The Soilsmith – Bruce Davison – #RegrariansTALK 10


Fats may limit cell organism size in carbon-rich media


Bacterial cells in carbon-rich media (purple and blue) grow twice as big as those in carbon-poor media (green). New research shows they can grow big, however, only if they can make fats with the carbon.

Fat (lipids) limits how big bacterial cells can be. “If you prevent cells from making fat, they’re smaller, and if you give them extra fat or allow them to make more fat, they get bigger,” said Levin, professor of biology in Arts & Sciences. “Fat makes cells fat.”

“If we hit the cells with an antibiotic that targets fatty-acid synthesis, we really saw a significant drop in cell size” Vadia said.

Also, by turning up FadR, a transcription factor that activates expression of the fatty-acid synthesis genes, the cells got bigger.

“It doesn’t seem to matter what the lipids are, really,” Levin said, “provided you have enough of them. We found we could give the cells oleic acid, a fat found in avocados and olive oil, to supplement diminished fatty-acid synthesis and as long as the added fatty acid got into the membrane, the cells could recover.”

A little place for my stuff | EurekAlert! Science News

Fatty Acid Availability Sets Cell Envelope Capacity and Dictates Microbial Cell Size: Current Biology

Hydrogenation: transform liquid oil into solid fat
Applied Science

Olive Oil Did WHAT to my Triglycerides??!!?? (Pt 2)

Mulch, mulch, mulch, mulch, mulch; that’s the sound of happy soil biology.

The Natural Farmer

Great episode from Jagannath.

Comments: straw tends to be high in lignin which needs white rot fungi to break it down, which requires moisture and gives rotted wood it’s soft spongy characteristic. Straw is probably better as a winter rather than summer mulch which is why I have a rule of thumb to use soft mulch in summer and hard mulch in winter. Grow your mulch in spring for summer! Prune for winter!
Interestingly leaf litter can also almost contain as much lignin as straw. Sugar cane mulch on the other hand has about 1/3 the lignin of straw and corn stalks are half that again, sugar cane mulch has an ideal carbon to nitrogen ratio of 50:1 though. Corn can actually be quite good for building soil carbon so long as the mulch is left in place and a green added to it, like Jagannath’s planned legume companion.
Also, the allelopathic leaves mentioned can be used after a quick 3-day hot compost. Putting them in a black bag in the sun with some urine may work too.
I find legumes like beans are a great indicator of soil bulk density. They tend to thrive in loose soil where air gets the root zone. The other thing Jagannath may be missing for his soil and environment with such dry lifeless soil is the rhizobia inoculant that form the nitrogen-fixing symbiosis in the form of root nodules. Here in Australia there’s a trial going on to match the microbe with the legume so that farmers can inoculate at sowing time, apparently we don’t get the same level of root nodulation and yield compared to other countries because of our microbial species, so efforts are being made to breed and select for them.
Today I also learned that leaf litter suppresses herbivorous nematodes likely by increasing the fungi population that trap them, while on the other hand just leaving roots in the soil increases nematodes and bacteria over time.
Lastly, I like to measure my mulch depth in buried finger knuckle joints. One knuckle joint is good, two is better, three is best! And so is using three different mulches: green, brown and white. Green for bacteria (nitrifying), brown for brown rot fungi (cellulose), and white for white rot fungi (lignin).
As you can probably tell, I consider mulch the most underrated of topics! 😛

Got Herbivorous Nematodes? Just add Leaf Litter.

leaf vs root.jpg

This study says that leaf litter was preferred by fungi and root litter by other microbes like bacteria and nematodes, and that herbivorous nematodes were controlled more by leaf litter than root litter.

Probably by the fungi catching the nematodes with lasso! Yeehaw.

It also suggests that cutting plants at the stems and just leaving the roots to feed soil microorganisms may increase nematodes over time, especially when nitrogen or phosphorus is added. Phosphorus is known to negatively impact on fungi populations, while nitrogen amendment can result in plants exuding less carbon from their roots that fungi and other soil microbes feed on, microbes that then fix nitrogen and make other nutrients bioavailable for the plant.

So, if you’re doing a no dig approach to gardening and leaving roots in place, mulch is a must. Whether that’s a carbon source in the form of leaves or a low phosphorus compost mulch or otherwise, basically think of the fungi!

Fungi wake & feed bacteria in dry and nutrient poor habitats.

59 Degrees

Researchers closely examined the transport of water, substrates and nutrients through the microscopically small hyphae of fungi. They grew the fungi on a culture medium of water, glucose and nitrogen-containing nutrients. The fungal hyphae had to pass through a dry, nutrient-free zone in order to grow through into a new area containing the culture medium. The inhospitable transition zone contained spores of the common soil bacterium Bacillus subtilis. Spores are inactive stages of Bacillus that form when there is insufficient water, food and nutrients available for bacterial growth. The bacteria go into a kind of dormant stage, from which they only awake once the environmental conditions are more favourable for living again. As the fungal hyphae grew through the dry zone, the bacterial spores germinated and they noticed clear microbial activity.

The researchers then ‘labelled’ the water, glucose and nitrogen-containing nutrients in the culture medium in advance with stable isotopes. If these substances were transferred from the fungus to the bacteria, they could be detected using the isotopic marker.

They found stable isotopes of the labelled water, glucose and nitrogen-containing nutrients in the cell mass of the bacteria — which could only have come from the fungi.

Fungi awake bacteria from their slumber