Scientists sequence genome of tomato bacteria related to human infection

Thursday, August 21st 2003, 12:00 am

By: News On 6

WASHINGTON (AP) _ A discovery about how a bacteria infects tomatoes and speckles them with black spots could shed new light on an infection that causes rashes, and sometimes death, in humans.

Knowing which proteins cause infection will help scientists find a way to stop the bacteria _ tomato speck _ from injecting itself into cells, said Greg Martin, a scientist at the Boyce Thompson Institute for Plant Research.

``Just understanding fundamental processes about how the bacteria infects hosts will give us new targets to be able to go in and interfere with the infections,'' Martin said in an interview this week.

Tomato speck, or pseudomonas syringae, is cousin to a germ that causes illness in humans. The bacteria are found in soil, water, plants and animals.

Tomato speck usually doesn't wipe out crops, but it is difficult to get rid of. Farmers usually rely on copper-based sprays to kill the germ, but it is becoming resistant. Strains of it also attack other plants, such as beans and mustard.

In people, the cousin of this germ, pseudomonas aeruginosa, attacks those with weak immune systems, causing symptoms such as rashes, pimples and nausea. Patients with the lung disease cystic fibrosis can suffer heart failure if they become infected. Pseudomonas aeruginosa also can cause ear infections and the illness meningitis, which inflames tissue in the brain and spinal cord.

Doctors are faced with the same problem as farmers _ the bacteria is becoming resistant to the antibiotics they depend on to kill it.

Dennis Ohman, a microbiologist at Virginia Commonwealth University, said he and other researchers can use the sequenced genome of tomato speck to learn more about the human infection.

``They're very similar organisms,'' said Ohman, who is on a team studying the genome of pseudomonas aeruginosa. ``A lot of the same factors that were prevalent in plant disease were there in human disease as well. The human disease and plant disease may not be all that different.''

Plant scientists found there are more than 5,500 genes, or proteins, in tomato speck. Of those, as many as 50 are key in spreading infection, Martin said.

The bacteria ``has an amazing way of injecting them into the host cell,'' he said. ``It develops a little syringe-like structure, pokes a hole into the host cell, and then it starts injecting these proteins.''

The effort to sequence the tomato speck genome was led by researchers at Cornell University, The Institute for Genomic Research, Boyce Thompson Institute for Plant Research, the Agriculture Department, University of Missouri, University of Nebraska and Kansas State University.

The findings were published Wednesday in the journal Proceedings of the National Academy of Sciences.