Biology subjects

Mellies, J.

Publications and source records attributed to Mellies, J..

3 recordsLinked to original sources

bioRxiv2026

Ancestral Hydrocarbon Metabolism Enables PET Degradation by a Natural Bacterial Consortium

Plastic biodegradation in natural environments is increasingly recognized as a multi-organism process, yet the mechanisms enabling coordinated depolymerization and metabolism of polyethylene terephthalate (PET) remain poorly understood. Previously, we demonstrated that a full consortium containing three Pseudomonas and two Bacillus strains isolated from hydrocarbon-rich coastal soils of Galveston Bay, Texas, can synergistically depolymerize PET plastic and utilize it as a sole carbon source, a capacity not observed in individual isolates. In this report, using integrated comparative genomics, proteomics, and chemical analyses, we show that PET degradation in this system reflects exaptation of hydrocarbon metabolism reinforced by metabolic division of labor. Within this naturally occurring consortium, Bacillus strains persist under environmental stress, establish biofilms, and perform essential secondary hydrolysis, while Pseudomonas strains catabolize aromatic monomers and buffer oxidative stress. Genes supporting these functions are enriched within the accessory genomes of the consortium strains, indicating consortium-enriched horizontal gene transfer (HGT). In addition to the canonical two-step hydrolytic pathway well documented in PET biodegradation, we identify a secondary methylation-and redox-associated process, mechanisms where the full consortium acts on the oligomer mono(2-hydroxyethyl) terephthalate (MHET), yielding nearly complete conversion to terephthalic acid (TPA) and methylated MHET (MMHET). Together, these findings demonstrate how cooperation and competition within consortia facilitate targeted gene exchange, enabling emergent plastic biodegradation in natural microbial communities. IMPORTANCEEnvironmental plastic degradation is rarely accomplished by a single organism, yet the microbial mechanisms enabling community-level PET plastic breakdown remain poorly understood. This study shows that a bacterial consortium isolated from crude petroleum-contaminated beaches biodegrades PET through exaptation of ancestral hydrocarbon pathways, metabolic division of labor, and targeted gene exchange rather than specialized PET-specific metabolic pathways. Pseudomonas strains initiate PET cleavage, while stress-tolerant Bacillus strains persist long enough to clear inhibitory intermediates and enable downstream aromatic and diol metabolism. PET degradation is observed to be an emergent property of ecological interactions and distant evolutionary history. These findings provide a community-level model for understanding how natural microbial communities may adapt to novel anthropogenic substrates such as synthetic polymers, sustaining prolonged biodegradation.

microbiology↗

bioRxiv2019

Pseudomonas isolates degrade and form biofilms on polyethylene terephthalate (PET) plastic

Bioaugmentation is a possible remediation strategy for the massive amounts of plastic waste in our oceans and landfills. For this study, soil samples were collected from petroleum polluted locations in the Houston, Texas area to isolate microorganisms capable of plastic degradation. Bacteria were propagated and screened for lipase activity, which has been associated with the bacterial degradation of some plastics to date. We identified three lipase-positive Pseudomonas species, and Bacillus cereus as part of two consortia, which we predict enhances biofilm formation and plastic degradation. Lipase-positive consortia bacteria were incubated alongside blank and E.coli controls with UV-irradiated polyethylene terephthalate (PET), high-density polyethylene (HDPE), or low-density polyethylene (LDPE) as sole sources of carbon. Surface degradation of PET plastic was quantified by changes in molecular vibrations by infrared spectroscopy. The bacteria formed biofilms on PET, observed by scanning electron microscopy, and induced molecular changes on the plastic surface, indicating the initial stages of plastic degradation. We also found molecular evidence that one of the Pseudomonas isolates degrades LDPE. To date, lipase positive Pseudomonas spp. degradation of PET has not been well described, and this work highlights the potential for using consortia of common soil bacteria to degrade plastic waste.

microbiology↗

bioRxiv2018

Isolation and Characterization of a Myoviridae phage that lyses two Escherichia coli pathotypes

PurposeTo identify therapeutic a bacteriophage that kills diarrheagenic enteroaggregative Escherichia coli (EAEC) while leaving the human microbiome intact.\n\nMethodologyPhages from wastewater in Portland, OR, were screened for bacteriolytic activity using an overlay assay, and isolated in a sequential procedure to enrich for the recognition of core bacterial antigens. Electron microscopy and genome sequencing were performed to classify the isolated phage, and the host range was determined by spot tests and plaque assays. One-step growth curves and time-kill assays were conducted to characterize the life cycle of the phage, and to interrogate the multiplicity of infection (MOI) necessary for killing. A mouse model of infection was used to determine whether the phage could be used therapeutically against EAEC in vivo. Anaerobic culture in the presence of human fecal bacteria determined whether the phage could kill EAEC in vitro, and to assess whether the microbiome had been altered.\n\nResultsThe isolated phage, termed Escherichia virus PDX, is a member of the strictly lytic Myoviridae family of viruses. Phage PDX killed EAEC isolate EN1E-0227, a case-associated isolate from a child in rural Tennessee, in a dose-dependent manner, and also formed plaques on case-associated clinical EAEC isolates from Columbian children suffering from diarrhea. A single dose of PDX, at a MOI of 100, one day post infection, reduced the population of recovered EAEC isolate EN1E-0227 bacteria in fecal pellets in a mouse model of colonization, over a five-day period. Phage PDX also killed EAEC EN1E-0227 when cultured anaerobically in vitro in the presence of human fecal bacteria. While the addition of EAEC EN1E-0227 reduced the -diversity of the human microbiota, that of the cultures with either feces alone, feces with EAEC and PDX, or with just the PDX phage were not different statistically, as measured by Chao1 and Shannon diversity indices. Additionally, {beta}-diversity and differential abundance analyses show that conditions with PDX added were not different from feces alone, but all groups were significantly different from feces + EAEC.\n\nConclusionsThe strictly bacteriolytic, Myoviridae Escherichia virus PDX killed EAEC isolate EN1E-0227 bacteria both in vivo and in vitro, while simultaneously not altering the diversity of normal human microbiota in anaerobic culture. Thus, the PDX phage could be part of an effective therapeutic intervention for children in developing countries who suffer from acute, or persistent EAEC-mediated diarrhea, and to help reduce the serious effects of environmental enteropathy. Because the emerging pathogen EAEC is now the second leading cause of travelers diarrhea, PDX could also provide therapeutic relief for these individuals, particularly in light of the growing crisis of antibiotic resistances.

microbiology↗