The microorganisms that complicate the health of people with cystic fibrosis can survive on little to no oxygen, biologists have found.
In a study of 22 children with cystic fibrosis (CF), the researchers have found new insights into "a spectrum of aerobic and anaerobic lifestyles" of pathogens involved in the disease.
The study sheds light on the conditions under which CF microbes can survive.
Senior co-author Dianne Newman, PhD, professor of biology and geobiology at the California Institute of Technology in Pasadena, explains the context of the research for cystic fibrosis:
"The diversity and adaptation of disease-causing microorganisms within the CF lung environment, in part, is what renders CF infections so difficult to eradicate."
Prof. Newman adds:
"Few studies have attempted to characterize the chemistry of mucus collecting in CF airways, yet such measurements are essential if we are to understand how microorganisms survive in the lung and impact the microenvironment."
Published in the biology journal mBio, the research evaluated the children's sputum samples, finding the microbiologic environment can differ between patients - and even within the same patient at different points in time.
The team also found that a number of samples contained the gas hydrogen sulfide, which reacts with and removes oxygen from the environment.
Patients who had detectable levels of this form of sulfur in their sputum tended to have a lower severity of symptoms.
For the work in the laboratory, the researchers used microsensors normally employed in environmental research to measure "high-resolution profiles of the oxygen and sulfide levels" of the 48 fresh sputum samples from the 22 children with CF, cared for at the Children's Hospital Los Angeles.
The team found that the samples had just a very thin layer of oxygen at the surface, but that most were depleted of oxygen.
"We found oxygen only at the very narrow interface between the air and samples," says senior co-author Wiebke Ziebis, PhD, associate professor of biological sciences at the University of Southern California in Los Angeles.
"It's not only a stratified environment, with different microbial communities at different depths of the sputum, but also temporarily dynamic - there were differences not only between patients but also at different time points for the same patients."
Another finding came from 32 of the samples being sent for culture of dominant CF disease-causing microorganisms - 13 harbored Pseudonomas aeruginosa, 12 showed Staphylococcus aureus, five were positive for both and two had neither.
More research will be needed to determine the clinical relevance of such findings, say the authors - such as whether particular metabolic fingerprints correlate with disease progression and, if so, which treatments would be most effective under these conditions.
Prof. Newman says: "A greater diversity of metabolic survival strategies need to be considered and understood, including ones that operate solely under no-oxygen conditions, because that represents an important reservoir within this habitat."