The agricultural revolution of 10,000 years ago was thought to be a unique hallmark of Homo sapiens. Now, we know that termites cultivate monocultures of fungi and damselfish farm algae. Humans and animals aren’t the only ones farming – microbes are doing it, too, according to researchers who discovered that a fungus can farm bacteria.
The soil fungus Morchella crassipes, also known as thick-footed morel, is a decomposer as well as a beneficial mycorrhizal fungus that forms symbiotic relationships with plants. The thick-footed morel is also a bacterial farmer. Here are five characteristics of human agriculture that the thick-footed morel also uses to farm the bacteria Pseudomonas putida.
In human agriculture, improving a crop’s growth conditions is cultivation. Researchers saw that the thick-footed morel was producing compounds that helped P. putida grow. In fact, P. putida grew significantly more with the help of the thick-footed morel than without it.
Researchers found that the fungus was harvesting bacteria when conditions favored resource storage. The fungus are also likely eavesdropping on signals between bacteria to detect how dense the bacteria are growing before harvesting them. To prove the fungus was receiving a benefit from the bacteria, the scientists labeled carbon molecules in glucose and observed the labeled molecules moving from bacteria to fungus. This study is the first to demonstrate carbon transfer from bacteria to fungi.
The thick-footed morel develops structures called sclerotia, which aid in survival by allowing the fungus to store harvested carbon from the bacteria. The fungus can access these nutrient stores when external resources are scarce, much like a grain silo for humans. The researchers washed the storage structures repeatedly and discovered that hundreds of thousands of bacteria are attached to each of the structures. In fact, scientists observed that the thick-footed morel benefited with a reduced stress response.