The wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici) population in China has been reported to be a distinct genetic group with higher diversity than those in many other countries. Genetic recombination in the P. striiformis f. sp. tritici population has been identified with molecular markers but whether sexual reproduction occurs in China is unknown. In this study, we surveyed barberry plants for infection by rust fungi in the stripe rust "hotspot" regions in Gansu, Sichuan, and Shaanxi provinces; collected barberry plants and inoculated plants of 20 Berberis spp. with germinated teliospores under controlled greenhouse conditions for susceptibility to P. striiformis f. sp. tritici; and tested P. striiformis f. sp. tritici isolates obtained from aecia on naturally infected barberry plants on the wheat genotypes used to differentiate Chinese P. striiformis f. sp. tritici races to determine virulence variations. Different Berberis spp. were widely distributed and most surveyed plants had pycnia and aecia of rust fungi throughout the surveyed regions. In total, 28 Berberis spp. were identified during our study. From 20 Berberis spp. tested with teliospores of P. striiformis f. sp. tritici from wheat plants, 18 species were susceptible under greenhouse conditions. Among 3,703 aecia sampled from barberry plants of three species (Berberis shensiana, B. brachypoda, and B. soulieana) under natural infections in Gansu and Shaanxi provinces, four produced P. striiformis f. sp. tritici uredinia on susceptible wheat 'Mingxian 169'. Sequence of the internal transcribed spacer (ITS) regions of the four isolates from barberry shared 99% identity with the P. striiformis f. sp. tritici sequences in the National Center for Biotechnology Information database. The four isolates had virulence patterns different from all previously reported races collected from wheat plants. Furthermore, 82 single-uredinium isolates obtained from the four barberry isolates had high virulence diversity rates of 9.0 to 28.1%, indicating that the diverse isolates were produced through sexual reproduction on barberry plants under natural conditions. In addition to P. striiformis f. sp. tritici, sequence analysis of polymerase chain reaction products of the ITS regions and inoculation tests on wheat identified P. graminis (the stem rust pathogen). Our results indicated that P. striiformis f. sp. tritici can infect some Berberis spp. under natural conditions, and the sexual cycle of the fungus may contribute to the diversity of P. striiformis f. sp. tritici in China.
The gut harbours diverse and complex microbiota, which influence body health including nutrient metabolism, immune development, and protection from pathogens. Pregnancy is associated with immune and metabolic changes that might be related to microbiota compositional dynamics. We therefore investigated the colonic luminal bacteria community in Huanjiang mini-pigs fed diets with different nutrient levels from the first to third trimester of pregnancy. The concentrations of intestinal metabolites including short-chain fat acids, NH3-N, indole, skatole, and bioamines were also determined. We found that the colonic bacteria species richness estimators (Chao1 and ACE) decreased with increased gestational age. The dominant phyla identified were Firmicutes and Bacteroidetes; the dominant genera were Lactobacillus, Treponema, Ruminococcus, Clostridium, and Prevotella. In addition, microbiota displayed spatial and temporal heterogeneity in composition, diversity, and species abundance in different colonic segments from the first to third trimester of pregnancy. Furthermore, the bacterial metabolites also changed according to the diet used and the pregnancy stage. These findings suggest that colonic bacteria richness decreased as gestational age increased, and that the higher nutrient level diet increased the production of metabolites related to nitrogen metabolism. However, although the higher nutrient diet was associated with pregnancy syndrome, causal links remain to be determined.
Based on the fact that Pichia cell growth follows a Monod equation under the condition of methanol concentration limitation, a kinetics model of recombinant methylotrophic yeast Pichia pastoris expressing porcine insulin precursor (PIP) was developed in the quasi-steady state in the induction phase. The model revealed that the relationship between specific growth rate (µ) and substrate methanol concentration was in accord with the Monod equation. The fermentation kinetic parameters maximum specific growth rate (µ max ), saturation constant (K s ) and maintenance coefficient (M) were estimated to be 0.101 h −1 , 0.252 g l −1 , and 0.011 g MeOH g −1 DCW h −1 , respectively. The unstructured model was validated in methanol induction phase with different initial cell densities. Results showed that the maximum specific protein production rate (q p.max ) of 0.098 mg g −1 DCW h −1 was achieved when µ was kept at 0.016 h −1 , and the maximum yield of PIP reached 0.97 g l −1 , which was 1.5-fold as that of the control. Therefore, the simple Monod model proposed has proven to be a robust control system for recombinant porcine insulin precursor production by P. pastoris on pilot scale, which would be further applied on production scale.
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