Blake T. Hovde

Nannochloropsis oceanica is a unicellular microalgal eustigmatophyte that is cultivated for industrial applications. N. oceanica grows robustly in open systems, is a rich source of polyunsaturated fatty acids, and has an extensive molecular toolkit, including CRISPR/Cas9 genome editing and transformation. Here, we report the genome assembly of N. oceanica CCAP849/10.

Previous work identified a novel bacterium, FD111, as a likely agent of a Nannochloropsis salina pond infection, demonstrating predatory attributes. Here, we generated a draft genome and identified the bacterium as belonging to the genus Oligoflexus , within the Oligoflexia class.

We present the genome assemblies of two similar Paeniglutamicibacter strains, ORCA_105 and MACA_103, isolated from Mammoth and Oregon Cave systems, respectively. These closely related, but distinct genomes will provide a resource for those studying genomic adaptation to caves.

Summary: Adaptive laboratory evolution (ALE) is a powerful tool to improve phenotypes in microbial cell factories for biotechnological processes. For example, ALE can be utilized to improve growth on alternative carbon sources such as acetate. Acetate is becoming a promising alternative feedstock to produce a variety of bio-products, but growth on acetate is slow relative to other preferred carbon sources and can be toxic to cells. However, ALE in a homogenous environment can lead to evolutionary trade-offs for growth on other carbon sources, which might be detrimental for feedstocks that contain multiple sugars. Here, we evolved Escherichia coli for ∼100 generations using continuous culturing in turbidostats in media containing acetate as the sole carbon source to rapidly select for increased growth in acetate. We measured absolute fitness of 119 clones in acetate and glucose separately to characterize trade-offs and found that trade-off patterns were heterogenous amongst measured clones, with 45% of clones showing significantly reduced growth in glucose. Sequencing revealed that the trade-offs were a result of antagonistic pleiotropic effects of early adaptive mutations, but not all high-effect mutations conferred a trade-off, consistent with the model that mutations accumulated in the selected environment can display a range of pleiotropic effects in other environments. Together, these results suggest that ALE in a homogeneous environment needs to be carefully considered for the improvement of metabolic traits in microbial cells as this could limit the use of evolved strains in complex feedstocks that contain multiple sugars.

The U.S. Department of Energy's Office of Scientific and Technical Information

The majority of pharmaceuticals are derived from natural products, bioactive compounds naturally synthesized by organisms to provide evolutionary advantages. Although the rich evolutionary history of eukaryotic algal species implicates a high potential for natural product-based drug discovery, it remains largely untouched. This study investigates 2762 putative biosynthetic gene clusters (BGCs) from 212 eukaryotic algal genomes. To analyze a vast set of structurally diverse BGCs, we employed comparative analysis based on the vectorization of biosynthetic domains, referred to as biosynthetic domain architecture (BDA). By characterizing core biosynthetic machineries through BDA, we identified key BDAs of modular BGCs in diverse eukaryotes and introduced 16 candidate modular BGCs with similar BDAs to previously validated BGCs. This study provides a global characterization of eukaryotic algal BGCs, offering an alternative to laborious manual curation for BGC prioritization.

Neurodegeneration causes a significant disease burden and there are few therapeutic interventions available for reversing or slowing the disease progression. Induced pluripotent stem cells (iPSCs) hold significant potential since they are sourced from adult tissue and have the capacity to be differentiated into numerous cell lineages, including motor neurons. This differentiation process traditionally relies on cell lineage patterning factors to be supplied in the differentiation media. Genetic engineering of iPSC with the introduction of recombinant master regulators of motor neuron (MN) differentiation has the potential to shorten and streamline cell developmental programs. We have established stable iPSC cell lines with transient induction of exogenous LHX3 and ISL1 from the Tet-activator regulatory region and have demonstrated that induction of the transgenes is not sufficient for the development of mature MNs in the absence of neuron patterning factors. Comparative global transcriptome analysis of MN development from native and Lhx-ISL1 modified iPSC cultures demonstrated that the genetic manipulation helped to streamline the neuronal patterning process. However, leaky gene expression of the exogenous MN master regulators in iPSC resulted in the premature activation of genetic pathways characteristic of the mature MN function. Dysregulation of metabolic and regulatory pathways within the developmental process affected the MN electrophysiological responses.

Despite a continuous increase in algal genome sequencing, structural annotations of most algal genome assemblies remain unavailable. This pervasive scarcity of genome annotation has restricted rigorous investigation of these genomic resources and may have precipitated misleading biological interpretations. However, the annotation process for eukaryotic algal species is often challenging as genomic resources and transcriptomic evidence are not always available. To address this challenge, we benchmark the cutting-edge gene prediction methods that can be generalized for a broad range of non-model eukaryotes. Using the most accurate methods selected based on high-quality algal genomes, we predict structural annotations for 135 unannotated algal genomes. Using previously available genomic data pooled together with new data obtained in this study, we identified the core orthologous genes and the multi-gene phylogeny of eukaryotic algae, including of previously unexplored algal species. This study not only provides a benchmark for the use of structural annotation methods on a variety of non-model eukaryotes, but also compensates for missing data in the current spectrum of algal genomic resources. These results bring us one step closer to the full potential of eukaryotic algal genomics.

The U.S. Department of Energy's Office of Scientific and Technical Information

High-quality genome sequences were generated for the nonaxenic marine microalga Nannochloris desiccata UTEX 2437 and eight of its associated environmental bacterial species. N. desiccata UTEX 2437 is diploid, and its 20.738-Mbp nuclear genome sequence is assembled in 29 contigs.