The surprising discovery of different oxygen-18 to oxygen-16 isotope ratios inside versus outside of cells can lead to new frontiers against cancer:
A scientific method that has been used to track the source of illegal drugs, explosives, counterfeit bills and biological warfare agents may have some new uses: detecting rapidly growing cancers and studying obesity and eating disorders…
The researchers found that up to 70 percent of the water inside rapidly growing bacterial cells was generated by metabolism, the process of converting food into energy and other necessities of life. That conclusion was based on their surprising discovery that water inside the bacterial cells (intracellular water) has a different oxygen-18-to-oxygen-16 ratio than water outside the cells (extracellular water).
If future research proves the same thing is true in mammalian cells, then the difference in isotopic makeup of water inside and outside of rapidly growing cells might be used to detect fast-growing cancer cells in the brain or other hard-to-biopsy areas of the body, or study the metabolism of obese people or people suffering anorexia or bulimia, says Hegg, an assistant professor chemistry…
The researchers grew E. coli bacteria at body temperature in flasks containing a nutrient-rich liquid culture medium. There were four sets of flasks, each holding a growth medium containing water with a different ratio of oxygen-18 to oxygen-16.
After the bacteria grew for three hours, the contents of each flask were sucked through a filter, leaving a pasty “cake” of bacterial cells with the consistency of wet flour.
Water was extracted from the bacterial cakes by placing each cake in a test tube, freezing the cakes by putting the tubes in liquid nitrogen, using a vacuum to remove the air from each tube, then putting the tubes in boiling water. The water from each cell cake was boiled into steam, which was routed to another tube where the water condensed.
Before undergoing this process, half of the bacterial cakes were washed with water with four different ratios of oxygen-18 to oxygen-16. The washing process allowed researchers to calculate how much of the water extracted from the bacterial cakes came from outside and from inside the bacteria. Water samples were analyzed in a mass spectrometer, which detects the atomic weights of isotopes of oxygen within the water.
The result: The ratio of oxygen-18 to oxygen-16 was different in water from inside and outside the bacteria. The extent of that difference allowed the scientists to determine that 30 percent of the water inside rapidly growing E. coli came from outside the bacteria and 70 percent of the water was produced by metabolism inside the bacteria.
The research from the University of Utah in Salt Lake City and Pacific Northwest National Laboratory in Richland, Washington was published in the online edition of the Proceedings of the National Academy of Sciences.
More at the University of Utah…