Navigation Links
Scientists crack code of critical bacterial defense mechanism

COLUMBUS, Ohio Scientists have combined chemistry and biology research techniques to explain how certain bacteria grow structures on their surfaces that allow them to simultaneously cause illness and protect themselves from the body's defenses.

The researchers are the first to reproduce a specific component of this natural process in a test tube an essential step to fully understanding how these structures grow.

With the new method described, these and other researchers now can delve even deeper into the various interactions that must occur for these structures called lipopolysaccharides to form, potentially discovering new antibiotic targets along the way.

Lipopolysaccharides are composed primarily of polysaccharides strings of sugars that are attached to bacterial cell surfaces. They help bacteria hide from the immune system and also serve as identifiers of a given type of bacteria, making them attractive targets for drugs. But before a drug can be designed to inhibit their growth, scientists must first understand how polysaccharides are developed in the first place.

"We were able to answer some of the questions about how components of this growth system do their jobs. This will allow us to more fully characterize lipopolysaccharide biosynthesis in vitro, a process which may shed light on useful targets for developing antibiotic agents," said Robert Woodward, a graduate student in chemistry at Ohio State University and lead author of the study.

The study is published in the April 25 online edition of the journal Nature Chemical Biology.

The researchers used a harmless strain of Escherichia coli as a model for this work, which would apply to other E. coli strains and similar Gram-negative bacteria, a reference to how their cell walls are structured.

The surface of these bacteria house the lipopolysaccharide, which is a three-part molecular structure embedded into the cell membrane. Two sections of this structure are well understood, but the third, called the O-polysaccharide, has to date been impossible to reproduce.

Two significant challenges have hindered research efforts in this area: The five sugars strung together to compose this section of the molecule are difficult to chemically prepare in the lab, and one of the key enzymes that initiates the structure's growth process doesn't easily function in a water-based solution in a test tube.

Ohio State synthetic chemists and biochemists put their heads together to solve these two problems, Woodward said.

To produce the five-sugar chain, the researchers started with a chemically prepared building block containing a single sugar and introduced enzymes that generated a five-sugar unit from that single carbohydrate.

"The first part was done chemically, and in the second part, we used the exact same enzymes that are normally present in a bacterial cell to transform the single sugar into a five-sugar string," Woodward said.

Once these sugars join to make a five-sugar chain, a specific number of these chains are joined together to fully form the O-polysaccharide. A protein is required to connect those chains the protein that doesn't respond well to the test-tube environment.

Early attempts to produce this protein in the lab resulted in clumping structures that did not function. So Woodward and colleagues produced this protein in the presence of what are known as "chaperone" proteins.

"And basically what the chaperones do is help the protein fold into its correct state. We were able to produce the desired enzyme and also were able to verify that it was functional," Woodward said.

This protein is called Wzy. It is a sugar polymerase, or an enzyme that interacts with the five-sugar chain to begin the process of linking several five-sugar units together.

Getting this far into the process was important, but the researchers also completed one additional step to define yet another protein's role.

Wzy connected the five-sugar chains, but it did so with no defined limit to the number of five-sugar units involved, a feature that does not match the natural process. On an actual bacterial cell wall, the length of the polysaccharide falls within a relatively narrow range of the number of chains connected.

So the scientists introduced another protein, called Wzz, to the mixture. This protein is known as a "chain length regulator." With this protein in the mix, the lengths of the resulting polysaccharides were confined to a much more narrow range.

"We were able to replicate the exact polysaccharide biosynthetic pathway in vitro, getting the correct lengths," Woodward said. "This is important because now you can begin to look at a whole host of other properties in the system."

The group already started trying to answer one compelling question: whether the two proteins, Wzy and Wzz, have to interact to fully achieve formation of the polysaccharide.

"We've shown in some preliminary results that they do interact, but we haven't determined whether that interaction has any functional relevance," Woodward said.

With this knowledge in hand, researchers now have access to information about how all three parts of the lipopolysaccharide, the large biomolecule on Gram-negative bacteria cell surfaces, is formed. One thing they already knew is that the entire process takes place on an inner membrane and is then exported to the outer membrane on the cell surface.

Now that scientists can reproduce formation of the lipopolysaccharide, they can more directly characterize the export process a step in the pathway that serves as another potential antibiotic target, Woodward noted.


Contact: Robert Woodward
Ohio State University

Related biology news :

1. Scientists discover key step for regulating embryonic development
2. Scientists sever molecular signals that prolific parasite uses to puppeteer cells
3. Scientists create artificial human skin with biomechanical properties using tissue engineering
4. Brown scientists elected to American Academy of Arts and Sciences
5. Scripps Research scientists reveal how genetic mutations may cause type 1 diabetes
6. 2 Hopkins scientists awarded European honorary doctorates
7. Chinese scientists discover marker indicating the developmental potential of stem cells
8. Scientists find new genes for cancer, other diseases in plants, yeast and worms
9. Scripps Research scientists solve mystery of fragile stem cells
10. Ontario Cancer Institute, US scientists discover compound that kills lymphoma cells
11. UTHealth stem cell scientists explore treatments for blood disorders and lung diseases
Post Your Comments:
(Date:10/29/2015)... Calif. , Oct. 29, 2015  The J. ... new report titled, "DNA Synthesis and Biosecurity: Lessons Learned ... the Department of Health and Human Services guidance for ... in 2010. --> ... it also has the potential to pose unique biosecurity ...
(Date:10/29/2015)... Oct. 29, 2015  Connected health pioneer, Joseph ... explosion of technology-enabled health and wellness, and the business ... The Internet of Healthy Things . ... smartphones even existed, Dr. Kvedar, vice president, Connected Health, ... care delivery, moving care from the hospital or doctor,s ...
(Date:10/27/2015)... NEW YORK , Oct. 27, 2015 ... the major issues of concern for various industry verticals ... This is due to the growing demand for secure ... practices in various ,sectors, such as hacking of bank ... concerns for electronic equipment such as PC,s, laptops, and ...
Breaking Biology News(10 mins):
(Date:12/1/2015)... , Dec. 01, 2015 ... addition of the "2016 Europe Cell ... Innovative Technologies, Competitive Strategies, Opportunities for Suppliers--France, ... their offering. --> ) ... "2016 Europe Cell Surface Markers: Country Volume ...
(Date:12/1/2015)... , Dec. 1, 2015  Symic, a clinical-stage biotherapeutics ... extracellular matrix (ECM), today announced that it has secured ... the company,s pipeline, including its lead candidates SB-030 and ... includes the participation by all existing major investors, as ... the total capital raised by Symic to over $43 ...
(Date:12/1/2015)... December 1, 2015 ... the  "2016 U.K. Virology and Bacteriology Testing ... 100 Tests, Supplier Shares by Test, Innovative ... their offering.  --> ) ... U.K. Virology and Bacteriology Testing Market: Sales ...
(Date:11/30/2015)... CHICAGO , Dec. 1, 2015  An interventional radiology ... according to the preliminary results of a study being presented ... North America (RSNA). ... been done for decades by interventional radiologists as a way ... performing the procedure as a means of treating obesity is ...
Breaking Biology Technology: