Single-cell RNA-seq reveals early heterogeneity during aging in yeast.

The budding yeast Saccharomyces cerevisiae (S. cerevisiae) has relatively short lifespan and is genetically tractable, making it a widely used model organism in aging research. Here, we carried out a systematic and quantitative investigation of yeast aging with single-cell resolution through transcriptomic sequencing. We optimized a single-cell RNA sequencing (scRNA-seq) protocol to quantitatively study the whole transcriptome profiles of single yeast cells at different ages, finding increased cell-to-cell transcriptional variability during aging. The single-cell transcriptome analysis also highlighted key biological processes or cellular components, including oxidation-reduction process, oxidative stress response (OSR), translation, ribosome biogenesis and mitochondrion that underlie aging in yeast. We uncovered a molecular marker of FIT3, indicating the early heterogeneity during aging in yeast. We also analyzed the regulation of transcription factors and further characterized the distinctive temporal regulation of the OSR by YAP1 and proteasome activity by RPN4 during aging in yeast. Overall, our data profoundly reveal early heterogeneity during aging in yeast and shed light on the aging dynamics at the single cell level.

[Production and properties of chitinase from Beauveria bassiana Bb174 in solid state fermentation].

This paper studied the chitinase production of Beauveria bassiana Bb174 under solid state fermentation condition. The optimal medium consisted of wheat bran and silkworm chrysalis at the ratio of 4:1, supplemented with 1 g peptone L(-1) as nitrogen source and some other mineral nutrients. The enzyme activity reached 126 units per gram dry medium after cultured for 2 days at 28 degrees C and natural pH by inoculated 3 ml spore suspension into this medium. The optimal temperature and pH for chintinase production were 40 degrees C and 5.0, respectively. The temperature to lose 50% activity of the enzyme was 48 degrees C after incubated at 30-70 degrees C for 1 h. The enzyme was stable at 30-40 degrees C and pH 4-6, and the Km and Vmax values were 0.52 mg x ml(-1) and 0.7 deltaE680 x h(-1), respectively.