Molecular ecological network reveals the response of metallurgical microorganisms to energy substrates / 生物工程学报

By analyzing the shift of microbial communities under different iron/sulfur ratios, the response of metallurgical microorganisms to energy substrates was investigated based on molecular ecological networks. High-throughput sequencing of microbial samples from different domesticated batches was conducted to analyze the changes in community composition, alpha and beta diversity. Based on the molecular ecological network, the interactions between microorganisms under different iron/sulfur ratios were explored. Keystones were identified to analyze the community response to energy substrates. In the process of domestication based on different energy substrates, the dominant species in the in iron-rich and sulfur-less community were Acidithiobacillus ferrooxidans and A. ferriphilus. A. thiooxidans accounted for up to 90% in the sulfur-rich and iron-less community after 3 domesticating batches. The results of alpha and beta diversity analysis show that the domestication process of sulfur-rich and iron-less substrates reduced the diversity of microbial communities. Molecular ecological network analysis shows that the keystones were all rare species with low abundance. During the domestication by sulfur-rich and iron-less energy substrates, the bacterial species had a closer symbiotic relationship and the community was more stable. Through this domestication experiment, the impact of different energy substrates on microbial aggregation was clarified. Domesticating metallurgical microorganisms by using sulfur-rich and iron-less energy substrates made the microbial colonies to be more stable, which was conducive to the oxidation of iron and sulfur, promoting the dissolution of sulfide minerals. Our findings provide a reference for the directional domestication of metallurgical microorganisms.

Comparative study of embryo culture media containing and without containing glucose as energy substrate.

The aim to increase pregnancy rate by in vitro fertilization (IVF-ET) is to improve the embryo culture system, especailly the culture media. Most of the conventional IVF media has been deve-loped from somatic cell culture which contains glucose as the energy substrate. Many recent studies in mammals, including human, reported that glucose was not the preferred nutrient for the zygote and early cleaving embryo, and may stimulate premature glycolysis, which induce the Crabtree effect; thus depressing respiratory rate and energy production. This study was conducted to evaluate the embryo culture outcome that grows in conventional IVF media containing 5 mM of glucose (Medicult media) as compared to the home-made media without glucose (SJ-media). Ten infertile couples were enrolled in the study for eleven treatment cycles. Seventy eight oocytes were retrieved, of which sixty three were fertilized as 2 PN embryo, that were randomly allocated into two culture groups: 32 embryos in group I( Medicult media), and 31 embryos in group II (SJ-media). Twenty eight hours after the culture, the embryos in both groups were compared. There was no statistical difference between the embryos of the two culture groups (p>0.05), but there was a trend in which embryos in group I had more 3-4 blastomere than group II (68.8%vs 51.5%); embryos in group II; however; had less fragmentation (67.7% vs 50% for fragmentation< 5%) and were of better quality than group I (51.6% vs 40.6% for embryo grade A, and 32.2% vs 25% for grade B). In conclusion, this study has confirmed that human embryos can grow in media devoid of glucose ; at least; as well as glucose containing media. A larger sample size study ; however ; need to be carried out.

Plasma hormones, blood glucose, free fatty acids and free glycerol responses to moderate exercise after fasting / 体力科学

The present study was carried out to investigate differences in hormonal and metabolic responses to moderate exercise in the post-absorptive state and during a 33-hour fast. Secretory factors and the roles of regulatory hormones of carbohydrate and lipid metabolism during moderate exercise were assessed baesed on these data. Energy substrates in the blood (glucose, BG; lactate, LA; triglyceride, TG; free fatty acids, FFA; free glycerol, FG) and plasma hormones (ACTH; GH; Cortisol, Corti; glucagon, IRG; insulin, IRI) concentrations were measured from 12 h to 33 h during the fasting period (12: 00, 24: 00, 06: 00, 09: 00), and 3min, 10 min and 30min after moderate treadmill exercise (estimated 70-80% of VO<SUB>2</SUB>max) for 20 min under fasting conditions between 09: 00 and 11: 00. These results (in the fasting experiment, Fast) were compared to the results on a normal diet (N-D) .<BR>The results were as follows:<BR>1. No differences in mean VO<SUB>2</SUB> and respiratory exchange ratio (RER) during exercise were observed between the Fast and N-D experiments. Mean heart rate during exercise in Fast was higher by 3.3±2.2 bpm (p<0.05) .<BR>2. Serum FFA and FG concentrations were significantly higher as a results of 24-hour fasting than the values measured at the same time in N-D. No significant change in serum TG concentrations were observed in Fast. While BG and LA concentrations remained low, and in small changes occurred in then both during Fast.<BR>3. Slightly higher levels of plasma ACTH, GH and IRG were found in Fast, but they were not significantly different from N-D. Plasma Corti concentrations gradually increased after 24 hours of fasting, and were 1.9 times higher at 09: 00 after 33 hours of fasting than on N-D. Plasma IRI levels, however, remained low, and the molecular ratio of IRG to IRI (IRG/IRI) was higher throughout Fast (1.8 to 10.6 times higher than on N-D ) .<BR>4. Plasma ACTH, GH and Corti concentrations increased markedly after exercise, and remained high until 30 min on Fast. No significant change in IRG and depression of insulin secretion were demonstrated after exercise on both treatment.<BR>5. Significant correlation between changes in plasma ACTH and Corti concentrations were observed throughout the experiments (Fast, r=0.562; N-D, r=0.528) .<BR>6. All of the energy substrates except blood TG increased after exercise, and the net increases in LA and FG (Δ) on Fast were significantly higher than on N-D. Significant correlations between the changes in the concentrations of FFA and FG (Fast, r=0.745; N-D, r= 0, 696), LA and BG (Fast, r=0.689; N-D, r=0.623), and FFA and LA (Fast, r=0.579; N-D, r= 0.479) were detected throughout both experiments.<BR>7. The coefficients of correlation between changes in plasma ACTH and FFA, and between BG and LA concentrations were higher on Fast than N-D. However, changes in plasma IRI and IRG concentrations were not directly correlated with any other changes in energy substrates in the blood in either treatment.<BR>The results indicated that moderate exercise for 20 min after a 33-hour fast causes marked responses in ACTH, Corti and GH secretions. It appeared that Corti secretion de-pended on ACTH, and that Corti facilitated fatty metabolism during exercise on Fast. However, secretion factors and the role of GH during exercise remain a matter of conjecture.