New Book Discusses Use of Mass Spectrometry to Identify Microorganisms

FAYETTEVILLE, Ark. — University of Arkansas researchers have edited a book describing ways to identify bacteria using mass spectrometry, a technique that may one day lead to early detection of biological terrorism threats.

Charles L. Wilkins, Distinguished Professor of chemistry and biochemistry, and Jackson O. Lay Jr., director of the University of Arkansas Mass Spectrometry Facility, wrote chapters for and edited the book “Identification of Microorganisms by Mass Spectrometry,” published by John Wiley and Sons Inc. The 15-chapter book provides an overview of the field and the current research in specific areas, including the first portable detection system in use by the military, studies of malaria and the use of different techniques to achieve different results.

The book will help experts from two diverse fields learn more about the other field, enhancing both, Wilkins, a professor in the J. William Fulbright College of Arts and Sciences, said.

“The mass spectrometry researchers need to learn about microbiology and the biologists need to learn the mass spectrometry,” he said.

The time is right for this to happen, Wilkins said, because of advances both in mass spectrometry, allowing researchers to examine samples with higher masses, and advances in computational science, allowing for larger databases, which can contain information on the myriad of proteins found in different bacteria.

After the anthrax outbreak in 2001 when people were exposed to the deadly bacteria through contamination of mail, many researchers seriously began to study rapid methods of bacteria identification. Many bacteria exist in both deadly and benign strains, so tests that identify bacteria must do so down to the strain level. Researchers hope to get at this level by looking at proteins within bacteria and finding proteins unique to each strain.

Mass spectrometry may offer a fast and simple way to identify bacteria. Scientists have started using a technique called matrix-assisted laser desorption/ionization mass spectrometry, known by its acronym, MALDI-MS, to examine bacterial proteins in an attempt to identify bacteria from specific protein markers. One type of MALDI-MS called time-of-flight mass spectrometry, relies on ionizing bacteria, shooting the particles down a tube and measuring the amount of time it takes to go down the tube, then calculating the masses using the time it takes particles of known mass to travel down the tube.

Lay and Rohana Liyanage wrote two chapters on this method: An introduction to MALDI time-of-flight mass spectrometry and MALDI time-of-flight mass spectrometry of intact bacteria. Lay published the first paper on MALDI mass spectrometry on bacteria in 1996 and has done a number of studies in this area since then.

In the book, Wilkins writes about a technique that he pioneered using a unique form of MALDI-MS called Fourier transform mass spectrometry. In this technique, a laser beam ionizes the bacteria, and the ions follow a circular path in a magnetic field, each one cycling at a specific frequency that is directly related to its mass, to its charge and to the magnetic field strength. The researchers can measure frequency with high precision, which allows them to make accurate calculations of protein masses.

The Fourier transform mass spectrometry method has a lower margin of error than many of the current methods of mass spectrometry in use.