skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Evidence for novel polycyclic aromatic hydrocarbon degradation pathways in culturable marine isolates
ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are common toxic and carcinogenic pollutants in marine ecosystems. Despite their prevalence in these habitats, relatively little is known about the natural microflora and biochemical pathways that contribute to their degradation. Approaches to investigate marine microbial PAH degraders often heavily rely on genetic biomarkers, which requires prior knowledge of specific degradative enzymes and genes encoding them. As such, these biomarker-reliant approaches cannot efficiently identify novel degradation pathways or degraders. Here, we screen 18 marine bacterial strains representing the Pseudomonadota, Bacillota, and Bacteroidota phyla for degradation of two model PAHs, pyrene (high molecular weight) and phenanthrene (low molecular weight). Using a qualitative PAH plate screening assay, we determined that 16 of 18 strains show some ability to degrade either or both compounds. Degradative ability was subsequently confirmed with a quantitative high-performance liquid chromatography approach, where an additional strain showed some degradation in liquid culture. Several members of the prominent marineRoseobacteraceaefamily degraded pyrene and phenanthrene with varying efficiency (1.2%–29.6% and 5.2%–52.2%, respectively) over 26 days. Described PAH genetic biomarkers were absent in all PAH degrading strains for which genome sequences are available, suggesting that these strains harbor novel transformation pathways. These results demonstrate the utility of culture-based approaches in expanding the knowledge landscape concerning PAH degradation in marine systems. IMPORTANCEPolycyclic aromatic hydrocarbon (PAH) pollution is widespread throughout marine environments and significantly affects native flora and fauna. Investigating microbes responsible for degrading PAHs in these environments provides a greater understanding of natural attenuation in these systems. In addition, the use of culture-based approaches to inform bioinformatic and omics-based approaches is useful in identifying novel mechanisms of PAH degradation that elude genetic biomarker-based investigations. Furthermore, culture-based approaches allow for the study of PAH co-metabolism, which increasingly appears to be a prominent mechanism for PAH degradation in marine microbes.  more » « less
Award ID(s):
1737237
PAR ID:
10485508
Author(s) / Creator(s):
;
Editor(s):
Steven, Blaire
Publisher / Repository:
Spectrum
Date Published:
Journal Name:
Microbiology Spectrum
Volume:
12
Issue:
1
ISSN:
2165-0497
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, mSystems)
    Rappe, Michael S. (Ed.)
    ABSTRACT Bacterial biodegradation is a significant contributor to remineralization of polycyclic aromatic hydrocarbons (PAHs)—toxic and recalcitrant components of crude oil as well as by-products of partial combustion chronically introduced into seawater via atmospheric deposition. The Deepwater Horizon oil spill demonstrated the speed at which a seed PAH-degrading community maintained by chronic inputs responds to acute pollution. We investigated the diversity and functional potential of a similar seed community in the chronically polluted Port of Los Angeles (POLA), using stable isotope probing with naphthalene, deep-sequenced metagenomes, and carbon incorporation rate measurements at the port and in two sites in the San Pedro Channel. We demonstrate the ability of the community of degraders at the POLA to incorporate carbon from naphthalene, leading to a quick shift in microbial community composition to be dominated by the normally rare Colwellia and Cycloclasticus . We show that metagenome-assembled genomes (MAGs) belonged to these naphthalene degraders by matching their 16S-rRNA gene with experimental stable isotope probing data. Surprisingly, we did not find a full PAH degradation pathway in those genomes, even when combining genes from the entire microbial community, leading us to hypothesize that promiscuous dehydrogenases replace canonical naphthalene degradation enzymes in this site. We compared metabolic pathways identified in 29 genomes whose abundance increased in the presence of naphthalene to generate genomic-based recommendations for future optimization of PAH bioremediation at the POLA, e.g., ammonium as opposed to urea, heme or hemoproteins as an iron source, and polar amino acids. IMPORTANCE Oil spills in the marine environment have a devastating effect on marine life and biogeochemical cycles through bioaccumulation of toxic hydrocarbons and oxygen depletion by hydrocarbon-degrading bacteria. Oil-degrading bacteria occur naturally in the ocean, especially where they are supported by chronic inputs of oil or other organic carbon sources, and have a significant role in degradation of oil spills. Polycyclic aromatic hydrocarbons are the most persistent and toxic component of crude oil. Therefore, the bacteria that can break those molecules down are of particular importance. We identified such bacteria at the Port of Los Angeles (POLA), one of the busiest ports worldwide, and characterized their metabolic capabilities. We propose chemical targets based on those analyses to stimulate the activity of these bacteria in case of an oil spill in the Port POLA. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Nature Communications)
    Abstract Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, and fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10–100 femtoseconds as a result of beyond-Born-Oppenheimer coupling between the electronic and nuclear dynamics. Here, we investigate three PAH molecules: fluorene, phenanthrene, and pyrene, using ultrafast XUV and IR laser pulses. Simultaneous measurements of the ion yields, ion momenta, and electron momenta as a function of laser pulse delay allow a detailed insight into the various molecular processes. We report relaxation times for the electronically excited PAH * , PAH +* and PAH 2+* states, and show the time-dependent conversion between fragmentation pathways. Additionally, using recoil-frame covariance analysis between ion images, we demonstrate that the dissociation of the PAH 2+ ions favors reaction pathways involving two-body breakup and/or loss of neutral fragments totaling an even number of carbon atoms. 
    more » « less
  3. ; ; ; (, American Geophysical Union)
    Because traditional paleofire archives (e.g., burn scars on trees, charcoal in lake sediments) are not available in all settings, new ways of reconstructing past fire activity are needed. We focus here on polycyclic aromatic hydrocarbons (PAHs) in stalagmites. PAHs are organic molecules composed of two or more fused aromatic rings formed through incomplete combustion of organic matter, and vary in molecular weight depending on combustion conditions. Because the use of PAHs in stalagmites as a paleofire indicator is still in its infancy and because the production, deposition, and transport of PAHs into a cave is a complex and multi-faceted system, we tested the reproducibility of PAHs in two coeval and precisely-dated aragonite stalagmites – KNI-51-F and KNI-51-G - from KNI-51 (15.3°S, 128.6°E), a shallow cave located in the Kimberley region of tropical Western Australia. KNI-51-F and KNI-51-G span 1110-1620 CE and 1310-1630 CE, respectively. Each was hand-milled for analysis in continuous sections spanning approx. 2 mm-tall intervals at Ca’ Foscari University. Owing to differences in growth rate, temporal resolutions for KNI-51-F and KNI-51-G were 3±2 and 1±0.4 yr/sample, respectively. Chemical preparations and analysis methods follow those of Argiriadis et al. (2019) Analytical Chemistry, volume 91. In order to assess replication between the two stalagmites, we compared total abundances of low molecular weight (LMW: Napthalene, Acenaphthylene, Acenaphthene, Fluorene), medium molecular weight (MMW: Phenanthrene, Anthracene, Fluoranthene, Pyrene, Benzo(a)Anthracene, Chrysene, Retene), and high molecular weight (HHM: Benzo(b)Fluoranthene, Benzo(k)Fluoranthene, Benzo(e)Pyrene, Benzo(a)Pyrene, Perylene, Benzo(ghi)Perylene, Indeno(1,2,3-c,d)Pyrene, Dibenzo(A,H)Anthracene) PAHs. Total abundances of LMW, MMW, and HMW PAHs are similar (<10 ng/g) except for HMW PAHs in KNI-51-G, which are generally <1 ng/g. Total LMW and MMW abundance time series replicate well, with multiple synchronous multidecadal periods characterized by consistently low PAH abundances, suggestive of reduced bushfire activity, punctuated by intervals of high PAH abundances, likely reflecting frequent bushfire. Less coherence exists between HMW PAHs. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, Science)
    Polycyclic aromatic hydrocarbons (PAHs) are organic molecules containing adjacent aromatic rings. Infrared emission bands show that PAHs are abundant in space, but only a few specific PAHs have been detected in the interstellar medium. We detected 1-cyanopyrene, a cyano-substituted derivative of the related four-ring PAH pyrene, in radio observations of the dense cloud TMC-1, using the Green Bank Telescope. The measured column density of 1-cyanopyrene is ∼ 1 .52×10 12 cm−2, from which we estimate that pyrene contains up to 0.1% of the carbon in TMC-1. This abundance indicates that interstellar PAH chemistry favors the production of pyrene. We suggest that some of the carbon supplied to young planetary systems is carried by PAHs that originate in cold molecular clouds. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, Physical Chemistry Chemical Physics)
    We investigated the dissociation of dications and trications of three polycyclic aromatic hydrocarbons (PAHs), fluorene, phenanthrene, and pyrene. PAHs are a family of molecules ubiquitous in space and involved in much of the chemistry of the interstellar medium. In our experiments, ions are formed by interaction with 30.3 nm extreme ultraviolet (XUV) photons, and their velocity map images are recorded using a PImMS2 multi-mass imaging sensor. Application of recoil-frame covariance analysis allows the total kinetic energy release (TKER) associated with multiple fragmentation channels to be determined to high precision, ranging 1.94–2.60 eV and 2.95–5.29 eV for the dications and trications, respectively. Experimental measurements are supported by Born–Oppenheimer molecular dynamics (BOMD) simulations. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email