Starvation of yeast cultures limited by auxotrophic requirements results in glucose wasting and failure to achieve prompt cell-cycle arrest when compared with starvation for basic natural nutrients like phosphate or sulfate. We measured the survival of yeast auxotrophs upon starvation for different nutrients and found substantial differences: When deprived of leucine or uracil, viability declined exponentially with a half-life of <2 days, whereas when the same strains were deprived of phosphate or sulfate, the half-life was Ϸ10 days. The survival rates of nongrowing auxotrophs deprived of uracil or leucine depended on the carbon source available during starvation, but were independent of the carbon source during prior growth. We performed an enrichment procedure for mutants that suppress lethality during auxotrophy starvation. We repeatedly found loss-of-function mutations in a number of functionally related genes. Mutations in PPM1, which methylates protein phosphatase 2A, and target of rapamycin (TOR1) were characterized further. Deletion of PPM1 almost completely suppressed the rapid lethality and substantially suppressed glucose wasting during starvation for leucine or uracil. Suppression by a deletion of TOR1 was less complete. We suggest that, similar to the Warburg effect observed in tumor cells, starving yeast auxotrophs wastes glucose as a consequence of the failure of conserved growth control pathways. Furthermore, we suggest that our results on condition-dependent chronological lifespan have important implications for the interpretation and design of studies on chronological aging. auxotrophy starvation ͉ chronological aging ͉ Warburg effect

Haplotype-resolved genomes equencing enables accurate interpretation of medically relevant genetic variation, deep inferences regarding population history, and the non-invasive prediction of fetal genomes. We describe an approach for genome-wide haplotyping based on contiguity preserving transposition (CPT-Seq) and combinatorial indexing. Tn5 transposition is used to modify DNA with adapter and index sequences while preserving contiguity. After dilution and compartmentalization, the transposase is removed, resolving the DNA into individually indexed libraries. The libraries in each compartment, enriched for neighboring genomic elements, are further indexed via PCR. Combinatorial 96-plex indexing at both the transposition and PCR stage enables the construction of phased synthetic reads from each of the nearly 10,000 “virtual compartments”. We demonstrate feasibility of this method by assembling >95% of heterozygous variants in a human genome into long, accurate haplotype blocks (N50 = 1.4–2.3 Mb). The rapid, scalable, and cost-effective workflow could enable haplotype resolution to become routine in human genome sequencing.

We have designed an experimental/computational framework for studying complex phenotypes in bacteria.Our framework relies on whole-genome fitness profiling coupled with a module-level analysis to discover pathways that directly affect fitness.As a proof-of-principle, we studied ethanol tolerance in Escherichia coli and we identified key pathways that contribute to this phenotype.We then validated our findings through genetic manipulations, gene-expression profiling, metabolite-level measurements, and stable-isotope labeling.

We describe a method that exploits contiguity preserving transposase sequencing (CPT-seq) to facilitate the scaffolding of de novo genome assemblies. CPT-seq is an entirely in vitro means of generating libraries comprised of 9216 indexed pools, each of which contains thousands of sparsely sequenced long fragments ranging from 5 kilobases to >1 megabase. These pools are “subhaploid,” in that the lengths of fragments contained in each pool sums to ∼5% to 10% of the full genome. The scaffolding approach described here, termed fragScaff, leverages coincidences between the content of different pools as a source of contiguity information. Specifically, CPT-seq data is mapped to a de novo genome assembly, followed by the identification of pairs of contigs or scaffolds whose ends disproportionately co-occur in the same indexed pools, consistent with true adjacency in the genome. Such candidate “joins” are used to construct a graph, which is then resolved by a minimum spanning tree. As a proof-of-concept, we apply CPT-seq and fragScaff to substantially boost the contiguity of de novo assemblies of the human, mouse, and fly genomes, increasing the scaffold N50 of de novo assemblies by eight- to 57-fold with high accuracy. We also demonstrate that fragScaff is complementary to Hi-C-based contact probability maps, providing midrange contiguity to support robust, accurate chromosome-scale de novo genome assemblies without the need for laborious in vivo cloning steps. Finally, we demonstrate CPT-seq as a means of anchoring unplaced novel human contigs to the reference genome as well as for detecting misassembled sequences.

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