Nav: Home

New insight into the molecular weapons of the plant microbiome

February 05, 2018

Like all organisms, plants are associated with bacterial communities in which helpful and harmful bacteria compete for dominance. Among the weaponry of these warring bacteria are molecular syringes that some bacteria can use to inject toxins into others. In a study published in the Feb. 2 issue of the Journal of Biological Chemistry, researchers at McMaster University in Canada pinpointed the identity of one such toxin used by a soil-dwelling bacterium that protects plants from disease.

The bacterium Pseudomonas protegens can kill soil-dwelling plant pathogens, including fungi and bacteria that attack the roots of important crops such as cotton. Pseudomonas protegens releases diverse antimicrobial compounds into the soil, but John Whitney was curious specifically about the compounds that it was injecting directly into other bacteria through the type VI secretion system, or T6SS.

"[The T6SS] is this molecular nanomachine that injects toxic protein into other species of bacteria and kills them," Whitney said. "Plant protective bacteria that have [T6SS] can protect plants from pathogens better relative to [bacteria] that don't have it."

Jenny Tang and Nathan Bullen, undergraduate students from the University of Waterloo working with Whitney on a co-op work-study assignment, spearheaded the discovery that the toxic protein used by P. protegens against other bacteria acts on a molecule found in nearly all living cells: nicotinamide adenine dinucleotide, or NAD+. NAD+ is a cofactor, or "helper" molecule, in many biochemical reactions. By injecting a protein that destroys NAD+, P. protegens is able to kill other bacteria.

The team then investigated the genome sequences of many other bacteria to see how widespread the strategy of targeting NAD+ is in microbial warfare. They found that many bacteria with secretion systems carry genes similar to the one encoding the NAD-targeting toxin.

"We started to see that this isn't just a way of killing that is enacted by plant-protective bacteria," Whitney said. "If you look at the distribution of this (protein) among all sequenced bacteria, it appears that many different bacteria in many different environmental niches use this mode of action to outcompete other bacteria."

The abundance of these toxins in nature raises many questions: How do different bacteria in different environments evolve to resist this toxin? Are NAD-targeting toxins more effective against some bacterial species than others? Understanding the diversity of bacterial weapons is an active area of study among agricultural researchers who would like to develop better ways to fight plant diseases.

"The identification and characterization of antibacterial toxins produced by plant-protective bacteria may one day allow us to engineer these bacteria to have enhanced ability to suppress pathogens," Whitney said.
-end-
The work was funded by McMaster University and the Natural Sciences and Engineering Research Council of Canada.

About the Journal of Biological Chemistry

JBC is a weekly peer-reviewed scientific journal that publishes research "motivated by biology, enabled by chemistry" across all areas of biochemistry and molecular biology. The read the latest research in JBC, visit http://www.jbc.org/.

About the American Society for Biochemistry and Molecular Biology

The ASBMB is a nonprofit scientific and educational organization with more than 12,000 members worldwide. Most members teach and conduct research at colleges and universities. Others conduct research in various government laboratories, at nonprofit research institutions and in industry. The Society's student members attend undergraduate or graduate institutions. For more information about ASBMB, visit http://www.asbmb.org.

American Society for Biochemistry and Molecular Biology

Related Bacteria Articles:

Conducting shell for bacteria
Under anaerobic conditions, certain bacteria can produce electricity. This behavior can be exploited in microbial fuel cells, with a special focus on wastewater treatment schemes.
Controlling bacteria's necessary evil
Until now, scientists have only had a murky understanding of how these relationships arise.
Bacteria take a deadly risk to survive
Bacteria need mutations -- changes in their DNA code -- to survive under difficult circumstances.
How bacteria hunt other bacteria
A bacterial species that hunts other bacteria has attracted interest as a potential antibiotic, but exactly how this predator tracks down its prey has not been clear.
Chlamydia: How bacteria take over control
To survive in human cells, chlamydiae have a lot of tricks in store.
Stress may protect -- at least in bacteria
Antibiotics harm bacteria and stress them. Trimethoprim, an antibiotic, inhibits the growth of the bacterium Escherichia coli and induces a stress response.
'Pulling' bacteria out of blood
Magnets instead of antibiotics could provide a possible new treatment method for blood infection.
New findings detail how beneficial bacteria in the nose suppress pathogenic bacteria
Staphylococcus aureus is a common colonizer of the human body.
Understanding your bacteria
New insight into bacterial cell division could lead to advancements in the fight against harmful bacteria.
Bacteria are individualists
Cells respond differently to lack of nutrients.

Related Bacteria Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#514 Arctic Energy (Rebroadcast)
This week we're looking at how alternative energy works in the arctic. We speak to Louie Azzolini and Linda Todd from the Arctic Energy Alliance, a non-profit helping communities reduce their energy usage and transition to more affordable and sustainable forms of energy. And the lessons they're learning along the way can help those of us further south.