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)

Should you use plastic weed mat?

Comments and Questions 6 20 2017

Kevin answers questions and comments on his videos about a range of topics and emphasises the importance of soil, water and air.
Here I want to emphasise the importance of plants and organic mulch too.
One of the comments on his Q&A video was the following after seeing Kevin’s use of weed mat “to keep the soil covered”:

My only experience with weed mat, was pulling one up, and finding stinky dead earth beneath

Now it sounds like this person’s plastic weed mat caused the soil below it to turn anaerobic due to either a lack of air penetrating the mat or retaining too much moisture which then excluded the air from entering the soil. When this happens the soil begins to anaerobically digest and produce alcohols, phenols, and gasses such as methane, the scent of sewer gas.

Not ideal plant growing conditions!

However there can be benefits when using plastic weed mat in the right conditions that does let air and water through, as the mat can help keep the soil moist, especially in drier regions. Weed mats can also warm or cool the soil depending on how much sunlight they absorb or reflect. They can also help prevent erosion. But the main reason people use it, is because the mats also reduce weed competition for plants planted into or near the weed mat. Reduced competition for water, sunlight, and for nutrients.

However the biggest problem with plastic weed mat when growing and assuming the correct mat was chosen for the conditions, is that if left on for extended periods, the soil often tends to breed plant pathogens. This happens when soils are not amended with a high carbon source such as plant leaf litter, plant exudates, or an organic mulch.

In soils that are kept moist and aerated and warm the microbiology and fauna become more active and will chomp through organic matter like there is no tomorrow. In doing so there is an increase in soil carbon respiration in the form of carbon dioxide and methane along with other gasses. This increase in respiration can actually help increase plant growth by providing carbon dioxide concentrated around the plant leaves. The increase in microbiological activity also increases nutrient cycling and plant available soil nutrients. However if the plants aren’t putting the carbon back into the soil via their roots, exudates, or plant litter when they die – then over the long term the soil community suffers.

When there is a lack of high carbon input that organic mulch provides to soil organisms, competition for that soil carbon increases. And the less soil carbon, the less complex organisms will survive. This is particularly important for fungi that rely on the carbon because they are made up of more carbon than other microbiology. Worse, the fungi that do survive the hostile conditions are often those that are plant predators able to fight for the carbon needed in order to survive because they now lack competition. As a result those predators infect plants and reduce yields or even kill them, and so gardeners and farmers search for solutions to their fungal problems in the form of fungicides. As a result fungi get a bad name. The same happens to nematodes.

However for short season plants like seasonal crops in Kevin’s example, this may not be much of a problem as the plant may be ready for harvest before the predators have overcome a plants defences, and he’s adding organic matter every year.

To conclude, when organic resources are plentiful, everyone’s happy and works in symbiosis, and when they’re not happy it’s war. Not quite extremophile Star Wars, but certainly localised Planet Wars, and eventually those wars include us higher order carbon beings in Human Wars that result from desertification and a lack of resources.

Plastic mulch is also plastic. Did you know that most sea salt already has microplastics in it after a little over 100 years of plastics use?

Breaking the Oxygen Barrier in Microbial Cultivation

Oxygen comprises one fifth of our atmosphere, and we take for granted that this a good thing. After all, aerobic creatures like ourselves could not exist without free O2. Not all life shares this feeling. Oxygen and its derivatives (known as “reactive oxygen species” or ROS) can wreak havoc on the biochemistry of many microbes. For some obligate anaerobes such as methane-producing archaea, even a small trace of oxygen poisons them irreversibly (see, for example Kiener and Leisinger 1983). Others fall somewhere in the middle. Microaerophiles (e.g. Helicobacter pylori, the cause of gastric ulcers) require small amounts of oxygen but are unable to tolerate full atmospheric concentrations (Bury-Moné et al., 2006).

Why are these organisms sensitive to oxygen?

Find out why at:
Small Things Considered: Breaking the Oxygen Barrier in Microbial Cultivation

Biochar, The Soil Capacitor

Work With Nature

David talks about his biochar experiments and that got me thinking…

Recently I watched a great talk about the negative priming effects of pyrogenic carbon on soil organic carbon that you may find interesting:

Extrapolating from Silene’s results, when biochar concentration is high enough (~3%) there should be a halving of soil organic carbon (SOC) priming, and this should cause a doubling of SOC sequestration and effectively grow high carbon content Terra Preta soils faster. This correlates well with other research I’ve seen by David Johnson.

What the biochar is doing is interesting. I’ve hypothesised that microbes change metabolic strategy in the presence of enough carbon and in particular high electron transfer biochar, as recently biochar has been shown to increase electron transfer within soils.

So in addition to nutrient sorption, biochar may be acting as a sort of microbe electricity grid, and moving their metabolism from one of oxidation to reduction as they get their energy from the grid, thereby facilitating more SOC sequestration.

If this is the case, to facilitate this we may want high electron transfer biochars that have large surface areas that are effectively many aggregate soil capacitors, which made me think of Robert Murray-Smith’s recent videos in which he creates his own graphene inks for batteries and capacitors, and has been recently been talking about his strange capacitors.

I know from other research that the most productive soils long-term are those that are most connected ecologically, not fungal dominated, though that helps up to a point, and creating these connected soils is important if we want productive systems. This electron transfer effect that biochar has may be one small part of the puzzle along with plant roots, mycorrhizal fungi and other interconnected ecosystems we’ve yet to discover.

Also, if I calculated correctly, in Silene’s video, 450C carbon-13 tagged biochar soil appears to respire at a rate about 13x slower than SOC, so it’s not going to stay around forever.

Plant Growth Promoting Rhizobacteria Biofertilisers.

Earth Man Living Soil

Plant growth promoting rhizobacteria are the soil bacteria inhabiting around/on the root surface and are directly or indirectly involved in promoting plant growth and development via production and secretion of various regulatory chemicals in the vicinity of rhizosphere. Generally, plant growth promoting rhizobacteria facilitate the plant growth directly by either assisting in resource acquisition (nitrogen, phosphorus and essential minerals) or modulating plant hormone levels, or indirectly by decreasing the inhibitory effects of various pathogens on plant growth and development in the forms of biocontrol agents. Various studies have documented the increased health and productivity of different plant species by the application of plant growth promoting rhizobacteria under both normal and stressed conditions. The plant-beneficial rhizobacteria may decrease the global dependence on hazardous agricultural chemicals which destabilize the agro-ecosystems.

Mechanisms and applications of plant growth promoting rhizobacteria: Current perspective


Cover Crops May Increase Soil Microbial Biomass 3x More Than Compost

Three to six times more microbial biomass carbon and nitrogen depending on soil type.

These results provide evidence that carbon (C) inputs from frequent cover cropping are the primary driver of changes in the soil food web and soil health in high-input, tillage-intensive organic vegetable production systems.

Fresh is best.

Cover cropping frequency is the main driver of soil microbial changes during six years of organic vegetable production

Microbial communities affected by type of carbon “food” sources


A new study has found that:

The type of carbon source affects not only the composition and activity of natural microbial communities, but also in turn the types of mineral products that form in their environment.

“We’ve illustrated that as microorganisms alter their environment, their environment then affects the type of microorganisms that are there and their activity.”

Researchers took anaerobic respiration microbial communities and presented them with one of three carbon sources: glucose, a six-carbon sugar; lactate, a four-carbon compound; or acetate, a simple two-carbon compound.

Their analysis showed that a distinct series of changes occurred consistently when microbes were exposed to lactate or acetate-rich environments. However, in glucose-rich environments, they observed varying patterns of changes.

“We think that, because glucose is a larger, more complex compound that can be broken down into many simpler compounds, this opens up more chemical pathways in the community through which it can be used, and that this diverse metabolic potential accounts for the different patterns we’re seeing,” said O’Loughlin.

Impact of Organic Carbon Electron Donors on Microbial Community Development under Iron- and Sulfate-Reducing Conditions