About

Brett Barney is an Associate Professor in the Department of Bioproducts and Biosystems Engineering at the University of Minnesota in the Twin Cities. He serves as the Director of Graduate Studies for the Microbial Engineering (MicE) and Bioproducts and Biosystems, Science Engineering and Management (BBSEM) graduate programs. His educational background includes a B.S. in Chemistry from Utah State University and a Ph.D. in Chemistry and Biochemistry from Arizona State University, where he participated in an interdisciplinary program in biophotonics and conducted research on metalloproteins. His professional experience encompasses six years in industry working in the medical device sector, with roles ranging from analytical chemist to fiber laboratory supervisor. He returned to academia for graduate studies, developing skills in molecular biology, microbiology, genome engineering, and protein chemistry. His postdoctoral work was conducted as a USDA fellow in the laboratory of Professor Lance Seefeldt at Utah State University. He has held positions including Research Assistant Professor and Science Operations Manager at Utah State University before establishing his own laboratory at the University of Minnesota. His research focuses on four primary areas: biosynthetic pathways for producing fuels and high-value chemicals from bacteria and algae, biological nitrogen fixation (BNF) and its role in the nitrogen cycle, extracellular sugar production from phototrophs like algae, and organisms capable of biodegrading plastics and polymers. He teaches courses related to molecular and cellular processes, recycling, environmental microbiology, and seminar series. His laboratory's work involves constructing genetic tools for model bacteria and exploring biosynthetic approaches to replace current fuels and produce specialty chemicals.

Research topics

• Biophysics
• Biochemistry
• Biology
• Chemistry

Selected publications

• Azotobacter vinelandii gene fitness following carbon shift from sucrose to acetate, succinate and glycerol

  Microbiology · 2026-01-16

  articleOpen accessSenior author

  Nitrogen-fixing microbes are a primary contributor of this important nutrient to the global nitrogen cycle. Biological nitrogen fixation (BNF) through the enzyme nitrogenase requires extensive energy that in whole cells is generally studied during the oxidation of carbohydrates such as sugars. The nitrogen-fixing bacterium Azotobacter vinelandii is a model diazotroph for the study of aerobic BNF. Much is known about metabolism in A. vinelandii when cultured on a simple medium where energy is provided primarily in the form of sucrose or glucose. Outside of the laboratory, this soil bacterium grows on metabolites primarily derived from plant root exudates or from the degradation of dead plant matter. In this work, we expand on previous studies looking at genes that are essential to BNF in A. vinelandii when grown on sucrose medium using transposon sequencing (Tn-seq). We applied Tn-seq to determine the genes essential to growth when the medium was shifted to acetate, succinate or glycerol as the primary carbon and energy source to fuel both growth and BNF. A global overview of the genes of central metabolism and those directing substrates toward central metabolism, along with a selection of unexpected genes that were essential for specific growth substrates, is provided.

  PublisherDOI

• Characterising complex metabolic responses in an engineered, cross-feeding microbial co-culture using quantitative proteomics

  New Biotechnology · 2026-02-04

  articleOpen access

  Microbial communities play a key role in biogeochemical transformations in a wide range of ecosystems, but they also hold significant potential to enhance the bioproduction of desired chemicals. Although designing synthetic microbial consortia has generated a lot of interest, a more in-depth understanding of the interactions between strains is required, particularly when strains are engineered to cross-feed, but are not isolated from related environments. Challenges include enhancing stability, productivity and controllability. Here, we used a synthetic microbial co-culture consisting of engineered strains of the photosynthetic cyanobacterium Synechococcus elongatus PCC 7942 cscB/SPS and nitrogen-fixing bacterium Azotobacter vinelandii AV3. Each relies on the other for conversion of atmospheric carbon (CO 2 ) and nitrogen (N 2 ) into organic forms, i.e. sucrose and ammonia, respectively, resources which can be shared. As both strains have such contrasting growth dynamics in co-culture compared to monoculture, we applied a label-free quantitative proteomics approach to characterise metabolism in both strains. The proteomes of both shifted when in co-culture to reflect adaptive restructuring of carbon and nitrogen metabolism, although A. vinelandii appeared to transition to a more stressed state, inducing proteins linked to polymer biosynthesis. An analysis of the co-culture over 16 days led to phenotypic changes, including cell structure alterations in A. vinelandii AV3 over time, with the proteome suggesting cell envelope remodelling and potentially encystment. These findings suggest that physiological control of parameters, such as oxygen and nutrient availability, may enable cultivation of more stable co-cultures. • Quantitative proteome investigation of synthetic microbial co-culture • Cross-feeding of organic carbon and nitrogen • Evidence of specific stress responses in co-culture • Key insights into strategies for process optimization

  PublisherDOI

• A Foundation for Advancing Studies of the Biodegradation of Polyethylene Surrogates by Environmental and Model Laboratory Microbes

  Environmental Microbiology Reports · 2026-03-10

  articleOpen accessSenior authorCorresponding

  Polyethylene represents a particularly recalcitrant class of plastics that persist for decades in the natural environment when released as the result of failed waste management policies. In this report, we present a detailed survey of microbes with varying abilities to degrade either branched or linear waxy hydrocarbons that serve as a surrogate for the study of polyethylene biodegradation. This analysis includes measurement of the degree of branching for the surrogates. We further monitored the growth of individual isolates as an indication of substrate preference. We sequenced the genomes for each of our isolates that showed significant rates of growth to accommodate future biochemical studies, and provide a general characterisation of each strain. The vast majority of microbes that we isolated and identified as part of this study were Actinomycetes. However, a small selection of gram-negative microbes were identified that resulted in degradation of the surrogates. Importantly, our results further identified the model microbes Acinetobacter baylyi and Rhodococcus jostii as strains that were particularly good at degrading all three of the model polyethylene surrogates employed in this study. The results of this study should serve as a detailed genetic and biochemical resource to the research community investigating polyethylene biodegradation.

  PublisherDOI

• Enhanced Urea Production in the Diazotroph <scp> <i>Azotobacter vinelandii</i> </scp> as a Means of Stable Nitrogen Biofertiliser Production

  Microbial Biotechnology · 2025-07-01 · 1 citations

  articleOpen access1st authorCorresponding

  Diazotrophic microbes capture atmospheric nitrogen and convert it into ammonia using the enzyme nitrogenase in a process that provides much of the fixed nitrogen that is required to sustain life in the biosphere. The advent of the Haber Bosch industrial process in the 20th century ushered in an age when agricultural productivity could circumvent the constraints of biological nitrogen fixation, leading to higher productivity based on chemical fertilisers. This industrial process now provides a substantial amount of the nitrogen that we apply to crops, but comes with a large environmental and economic cost. In contrast, biological nitrogen fixation still contributes nitrogen to crops and has the potential to displace some of the industrial nitrogen if we can engineer methods to increase nitrogen levels that are provided to the plant or develop stronger associations between diazotrophs and nonlegume plants. Many of the processes scientists have employed to enhance the nitrogen production by diazotrophs to develop improved biofertilisers have focused on delivering nitrogen in the form of ammonium. In this report, we describe an alternative approach that provides the nitrogen as urea in the form of a terminal product. Using the model diazotroph Azotobacter vinelandii and a three-step approach that deletes the native urease, incorporates a functional arginase and overcomes the feedback inhibition of the arginine biosynthesis pathway, we have increased levels of urea that could be obtained from previous approaches by approximately 43-fold. Our results demonstrate the ability to support the growth of a green alga with these engineered strains and yield total extracellular nitrogen that is comparable to what has been achieved with ammonium.

  PublisherOA PDFDOI

• <i>Azotobacter vinelandii</i> as a Nitrogen‐Negative Chassis for Bio‐Oil and Bio‐Wax Production of Heterologous and Native Lipids

  MicrobiologyOpen · 2025-08-01 · 1 citations

  articleOpen access1st authorCorresponding

  The biosynthetic production of energy-dense petrochemical substitutes is an important goal to address sustainability. The diazotrophic soil microbe Azotobacter vinelandii is a model microbe for the study of biological nitrogen fixation. In addition to capturing atmospheric nitrogen and converting it into usable nitrogen compounds, it is also regarded for the ability to accumulate the bioplastic poly-β-hydroxybutyrate and the extracellular polysaccharide alginate. Here, we demonstrate the potential to broaden the chemical products repertoire of A. vinelandii by demonstrating the accumulation of several classes of biological lipids and waxes. These products include the expanded accumulation of wax esters and fatty alcohols through heterologous expression of foreign genes and pathways, and increased production of the native lipid alkylresorcinol, accomplished by deregulating specific internal pathways and removing competitive pathways for alternative products. As a result, we demonstrate a sevenfold increase in the accumulation of alkylresorcinol, manifesting as intracellular inclusions that are easily extracted with simple solvents and account for nearly 20% of the cellular biomass. By selecting a diazotrophic microbe as a chassis for lipid accumulation, we produced these lipids without any requirement for industrial nitrogen sources in the growth medium, resulting in a net positive nitrogen process as well.

  PublisherOA PDFDOI

• Azotobacter vinelandii

  Trends in Microbiology · 2024-08-20 · 9 citations

  article1st authorCorresponding
  PublisherDOI

• Precision control of ammonium release in <i>Azotobacter vinelandii</i>

  Microbial Biotechnology · 2024-07-01 · 8 citations

  articleOpen access1st authorCorresponding

  The capture and reduction of atmospheric dinitrogen gas to ammonium can be accomplished through the enzyme nitrogenase in a process known as biological nitrogen fixation (BNF), by a class of microbes known as diazotrophs. The diazotroph Azotobacter vinelandii is a model organism for the study of aerobic nitrogen fixation, and in recent years has been promoted as a potential producer of biofertilizers. Prior reports have demonstrated the potential to partially deregulate BNF in A. vinelandii, resulting in accumulation and extracellular release of ammonium. In many cases, deregulation requires the introduction of transgenic genes or elements to yield the desired phenotype, and the long-term stability of these strains has been reported to be somewhat problematic. In this work, we constructed two strains of A. vinelandii where regulation can be precisely controlled without the addition of any foreign genes or genetic markers. Regulation is maintained through native promoters found in A. vinelandii that can be induced through the addition of extraneous galactose. These strains result in varied degrees of regulation of BNF, and as a result, the release of extracellular ammonium is controlled in a precise, and galactose concentration-dependent manner. In addition, these strains yield high biomass levels, similar to the wild-type A. vinelandii strain and are further able to produce high percentages of the bioplastic polyhydroxybutyrate.

  PublisherOA PDFDOI

• A deoxyviolacein‐based transposon insertion vector for pigmented tracer studies

  MicrobiologyOpen · 2024-07-10 · 1 citations

  articleOpen accessSenior authorCorresponding

  Pigments provide a simple means to rapidly visually ascertain the quantities or presence of specific microbes in a complex community. The selection of pigment-producing colonies that are simple to differentiate from common colony phenotypes provides a high degree of certainty for the identity of pigment-tagged strains. Successful employment of pigment production is dependent on various intrinsic factors related to proper levels of gene expression and pigment production that are not always easy to predict and vary within each microbe. We have constructed a simple transposon system that incorporates the genes for the production of deoxyviolacein, a pigment produced from intracellular reserves of the amino acid tryptophan, to randomly insert these genes throughout the genome. This tool allows the user to select from many thousands of potential sites throughout a bacterial genome for an ideal location to generate the desired amount of pigment. We have applied this system to a small selection of endophytes and other model bacteria to differentiate these strains from complex communities and confirm their presence after several weeks in natural environments. We provide two examples of applications using the pigments to trace strains following introduction into plant tissues or to produce a reporter strain for extracellular nitrogen compound sensing. We recognize that this tool could have far broader utility in other applications and microbes, and describe the methodology for use by the greater scientific community.

  PublisherOA PDFDOI

• A polyethylene surrogate for microbial community enrichment and characterization

  Environmental Microbiology · 2024-06-01 · 1 citations

  articleOpen accessSenior authorCorresponding

  Plastic pollution is a vast and increasing problem that has permeated the environment, affecting all aspects of the global food web. Plastics and microplastics have spread to soil, water bodies, and even the atmosphere due to decades of use in a wide range of applications. Plastics include a variety of materials with different properties and chemical characteristics, with polyethylene being a dominant fraction. Polyethylene is also an extremely persistent compound with slow rates of photodegradation or biodegradation. In this study, we developed a method to isolate communities of microbes capable of biodegrading a polyethylene surrogate. This method allows us to study potential polyethylene degradation over much shorter time periods. Using this method, we enriched several communities of microbes that can degrade the polyethylene surrogate within weeks. We also identified specific bacterial strains with a higher propensity to degrade compounds similar to polyethylene. We provide a description of the method, the variability and efficacy of four different communities, and key strains from these communities. This method should serve as a straightforward and adaptable tool for studying polyethylene biodegradation.

  PublisherOA PDFDOI

• Enhanced extracellular ammonium release in the plant endophyte <i>Gluconacetobacter diazotrophicus</i> through genome editing

  Microbiology Spectrum · 2023-12-01 · 10 citations

  articleOpen accessSenior author

  ABSTRACT The plant growth-promoting bacterium Gluconacetobacter diazotrophicus was originally discovered in association with sugarcane plants as an endophyte. As a member of the small class of organisms defined as diazotrophs, G. diazotrophicus is capable of fixing nitrogen from the atmosphere and could serve an important role in minimizing the requirements for nitrogen from industrial-derived fertilizers. In addition to sugarcane, G. diazotrophicus is capable of forming endophyte associations with a variety of other important crops. It has been reported that this microbe requires micro-aerobic conditions to effectively fix nitrogen gas from the atmosphere through the enzyme nitrogenase, making it slightly more difficult to study the diazotrophic lifestyle in the laboratory. The ability of the strain to reside within the plant during growth means that any extracellular nitrogen released by this microbe would immediately become available to the plant host. For this reason, it is an ideal target for development as an improved biofertilizer strain. In this work, we constructed strains of G. diazotrophicus that result in enhanced ammonium release, as measured by growing with a closely associated algal strain under micro-aerobic conditions, and by further quantifying ammonium concentrations accumulated under micro-aerobic and aerobic growth. IMPORTANCE Our results demonstrate increased extracellular ammonium release in the endophyte plant growth-promoting bacterium Gluconacetobacter diazotrophicus . Strains were constructed in a manner that leaves no antibiotic markers behind, such that these strains contain no transgenes. Levels of ammonium achieved by cultures of modified G. diazotrophicus strains reached concentrations of approximately 18 mM ammonium, while wild-type G. diazotrophicus remained much lower (below 50 µM). These findings demonstrate a strong potential for further improving the biofertilizer potential of this important microbe.

  PublisherDOI

Recent grants

• Studies of Neutral Lipid Production in Model Bacteria

  NSF · $300k · 2014–2018

• Bacterial Enzyme Systems for Wax Ester Production

  NSF · $406k · 2009–2013

Frequent coauthors

• Lance C. Seefeldt

  82 shared

• Dennis R. Dean

  Virginia Tech

  74 shared

• Brian M. Hoffman

  Northwestern University

  67 shared

• Tran-Chin Yang

  Northwestern University

  43 shared

• Mikhail Laryukhin

  National Eye Institute

  43 shared

• Robert Y. Igarashi

  University of Central Florida

  37 shared

• Patricia C. Dos Santos

  Wake Forest University

  36 shared

• Hong-In Lee

  Kyungpook National University

  33 shared

Labs

• Barney Bioproducts LabPI

  Not provided

Education

• Doctor of Philosophy, Chemistry and Biochemistry

  Arizona State University

  2003

• Bachelors of Science, Chemistry and Biochemistry

  Utah State University

  1993

Awards & honors

• Distinguished Alumni Award