Crystal structure of the flavin-dependent thymidylate synthase Thy1 from Thermus thermophilus with an extra C-terminal domain

Distribution of soil viruses across China and their potential role in phosphorous metabolism

BACKGROUND

Viruses are the most abundant biological entities on the planet and drive biogeochemical cycling on a global scale. Our understanding of biogeography of soil viruses and their ecological functions lags significantly behind that of Bacteria and Fungi. Here, a viromic approach was used to investigate the distribution and ecological functions of viruses from 19 soils across China.

RESULTS

Soil viral community were clustered more significantly by geographical location than type of soil (agricultural and natural). Three clusters of viral communities were identified from North, Southeast and Southwest regions; these clusters differentiated using taxonomic composition and were mainly driven by geographic location and climate factors. A total of 972 viral populations (vOTUs) were detected spanning 23 viral families from the 19 viromes. Phylogenetic analyses of the phoH gene showed a remarkable diversity and the distribution of viral phoH genes was more dependent on the environment. Notably, five proteins involved in phosphorus (P) metabolism-related nucleotide synthesis functions, including dUTPase, MazG, PhoH, Thymidylate synthase complementing protein (Thy1), and Ribonucleoside reductase (RNR), were mainly identified in agricultural soils.

CONCLUSIONS

The present work revealed that soil viral communities were distributed across China according to geographical location and climate factors. In addition, P metabolism genes encoded by these viruses probably drive the synthesis of nucleotides for their own genomes inside bacterial hosts, thereby affecting P cycling in the soil ecosystems.

Boosting Auto-Induction of Recombinant Proteins in Escherichia coli with Glucose and Lactose Additives

BACKGROUND

Auto-induction is a convenient way to produce recombinant proteins without inducer addition using lac operon-controlled Escherichia coli expression systems. Auto-induction can occur unintentionally using a complex culture medium prepared by mixing culture substrates. The differences in culture substrates sometimes lead to variations in the induction level.

OBJECTIVES

In this study, we investigated the feasibility of using glucose and lactose as boosters of auto-induction with a complex culture medium.

METHODS

First, auto-induction levels were assessed by quantifying recombinant GFPuv expression under the control of the T7 lac promoter. Effectiveness of the additive-containing medium was examined using ovine angiotensinogen (tac promoter-based expression) and Thermus thermophilus manganese-catalase (T7 lac promoter-based expression).

RESULTS

Auto-induced GFPuv expression was observed with the enzymatic protein digest Polypepton, but not with another digest tryptone. Regardless of the type of protein digest, supplementing Terrific Broth medium with glucose (at a final concentration of 2.9 g/L) and lactose (at a final concentration of 7.6 g/L) was successful in obtaining an induction level similar to that achieved with a commercially available auto-induction medium. The two recombinant proteins were produced in milligram quantity of purified protein per liter of culture.

CONCLUSION

The medium composition shown in this study would be practically useful for attaining reliable auto-induction for E. coli-based recombinant protein production.