Reprioritization of biofilm metabolism is associated with nutrient adaptation and long-term survival of Haemophilus influenzae

Alistair Harrison,Peter White,Sheryl S Justice,Kevin M Mason,Lisa St John-Williams,Rachael L Hardison,Rachel M Wallace,Laura Dubois,J Will Thompson,M Arthur Moseley,Meghan O’ Bryan,Derek R Heimlich,Robert P Sebra,James Fitch

doi:10.1038/s41522-019-0105-6

Abstract

Nontypeable Haemophilus influenzae (NTHI) is a human-restricted pathogen with an essential requirement for heme–iron acquisition. We previously demonstrated that microevolution of NTHI promotes stationary phase survival in response to transient heme–iron restriction. In this study, we examine the metabolic contributions to biofilm formation using this evolved NTHI strain, RM33. Quantitative analyses identified 29 proteins, 55 transcripts, and 31 metabolites that significantly changed within in vitro biofilms formed by RM33. The synthesis of all enzymes within the tryptophan and glycogen pathways was significantly increased in biofilms formed by RM33 compared with the parental strain. In addition, increases were observed in metabolite transport, adhesin production, and DNA metabolism. Furthermore, we observed pyruvate as a pivotal point in the metabolic pathways associated with changes in cAMP phosphodiesterase activity during biofilm formation. Taken together, changes in central metabolism combined with increased stores of nutrients may serve to counterbalance nutrient sequestration.

Highlights

In the wake of the success of the Haemophilus influenzae type b (Hib) vaccine, infections caused by nontypeable H. influenzae (NTHI) strains have increased dramatically, and represent a major cause of otitis media (OM), exacerbations of chronic obstructive pulmonary disease, and bacterial sinusitis
We previously demonstrated that transient depletion of the decreased in RM33 biofilms, suggesting that the preferred essential micronutrient heme–iron increases the longevity of NTHI utilization of serine is for conversion to alanine or malate as an survival in vitro as compared with cultures that were continuously exposed to heme–iron (Fig. 1a; 33)
Aspartate can directly be shuttled into the TCA cycle through conversion to an isolate obtained on day 33 of a long-standing stationary phase culture revealed a single mutation within the icc gene that encodes the only known cAMP phosphodiesterase in NTHI strain 86-028NP.[33]

Summary

Introduction

In the wake of the success of the Haemophilus influenzae type b (Hib) vaccine, infections caused by nontypeable H. influenzae (NTHI) strains have increased dramatically, and represent a major cause of otitis media (OM), exacerbations of chronic obstructive pulmonary disease, and bacterial sinusitis. An innocuous commensal of the nasopharynx, under nutrient stress, viral infection, or other environmental factors, NTHI can become an invasive pathogen. Migration of NTHI from the nasopharynx to the upper and lower respiratory tract coincides with initiation of multiple diseases.[1,2,3,4,5,6,7,8,9] The burden of OM is substantial. Children receive three times more antibiotics than adolescents/adults, with 40% of all antibiotics prescribed for the treatment of OM.[10,11] As a result, the emergence of antibioticresistant strains and the cost associated with managing OM exceeds $5 billion annually in the U.S.12–15 Worldwide, OM is one of the most common indications for outpatient surgery in children,[16] and the most common cause of hearing loss leading to developmental delays in behavior, language, and education.[17,18,19,20]

Methods

Results

Conclusion