Research Highlights

Researchers surveyed a database of 4,400 diverse bacterial genomes, using comparative genomics to identify orthologs of MEP and mevalonate pathway genes. In particular, they looked for alternatives to circumvent the IspG and IspH enzymes, which pose known engineering constraints, or to Dxs, for which some alternatives exist.

Researchers identified the sorghum genes responsible for making and breaking down raffinose family oligosaccharides (RFOs) and analyzed their activities in different leaf and stem cell types. The results indicate RFOs are produced in leaf cells responsible for photosynthesis and broken down in veins, releasing sucrose where it can be transported throughout the plant. This suggests that RFOs improve sucrose distribution by enhancing short-distance movement within organs.  

With fewer than 2,000 protein-encoding genes, Zymomonas mobilis has fewer than half the genes of its closest relatives, is good at converting sugar into ethanol, and able to thrive with or without oxygen. This combination of simplicity, efficiency, and versatility make Z. mobilis a promising model for understanding biology and a potential industrial workhorse. Yet the genes required for growth in various conditions have not been well studied.

Despite having the genes needed for respiration, Zymomonas mobilis grows better without oxygen. Even more puzzling, disrupting respiratory genes actually improved its aerobic growth in previous studies, sparking decades of research and debate over the benefits of respiration. Here, scientists showed that Zymomonas uses respiration mainly to lower oxygen levels and protect cells from damage rather than to produce energy.

Muconic acid is a chemical building block that can be used to make plastics such as those used in food and drink packaging, which are typically made from fossil fuels. Here, scientists genetically modified strains of the soil bacterium Novosphingobium aromaticivorans that produce muconic acid from an underused but abundant type of plant fiber called lignin.

Xylose is the second-most abundant sugar in plant biomass. Most yeasts cannot eat xylose even though many have the required genetic pathway. This study showed that gene content is necessary but not sufficient for xylose metabolism and that codon optimization can be a predictor of this trait.

New research shows that one bacterium can be modified to simultaneously produce two valuable compounds from pretreated sorghum biomass: carotenoids, a group of organic pigments used in nutritional supplements, drugs, and cosmetics; and an acid called PDC that can be used to make plastics. The bacteria accumulate carotenoids within their cells, while they secrete PDC from the cells, providing two valuable products that can be easily separated in a single batch. 

Terpenes and variations called terpenoids are chemicals produced by many plants that are responsible for distinctive scents and flavors. Terpenes also serve as signaling molecules that interact with the plant’s environment. GLBRC scientists sought to understand how terpenes and terpenoids affect the bacteria and fungi that live around the roots of two plant species, switchgrass and sorghum.

The study compared the root growth of two plant species in two types of soil to measure the effect of soil pore structure on roots. The findings show for some plants, soil structure plays a privotal role in how their roots grow and how long carbon from the plants remains in the soil.

Understanding epicuticular wax production and identifying the genes that regulate wax loads and composition could enable scientists to engineer more resilient bioenergy crops and improve the economics of biofuel production.