Dead bacteria can detect their presence in the soil of living beings. New research led by Michigan State University integrative biologists shows that it can have significant consequences for antibiotic resistance in farmers.
The results were published on March 24 in the journal Used and Environmental Microbiology.
The World Health Organization has called antibiotic resistance one of the biggest threats to food security. Bacterial infections that can withstand antibiotics are a major concern for the welfare of animals, the food industry and the public.
“Outside of antibiotic therapy it’s not talked about as quickly as it should,” said Sarah Evans, a professor at the School of Natural Science and Ecology, Evolution and Behavior Program. “We thought these were activities that needed to be learned more in school.”
So Evans and his team took a closer look at one of those processes: how DNA from deadly pathogens can introduce antibiotic resistance to living bacteria in soil. With a good understanding of that process, the company seeks to find ways to help break it.
“People think a lot about living bacteria,” said Heather Kittredge, who led the research for Evans ’lab as a medical student. “Perhaps we should think of the dead. They have a living function rather than death.”
The idea may sound like it is from a zombie movie. It is, however, an established and fixed – yet unknown – part of evolution. This is an example of what is called horizontal gene transfer, where genes are passed on before they are passed on.
When the bacteria die, they break down and leave DNA. This allows the living bacteria to collect those genes and use them in the process. For example, if a dead bacterial seed contains genes that help protect against an antibiotic, a living microbe can pick it up and gain their control.
Microbiologists have studied the genetics and bacteria in petri dishes to see how antibiotic resistance spreads. But little is known about the nature of the process in terms of, especially in the soil, where antibiotic -resistant pathogens grow and end up damaging human health.
“The soil is kind of a black box,” said Kittredge, a postdoctoral researcher at the University of Connecticut. “We want to know how this works in the forest, what factors affect it and what we can do about it.”
To learn all of this, the Spartans collected soil samples from around WK Kellogg Biological Station, of which Evans was a principal. They cleaned the soil and combined the living cells of the soil bacterium Pseudomonas stutzeri with DNA from the antibiotic species of P. stutzeri. They can observe when DNA has been implanted under different conditions.
What they found was that living bacteria were able to attach to DNA while at low concentrations and living cells could collect DNA that was maintained within 15 days of the experiments. But DNA seems to live in the soil sooner than that, Kittredge added.
“On the whole, this work shows dead bacteria … an unnoticed pathway of antibiotic resistance,” the company wrote in its press release.
The researchers also found that more living cells attach DNA from dead cells when they first came in contact with it, which is not surprising. Living cells need to touch DNA in order to collect it.
Surprisingly, it is responsible for soil moisture. Although living cells collect DNA in the form of natural water levels, it is more efficient in slightly dry conditions. But the more resistant the bacteria are to the wet soil, the more likely they are to break down DNA.
“They’re growing at high water levels,” Kittredge said. “So when they grow a lot it’s not like when they have the highest number of gene transfer.”
So why aren’t bacteria that are more complex and more efficient at collecting genes? That’s something the company wants to investigate, in part to understand that it can provide opportunities to prolong climate change. To date, however, this research has previously provided insights into how to modify antibiotic -resistant genes in farmers.
For example, manure from animals is used as fertilizer on farmland that is used to grow food. To help fight antibiotics, manure is often prepared to kill bacteria.
“But it’s different at which temperature the bacteria die and where the DNA is destroyed,” Kittredge said. “Increasing heat treatment to degrade DNA can go a long way.”
This work could receive applications to help researchers promote the mutation of necessary genes.
Bacterial infections: Stable allies resistant to antibiotic resistance
Heather A. Kittredge et al, Death but Not Forgotten: How Extracellular DNA, Moisture, and Space Modify the Horizontal Transfer of Extracellular Antibiotic Resistance Genes in Soil, Used and Environmental Microbiology (2022). DOI: 10.1128 / aem.02280-21
Presented by Michigan State University
Directions: On the ground, death will not end with the spread of antibiotic resistance (2022, April 11) Retrieved 11 April 2022 from https://phys.org/news/2022-04-soil- death-doesnt-antibiotic-resistance.html
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