, minimizing the loss of nutrients.

In conclusion, there are definitely parallels between water piping in houses and the way water functions in mycelial systems. Both maintain high pressure within the system, which pushes water out when lower pressure outlets are enabled. In houses, this occurs when opening various valves (kitchen sink, bathroom, etc.) which causes water to leak out of the low pressure opening. In the case of mycelium, as water is used to grow out, it creates lower pressure, allowing for a flow of water from the higher-pressure side (usually from stable to growing side). This is then facilitated by proteins functioning as a railway or airport walking escalators, which can either accelerate the flow of nutrients or even allow for reverse pathing against normal cytoplasmic flow. Finally, each hyphae are divided by septal walls, which function as emergency doors, closing when dangerously low pressure is detecting. Wow!! Nature is amazing!!