Green Plants Share Bacterial Toxin

November 6, 2006
Green Plants Share Bacterial Toxin
Green fluorescence shows lipid A, previously known only as a toxin from bacteria, in leaves from pea seedlings. ((Peter Armstrong/UC Davis photo)

A toxin that can make bacterial infections turn deadly is also found in higher plants, researchers at UC Davis, the Marine Biology Laboratory at Woods Hole, Mass. and the University of Nebraska have found. Lipid A, the core of endotoxin, is located in the chloroplasts, structures that carry out photosynthesis within plant cells.

The lipid A in plant cells is evidently not toxic. The human intestine contains billions of Gram-negative bacteria, but lipid A does not become a problem unless bacteria invade the bloodstream.

"We've no idea what it's doing, but it must be something important because it's been retained for a billion years of evolution of plant chloroplasts," said Peter Armstrong, professor of molecular and cellular biology at UC Davis and senior author on the paper.

Endotoxin is better known to bacteriologists and physicians as part of the outer coat of Gram-negative bacteria such as E. coli. The lipid A core of bacterial endotoxin activates the immune system and can cause septic shock, a major cause of death from infection. It is distinct from the toxin found in E. coli strain 0157, responsible for the recent outbreak of food poisoning tied to spinach.

Bacteria were thought to be the only source of lipid A. However, R.L. Pardy, professor at the University of Nebraska-Lincoln, recently found a similar molecule in Chlorella, a single-celled relative of more advanced plants. Armstrong's lab at UC Davis developed methods to visualize lipid A in cells, using a protein from the immune system of the horseshoe crab, and the researchers began collaborating.

"It was one of those celebratory moments, when I looked in the microscope and saw these gloriously stained algal cells," Armstrong said, describing their first experiment. The group has now found lipid A in chloroplasts of garden pea plants as well as green algae, and Armstrong suspects that it is present in all higher plants with chloroplasts.

That idea is supported by genetics. Sequencing of the Arabidopsis genome -- the first higher plant to have its entire DNA sequence read -- revealed that the common lab plant has all the biochemical machinery to make lipid A, an observation that had gone largely unnoticed until now. Chloroplasts themselves are thought to have evolved from cyanobacteria, independent photosynthetic bacteria that took up residence in ancestral plant cells.

Source: UC Davis

Explore further: First study of radiation exposure in human gut Organ Chip device offers hope for better radioprotective drugs

Related Stories

New method to stop cells dividing could help fight cancer

January 18, 2018

Researchers at Uppsala University, Karolinska Institutet, and the University of Oxford, have used a new strategy to shut down specific enzymes to stop cells from dividing. The method, published in Cell Chemical Biology, can ...

A new regulator of vesicle trafficking in plants

December 28, 2017

A protein that transports the simple chemical choline plays a major role in vesicle trafficking, ion homeostasis, and growth and development in plants, according to two new studies publishing 28 December in the open-access ...

Camelina oil improves blood lipid profile

January 8, 2018

The use of camelina oil reduces overall and LDL cholesterol levels in persons with impaired glucose metabolism, according to a new study from the University of Eastern Finland. The findings were published in Molecular Nutrition ...

Recommended for you

Unprecedented study of Picasso's bronzes uncovers new details

February 17, 2018

Musee national Picasso-Paris and the Northwestern University/Art Institute of Chicago Center for Scientific Studies in the Arts (NU-ACCESS) have completed the first major material survey and study of the Musee national Picasso-Paris' ...

Scientists shed light on biological roots of individuality

February 16, 2018

Put 50 newborn worms in 50 separate containers, and they'll all start looking for food at roughly the same time. Like members of other species, microscopic C. elegans roundworms tend to act like other individuals their own ...

Researchers create first superatomic 2-D semiconductor

February 16, 2018

Atoms are the basic building blocks of all matter—at least, that is the conventional picture. In a new study, researchers have fabricated the first superatomic 2-D semiconductor, a material whose basic units aren't atoms ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.