Biology subjects

Daran, J.-M. G.

Publications and source records attributed to Daran, J.-M. G..

14 recordsLinked to original sources

bioRxiv2024

Specific growth rates and growth stoichiometries of Saccharomycotina yeasts on ethanol as sole carbon and energy substrate

Emerging low-emission production technologies make ethanol an interesting substrate for yeast biotechnology, but information on growth rates and biomass yields of yeasts on ethanol is scarce. Strains of 52 Saccharomycotina yeasts were screened for growth on ethanol. The 21 fastest strains, among which representatives of the Phaffomycetales order were overrepresented, showed specific growth rates in ethanol-grown shake-flask cultures between 0.12 and 0.46 h-1. Seven strains were studied in aerobic, ethanol-limited chemostats (dilution rate 0.10 h-1). Saccharomyces cerevisiae and Kluyveromyces lactis, whose genomes do not encode Complex-I-type NADH dehydrogenases, showed biomass yields of 0.59 and 0.56 gbiomass g -1, respectively. Different biomass yields were observed among species whose genomes do harbour Complex-I genes: Phaffomyces thermotolerans (0.58 g g-1), Pichia ethanolica (0.59 g g-1), Saturnispora dispora (0.66 g g-1), Ogataea parapolymorpha (0.67 g g-1), and Cyberlindnera jadinii (0.73 g g-1). The biomass yield of C. jadinii, which also showed the highest biomass protein content of these yeasts, corresponded to 88% of the theoretical maximum achieved when growth is limited by assimilation rather than by energy availability. This study indicates that energy coupling of mitochondrial respiration and its regulation are key factors for selecting and improving yeast strains for ethanol-based processes.

microbiology↗

bioRxiv2024

Microbial Electrosynthesis from CO2 reaches Productivity of 1 Syngas and Chain Elongation Fermentations

Microbial electrosynthesis allows the electrochemical upgrading of CO2. However, higher productivities and energy efficiencies are needed to reach a viability that can make the technology transformative. Here we show how a biofilm-based microbial porous cathode in a directed flow-through electrochemical system can continuously reduce CO2 to even-chain C2-C6 carboxylic acids during 248 days. We demonstrate a 3-fold higher biofilm concentration, volumetric current density, and productivity than the state of the art, up to a new record of -35 kA m-3cathode and 69 kgC m-3cathode day-1, at 60-97% and 30-35% faradaic and energy efficiencies, respectively. Most notably, the volumetric productivity resembles those achieved in lab-scale and industrial syngas (CO-H2-CO2) fermentation and chain elongation fermentation. This work highlights key design parameters for efficient electricity-driven microbial CO2 reduction. There is need and room to improve the rates of electrode colonization and microbe-specific kinetics to scale-up the technology. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/579422v1_ufig1.gif" ALT="Figure 1"> View larger version (70K): org.highwire.dtl.DTLVardef@259668org.highwire.dtl.DTLVardef@1b5adedorg.highwire.dtl.DTLVardef@ada588org.highwire.dtl.DTLVardef@4eb23a_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

Long-read direct RNA sequencing of the mitochondrial transcriptome of Saccharomyces cerevisiae reveals condition-dependent intron turnover

Mitochondria fulfil many essential roles and have their own genome, which is expressed as polycistronic transcripts that undergo co- or post-transcriptional processing and splicing. Due to inherent complexity and limited technical accessibility of the mitochondrial transcriptome, fundamental questions regarding mitochondrial gene expression and splicing remain unresolved, even in the model eukaryote Saccharomyces cerevisiae. Long-read sequencing could address these fundamental questions. Therefore, a method for enrichment of mitochondrial RNA and sequencing using Nanopore technology was developed, enabling the resolution of splicing of polycistronic genes and the quantification the spliced RNA. This method successfully captured the full mitochondrial transcriptome and resolved RNA splicing patterns with single-base resolution, and was applied to explore the transcriptome of S. cerevisiae grown with glucose or ethanol as sole carbon source, revealing the impact of growth conditions on mitochondrial RNA-expression and splicing. This study uncovered a remarkable difference in turn-over of group II introns between yeast grown in mostly fermentative and fully respiratory conditions. Whether this accumulation of introns in glucose medium has an impact on mitochondrial functions remains to be explored. Combined with the high tractability of the model yeast S. cerevisiae, the developed method enables to explore mitochondrial transcriptome regulation and processing in a broad range of conditions relevant in human context, including aging, apoptosis and mitochondrial diseases.

microbiology↗

bioRxiv2021

A yeast with muscle does not run faster: full humanization of the glycolytic pathway in Saccharomyces cerevisiae

While transplantation of single genes in yeast plays a key role in elucidating gene functionality in metazoans, technical challenges hamper the humanization of full pathways and processes. Empowered by advances in synthetic biology, this study demonstrates the feasibility and implementation of full humanization of glycolysis in yeast. Single gene and full pathway transplantation revealed the remarkable conservation of both glycolytic and moonlighting functions and, combined with evolutionary strategies, brought to light novel, context-dependent responses. Remarkably, human hexokinase 1 and 2, but not 4, required mutations in their catalytic or allosteric sites for functionality in yeast, while hexokinase 3 was unable to complement its yeast ortholog. Comparison with human tissues cultures showed the preservation of turnover numbers of human glycolytic enzymes in yeast and human cell cultures. This demonstration of transplantation of an entire, essential pathway paves the way to the establishment of species, tissue and disease-specific metazoan models. One Sentence SummaryThis work demonstrates the successful humanization of an entire pathway in Saccharomyces cerevisiae and establishes an attractive strategy to study (human) glycolysis architecture and regulation. HighlightsO_LIThe successful humanization of the entire glycolytic pathway in yeast offers new microbial models for both fundamental and applied studies. C_LIO_LIBoth glycolytic and moonlighting functions and turnover numbers of glycolytic enzymes are highly conserved between yeast and human. C_LIO_LIFunctionality of human hexokinases 1 and 2 in yeast requires mutations in the catalytic or allosteric binding sites. C_LIO_LICombination of single gene and full transplantation with laboratory evolution reveals context-dependent activity and evolution of glycolytic enzymes. C_LI

systems biology↗

bioRxiv2020

Identification of oxygen-independent pathways for pyridine-nucleotide and Coenzyme-A synthesis in anaerobic fungi by expression of candidate genes in yeast

Neocallimastigomycetes are rare examples of strictly anaerobic eukaryotes. This study investigates how these anaerobic fungi bypass reactions involved in synthesis of pyridine nucleotide cofactors and coenzyme A that, in canonical fungal pathways, require molecular oxygen. Analysis of Neocallimastigomycete proteomes identified a candidate L-aspartate-decarboxylase (AdcA), and L-aspartate oxidase (NadB) and quinolinate synthase (NadA), constituting putative oxygen-independent bypasses for coenzyme A synthesis and pyridine nucleotide cofactor synthesis, respectively. The corresponding gene sequences indicated acquisition by ancient horizontal gene transfer event involving bacterial donors. To test whether these enzymes suffice to bypass corresponding oxygen-requiring reactions, they were introduced into fms1Δ and bna2Δ Sacharomyces cerevisiae strains. Expression of nadA and nadB, and adcA from the Neocallimastigomycetes Piromyces finnis and Neocallimastix californiae, respectively, conferred cofactor prototrophy under aerobic and anaerobic conditions. This study simulates how horizontal gene transfer can drive eukaryotic adaptation to anaerobiosis, and provides a basis for elimination of auxotrophic requirements in anaerobic industrial applications of yeasts and fungi.Competing Interest StatementThe authors have declared no competing interest.View Full Text

microbiology↗

bioRxiv2020

gEL DNA, a cloning- and PCR-free method for CRISPR-based multiplexed genome editing

Even for the genetically accessible yeast Saccharomyces cerevisiae, the CRISPR/Cas DNA editing technology has strongly accelerated and facilitated strain construction. Several methods have been validated for fast and highly efficient single editing events and diverse approaches for multiplex genome editing have been described in literature by means of Cas9 or Cas12a endonucleases and their associated gRNAs. The gRNAs used to guide the Cas endonuclease to the editing site are typically expressed from plasmids using native PolII or PolIII RNA polymerases. These gRNA-expression plasmids require laborious, time-consuming cloning steps, which hampers their implementation for academic and applied purposes. In this study, we explore the potential of expressing gRNA from linear DNA fragments using the T7 RNA polymerase (T7RNAP) for single and multiplex genome editing in S. cerevisiae. Using Cas12a, this work demonstrates that transforming short, linear DNA fragments encoding gRNAs in yeast strains expressing T7RNAP promotes highly efficient single DNA editing. These DNA fragments can be custom-ordered, which makes this approach highly suitable for high-throughput strain construction. This work expands the CRISPR-toolbox for large-scale strain construction programs in S. cerevisiae and promises to be relevant for other, less genetically accessible yeast species.Competing Interest StatementThe authors have declared no competing interest.View Full Text

synthetic biology↗

bioRxiv2020

A supernumerary designer chromosome for modular in vivo pathway assembly in Saccharomyces cerevisiae

The construction of microbial cell factories for sustainable production of chemicals and pharmaceuticals requires extensive genome engineering. Using Saccharomyces cerevisiae, this study proposes Synthetic Chromosomes (SynChs) as orthogonal expression platforms for rewiring native cellular processes and implementing new functionalities. Capitalizing the powerful homologous recombination capability of S. cerevisiae, modular SynChs of 50 and 100 Kb were fully assembled de novo from up to 44 transcriptional-unit-sized fragments in a single transformation. These assemblies were remarkably efficient and faithful to their in silico design. SynChs made of non-coding DNA were stably replicated and segregated irrespective of their size without affecting the physiology of their host. These non-coding SynChs were successfully used as landing pad and as exclusive expression platform for the essential glycolytic pathway. This work pushes the limit of DNA assembly in S. cerevisiae and paves the way for de novo designer chromosomes as modular genome engineering platforms in S. cerevisiae.

synthetic biology↗

bioRxiv2020

Adaptive laboratory evolution and reverse engineering of single-vitamin prototrophies in Saccharomyces cerevisiae.

Quantitative physiological studies on Saccharomyces cerevisiae commonly use synthetic media (SM) that contain a set of water-soluble growth factors that, based on their roles in human nutrition, are referred to as B-vitamins. Previous work demonstrated that, in S. cerevisiae CEN.PK113-7D, requirements for biotin could be eliminated by laboratory evolution. In the present study, this laboratory strain was shown to exhibit suboptimal specific growth rates when either inositol, nicotinic acid, pyridoxine, pantothenic acid, para-aminobenzoic acid (pABA) or thiamine were omitted from SM. Subsequently, this strain was evolved in parallel serial-transfer experiments for fast aerobic growth on glucose in the absence of individual B-vitamins. In all evolution lines, specific growth rates reached at least 90 % of the growth rate observed in SM supplemented with a complete B-vitamin mixture. Fast growth was already observed after a few transfers on SM without myo-inositol, nicotinic acid or pABA. Reaching similar results in SM lacking thiamine, pyridoxine or pantothenate required over 300 generations of selective growth. The genomes of evolved single-colony isolates were re-sequenced and, for each B-vitamin, a subset of non-synonymous mutations associated with fast vitamin-independent growth were selected. These mutations were introduced in a non-evolved reference strain using CRISPR/Cas9-based genome editing. For each B-vitamin, introduction of a small number of mutations sufficed to achieve substantially a increased specific growth rate in non-supplemented SM that represented at least 87% of the specific growth rate observed in fully supplemented complete SM. ImportanceMany strains of Saccharomyces cerevisiae, a popular platform organism in industrial biotechnology, carry the genetic information required for synthesis of biotin, thiamine, pyridoxine, para-aminobenzoic acid, pantothenic acid, nicotinic acid and inositol. However, omission of these B-vitamins typically leads to suboptimal growth. This study demonstrates that, for each individual B-vitamin, it is possible to achieve fast vitamin-independent growth by adaptive laboratory evolution (ALE). Identification of mutations responsible for these fast-growing phenotype by whole-genome sequencing and reverse engineering showed that, for each compound, a small number of mutations sufficed to achieve fast growth in its absence. These results form an important first step towards development of S. cerevisiae strains that exhibit fast growth on cheap, fully mineral media that only require complementation with a carbon source, thereby reducing costs, complexity and contamination risks in industrial yeast fermentation processes.

microbiology↗

bioRxiv2019

Young Genes are More Responsive to Environmental Stress than Ancient Genes in Budding Yeasts

The Saccharomycotina subphylum (budding yeasts) spans more than 400 million years of evolution and includes species that thrive in many of Earths harsh environments. Characterizing species that grow in harsh conditions could enable the design of more robust yeast strains for biotechnology. However, tolerance to stressful conditions is a multifactorial response, which is difficult to understand since many of the genes involved are as yet uncharacterized. In this work, three divergent yeast species were grown under multiple stressful conditions to identify stress-induced genes. For each condition, duplicated and non-conserved genes were significantly enriched for stress responsiveness compared to single-copy conserved genes. To understand this further, we developed a sorting method that considers evolutionary origin and duplication timing to assign an evolutionary age to each gene. Subsequent analysis of the sets of genes that changed expression revealed a relationship between stress-induced genes and the youngest gene set, regardless of the species or stress in question. These young genes are rarely essential for growth and evolve rapidly, which may facilitate their functionalization for stress tolerance and may explain their stress-induced expression. These findings show that systems-level analyses that consider gene age can expedite the identification of stress tolerance genes.

systems biology↗

bioRxiv2019

Nanopore sequencing and comparative genome analysis confirm lager-brewing yeasts originated from a single hybridization

BackgroundThe lager brewing yeast, S. pastorianus, is a hybrid between S. cerevisiae and S. eubayanus with extensive chromosome aneuploidy. S. pastorianus is subdivided into Group 1 and Group 2 strains, where Group 2 strains have higher copy number and a larger degree of heterozygosity for S. cerevisiae chromosomes. As a result, Group 2 strains were hypothesized to have emerged from a hybridization event distinct from Group 1 strains. Current genome assemblies of S. pastorianus strains are incomplete and highly fragmented, limiting our ability to investigate their evolutionary history.\n\nResultsTo fill this gap, we generated a chromosome-level genome assembly of the S. pastorianus strain CBS 1483 using MinION sequencing and analysed the newly assembled subtelomeric regions and chromosome heterozygosity. To analyse the evolutionary history of S. pastorianus strains, we developed Alpaca: a method to compute sequence similarity between genomes without assuming linear evolution. Alpaca revealed high similarities between the S. cerevisiae subgenomes of Group 1 and 2 strains, and marked differences from sequenced S. cerevisiae strains.\n\nConclusionsOur findings suggest that Group 1 and Group 2 strains originated from a single hybridization involving a heterozygous S. cerevisiae strain, followed by different evolutionary trajectories. The clear differences between both groups may originate from a severe population bottleneck caused by the isolation of the first pure cultures. Alpaca provides a computationally inexpensive method to analyse evolutionary relationships while considering non-linear evolution such as horizontal gene transfer and sexual reproduction, providing a complementary viewpoint beyond traditional phylogenetic approaches.

bioinformatics↗

bioRxiv2018

Laboratory evolution of a Saccharomyces cerevisiae x S. eubayanus hybrid under simulated lager-brewing conditions: genetic diversity and phenotypic convergence

Saccharomyces pastorianus lager-brewing yeasts are domesticated hybrids of S. cerevisiae x S. eubayanus that display extensive inter-strain chromosome copy number variation and chromosomal recombinations. It is unclear to what extent such genome rearrangements are intrinsic to the domestication of hybrid brewing yeasts and whether they contribute to their industrial performance. Here, an allodiploid laboratory hybrid of S. cerevisiae and S. eubayanus was evolved for up to 418 generations on wort under simulated lager-brewing conditions in six independent sequential batch bioreactors. Characterization of 55 single-cell isolates from the evolved cultures showed large phenotypic diversity and whole-genome sequencing revealed a large array of mutations. Frequent loss of heterozygosity involved diverse, strain-specific chromosomal translocations, which differed from those observed in domesticated, aneuploid S. pastorianus brewing strains. In contrast to the extensive aneuploidy of domesticated S. pastorianus strains, the evolved isolates only showed limited (segmental) aneuploidy. Specific mutations could be linked to calcium-dependent flocculation, loss of maltotriose utilisation and loss of mitochondrial activity, three industrially relevant traits that also occur in domesticated S. pastorianus strains. This study indicates that fast acquisition of extensive aneuploidy is not required for genetic adaptation of S. cerevisiae x S. eubayanus hybrids to brewing environments. In addition, this work demonstrates that, consistent with the diversity of brewing strains for maltotriose utilization, domestication under brewing conditions can result in loss of this industrially relevant trait. These observations have important implications for the design of strategies to improve industrial performance of novel laboratory-made hybrids.

evolutionary biology↗

bioRxiv2018

In vivo recombination of Saccharomyces eubayanus maltose-transporter genes yields a chimeric transporter that enables maltotriose fermentation

Saccharomyces pastorianus lager-brewing yeasts are aneuploid S. cerevisiae x S. eubayanus hybrids, whose genomes have been shaped by domestication in brewing-related contexts. In contrast to most S. cerevisiae and S. pastorianus strains, S. eubayanus cannot utilize maltotriose, a major carbohydrate in brewers wort. Accordingly, S. eubayanus CBS 12357{top} harbors four SeMALT maltose-transporter genes, but no genes resembling the S. cerevisiae maltotriose-transporter gene ScAGT1 or the S. pastorianus maltotriose-transporter gene SpMTY1. To study the evolvability of maltotriose utilization in S. eubayanus CBS 12357{top}, maltotriose-assimilating mutants obtained after UV mutagenesis were subjected to laboratory evolution in carbon-limited chemostat cultures on maltotriose-enriched wort. An evolved strain showed improved maltose and maltotriose fermentation, as well as an improved flavor profile, in 7-L fermenter experiments on industrial wort. Whole-genome sequencing revealed a novel mosaic SeMALT413 gene, resulting from repeated gene introgressions by non-reciprocal translocation of at least three SeMALT genes. The predicted tertiary structure of SeMalt413 was comparable to the original SeMalt transporters, but overexpression of SeMALT413 sufficed to enable growth on maltotriose, indicating gene neofunctionalization had occurred. The mosaic structure of SeMALT413 resembles the structure of S. pastorianus maltotriose-transporter gene SpMTY1, which has sequences with high similarity to alternatingly ScMALx1 and SeMALT3. Evolution of the maltotriose-transporter landscape in hybrid S. pastorianus lager-brewing strains is therefore likely to have involved mechanisms similar to those observed in the present study.\n\nAuthor SummaryFermentation of the wort sugar maltotriose is critical for the flavor profile obtained during beer brewing. The recently discovered yeast Saccharomyces eubayanus is gaining popularity as an alternative to S. pastorianus and S. cerevisiae for brewing, however it is unable to utilize maltotriose. Here, a combination of non-GMO mutagenesis and laboratory evolution of the S. eubayanus type strain CBS 12357{top} was used to enable maltotriose fermentation in brewers wort. A resulting S. eubayanus strain showed a significantly improved brewing performance, including improved maltose and maltotriose consumption and a superior flavor profile. Whole genome sequencing identified a novel transporter gene, SeMALT413, which was formed by recombination between three different SeMALT maltose-transporter genes. Overexpression of SeMALT413 in CBS 12357{top} confirmed its neofunctionalization as a maltotriose transporter. The mosaic structure of the maltotriose transporter SpMty1 in S. pastorianus resembles that of SeMalt413, suggesting that maltotriose utilization likely emerged through similar recombination events during the domestication of current lager brewing strains.

evolutionary biology↗

bioRxiv2018

Allele-specific genome editing using CRISPR-Cas9 causes off-target mutations in diploid yeast

Targeted DNA double-strand breaks (DSBs) with CRISPR-Cas9 have revolutionized genetic modification by enabling efficient genome editing in a broad range of eukaryotic systems. Accurate gene editing is possible with near-perfect efficiency in haploid or (predominantly) homozygous genomes. However, genomes exhibiting polyploidy and/or high degrees of heterozygosity are less amenable to genetic modification. Here, we report an up to 99-fold lower gene editing efficiency when editing individual heterozygous loci in the yeast genome. Moreover, Cas9-mediated introduction of a DSB resulted in large scale loss of heterozygosity affecting DNA regions up to 360 kb that resulted in introduction of nearly 1700 off-target mutations, due to replacement of sequences on the targeted chromosome by corresponding sequences from its non-targeted homolog. The observed patterns of loss of heterozygosity were consistent with homology directed repair. The extent and frequency of loss of heterozygosity represent a novel mutagenic side-effect of Cas9-mediated genome editing, which would have to be taken into account in eukaryotic gene editing. In addition to contributing to the limited genetic amenability of heterozygous yeasts, Cas9-mediated loss of heterozygosity could be particularly deleterious for human gene therapy, as loss of heterozygous functional copies of anti-proliferative and pro-apoptotic genes is a known path to cancer.

molecular biology↗

bioRxiv2017

Nanopore sequencing enables near-complete de novo assembly of Saccharomyces cerevisiae reference strain CEN.PK113-7D

The haploid Saccharomyces cerevisiae strain CEN.PK113-7D is a popular model system for metabolic engineering and systems biology research. Current genome assemblies are based on short-read sequencing data scaffolded based on homology to strain S288C. However, these assemblies contain large sequence gaps, particularly in subtelomeric regions, and the assumption of perfect homology to S288C for scaffolding introduces bias.\n\nIn this study, we obtained a near-complete genome assembly of CEN.PK113-7D using only Oxford Nanopore Technologys MinION sequencing platform. 15 of the 16 chromosomes, the mitochondrial genome, and the 2-micron plasmid are assembled in single contigs and all but one chromosome starts or ends in a telomere cap. This improved genome assembly contains 770 Kbp of added sequence containing 248 gene annotations in comparison to the previous assembly of CEN.PK113-7D. Many of these genes encode functions determining fitness in specific growth conditions and are therefore highly relevant for various industrial applications. Furthermore, we discovered a translocation between chromosomes III and VIII which caused misidentification of a MAL locus in the previous CEN.PK113-7D assembly. This study demonstrates the power of long-read sequencing by providing a high-quality reference assembly and annotation of CEN.PK113-7D and places a caveat on assumed genome stability of microorganisms.

genomics↗