by James J. Galligan, Ph.D., Associate Chair,
Department of Pharmacology and Toxicology

As described previously,  anti-oxidants from unusual sources (hydrogen sulfide, rotten egg gas) may be helpful in reducing the damage caused by heart attacks and strokes.  The use of hydrogen sulfide produced by the human body as an anti-oxidant illustrates the great lengths we will go to protect ourselves against injury.   A recent study (https://www.sciencemag.org/cgi/content/full/325/5946/1380) published in Science magazine shows that some bacteria are also smart enough to use self produced anti-oxidants to protect them against injury caused by antibiotic drugs.

Nitric Oxide molecule

Nitric Oxide molecule

Nitric oxide (NO) is produced by an enzyme called nitric oxide synthase (NOS).  NOS uses the amino acid L-arginine as the precursor for NO production.  NO is used as a signaling molecule in the nervous system, in blood vessels and by immune cells that use NO to kill invading organisms.  It seems that some bacteria also have their own version of NOS called bacterial NOS (bNOS) that  produces NO from L-arginine.  In addition to its’ role as a signaling molecule in the nervous, cardiovascular and immune systems, NO can act as an anti-oxidant.  NO combines with oxygen radicals reducing the injury that these radicals can cause to cells and tissues.

Nitric Oxide structure (Nitric Oxide at the Chemical Database)

Nitric Oxide structure (Nitric Oxide at the Chemical Database)

What is interesting about bNOS is that many antibiotic drugs kill bacteria by producing oxygen radicals.  Different kinds of bacteria also live in competition with one another.  Bacteria compete for nutrients, and eliminating the competition helps one kind of bacteria survive – at the expense of other bacteria.  Bacteria can generate oxygen radicals to kill off their competitors.  However, the targets of these oxygen radicals have evolved their own anti-oxidant protective mechanism in the form of bNOS and NO production.  NO interacts with oxygen radicals produced by antibiotics and by other bacteria.  This interaction inactivates the oxygen radicals protecting the bacteria against these toxic chemicals.

This is a very interesting study of the biology of bacteria and their interaction with their environment.  The study also provides new insights into how we might best attack bacteria that infect humans, animals and plants.  Perhaps in addition to conventional antibiotic drugs, we could add on an inhibitor of bNOS removing their protection against oxygen radicals.  Treatments for human disease can come from the most unexpected places.  Basic research comes to the rescue again.