Many metabolites produced by various microorganisms have proven their usefulness in the area concerning human health. However, most of their diverse natural compound biosyntheses are hardly discovered. These metabolit...Many metabolites produced by various microorganisms have proven their usefulness in the area concerning human health. However, most of their diverse natural compound biosyntheses are hardly discovered. These metabolites might have specific or novel functions and these diverse active compounds can be achieved by biosynthesis, semi-biosynthesis, or chemical synthesis. A strategy to exploit the biosynthesis potential of a fungal strain is to use various culture conditions and to evaluate the chemical profiles of the culture extracts. The value of this approach was demonstrated with the fungal strain Aigialus parvus BCC 5311, producer of hypothemycin, aigialospirol, and aigialomycin A-D. The optimization of hypothemycin production and its derivative diversity by Aigialus parvus BCC 5311 was carried out using qualitative (general factorial design) and quantitative analysis (two-level fractional factorial design). Qualitative analysis revealed that soluble starch and yeast extract were shown to be the best carbon and nitrogen source respectively for the production of hypothemycin, aigialospirol and aigialomycin A-D. Quantitative analysis showed that the initial pH of culture medium is the most important factor that affects the production of hypothemycin and its derivatives (aigialospirol and aigialomycin A-D) production. Optimal medium composition used in a 5 L bioreactor generated a specific growth rate of A. parvus BCC 5311 of 0.0295 h-1, biomass yield of 1.6 g×gstarch-1, hypothemycin yield of 13.6 mg×gbiomass-1, and hypothemycin production rate of 0.6 mg×L-1×day-1. The maximum concentration of 58.0 mg×L-1 of hypothemycin was obtained at 120 h of culturing. Furthermore, the Aigialomycin A-D and Aigialospirol obtained were diversified towards various cultural conditions used. The high amount of hypothemycin produced and the diversity of derivatives obtained from this study should be useful for future mass production.展开更多
Conodonts and ammonoids have played significant roles in the Permian-Triassic timescale.In order to uncover the nature of the Permian-Triassic mass extinction and subsequent recovery,we studied conodont and ammonoid b...Conodonts and ammonoids have played significant roles in the Permian-Triassic timescale.In order to uncover the nature of the Permian-Triassic mass extinction and subsequent recovery,we studied conodont and ammonoid biostratigraphies around the Permian-Triassic boundary from Jianzishan of Hubei,South China.A total of four conodont zones and two ammonoid beds are recognized.In ascending order,the conodont zones are Late Changhsingian Clarkina changxingensis Zone,Clarkina yini Zone and Griesbachian Hindeodus parvus Zone,Hindeodus postparvus Zone;the ammonoid beds are Late Griesbachian Ophiceras beds and Early Dienerian Ussuridiscus varaha beds.At Jianzishan,Ophiceras beds are stratigraphically younger than Hindeodus parvus Zone,but it is likely to be the same level with Hindeodus postparvus Zone.The Lower Dienerian in Bed 8 in this section is characterized by ammonoid Ussuridiscus varaha beds,which is associated with many Late Griesbachian conodonts including Hindeodus postparvus,Hindeodus praeparvus,Hindeodus typicalis,Hindeodus pisai,Hindeodus latidentatus,Hindeodus parvus,Hindeodus anterodentatus and Isarcicella turgida,indicating these conodont species could pass through the Griesbachian-Dienerian boundary and occurred in the Early Dienerian oceans.展开更多
Scatter-hoarding rodents store seeds throughout their home ranges in superficially buried caches which,unlike seeds larder-hoarded in burrows,are difficult to defend.Cached seeds are often pilfered by other scatter-ho...Scatter-hoarding rodents store seeds throughout their home ranges in superficially buried caches which,unlike seeds larder-hoarded in burrows,are difficult to defend.Cached seeds are often pilfered by other scatter-hoarders and either re-cached,eaten or larder-hoarded.Such seed movements can influence seedling recruitment,because only seeds remaining in caches are likely to germinate.Although the importance of scatter-hoarding rodents in the dispersal of western juniper seeds has recently been revealed,the level of pilfering that occurs after initial burial is unknown.Seed traits,soil moisture,and substrate can influence pilfering processes,but less is known about how pilfering varies among caches placed in open versus canopy microsites,or how cache discovery and removal varies among different canopy-types,tree versus shrub.We compared the removal of artificial caches between open and canopy microsites and between tree and shrub canopies at two sites in northeastern California during late spring and fall.We also used trail cameras at one site to monitor artificial cache removal,identify potential pilferers,and illuminate microsite use by scatter-hoarders.Removal of artificial caches was faster in open microsites at both sites during both seasons,and more caches were removed from shrub than tree canopies.California kangaroo rats were the species observed most on cameras,foraging most often in open microsites,which could explain the observed pilfering patterns.This is the first study to document pilfering of western juniper seeds,providing further evidence of the importance of scatter-hoarding rodent foraging behavior in understanding seedling recruitment processes in juniper woodlands.展开更多
文摘Many metabolites produced by various microorganisms have proven their usefulness in the area concerning human health. However, most of their diverse natural compound biosyntheses are hardly discovered. These metabolites might have specific or novel functions and these diverse active compounds can be achieved by biosynthesis, semi-biosynthesis, or chemical synthesis. A strategy to exploit the biosynthesis potential of a fungal strain is to use various culture conditions and to evaluate the chemical profiles of the culture extracts. The value of this approach was demonstrated with the fungal strain Aigialus parvus BCC 5311, producer of hypothemycin, aigialospirol, and aigialomycin A-D. The optimization of hypothemycin production and its derivative diversity by Aigialus parvus BCC 5311 was carried out using qualitative (general factorial design) and quantitative analysis (two-level fractional factorial design). Qualitative analysis revealed that soluble starch and yeast extract were shown to be the best carbon and nitrogen source respectively for the production of hypothemycin, aigialospirol and aigialomycin A-D. Quantitative analysis showed that the initial pH of culture medium is the most important factor that affects the production of hypothemycin and its derivatives (aigialospirol and aigialomycin A-D) production. Optimal medium composition used in a 5 L bioreactor generated a specific growth rate of A. parvus BCC 5311 of 0.0295 h-1, biomass yield of 1.6 g×gstarch-1, hypothemycin yield of 13.6 mg×gbiomass-1, and hypothemycin production rate of 0.6 mg×L-1×day-1. The maximum concentration of 58.0 mg×L-1 of hypothemycin was obtained at 120 h of culturing. Furthermore, the Aigialomycin A-D and Aigialospirol obtained were diversified towards various cultural conditions used. The high amount of hypothemycin produced and the diversity of derivatives obtained from this study should be useful for future mass production.
基金supported by the State Key R&D Project of China(No.2016YFA0601100)the National Natural Science Foundation of China(Nos.41622207,41302271,41530104)the 111 Project(No.B08030)
文摘Conodonts and ammonoids have played significant roles in the Permian-Triassic timescale.In order to uncover the nature of the Permian-Triassic mass extinction and subsequent recovery,we studied conodont and ammonoid biostratigraphies around the Permian-Triassic boundary from Jianzishan of Hubei,South China.A total of four conodont zones and two ammonoid beds are recognized.In ascending order,the conodont zones are Late Changhsingian Clarkina changxingensis Zone,Clarkina yini Zone and Griesbachian Hindeodus parvus Zone,Hindeodus postparvus Zone;the ammonoid beds are Late Griesbachian Ophiceras beds and Early Dienerian Ussuridiscus varaha beds.At Jianzishan,Ophiceras beds are stratigraphically younger than Hindeodus parvus Zone,but it is likely to be the same level with Hindeodus postparvus Zone.The Lower Dienerian in Bed 8 in this section is characterized by ammonoid Ussuridiscus varaha beds,which is associated with many Late Griesbachian conodonts including Hindeodus postparvus,Hindeodus praeparvus,Hindeodus typicalis,Hindeodus pisai,Hindeodus latidentatus,Hindeodus parvus,Hindeodus anterodentatus and Isarcicella turgida,indicating these conodont species could pass through the Griesbachian-Dienerian boundary and occurred in the Early Dienerian oceans.
文摘Scatter-hoarding rodents store seeds throughout their home ranges in superficially buried caches which,unlike seeds larder-hoarded in burrows,are difficult to defend.Cached seeds are often pilfered by other scatter-hoarders and either re-cached,eaten or larder-hoarded.Such seed movements can influence seedling recruitment,because only seeds remaining in caches are likely to germinate.Although the importance of scatter-hoarding rodents in the dispersal of western juniper seeds has recently been revealed,the level of pilfering that occurs after initial burial is unknown.Seed traits,soil moisture,and substrate can influence pilfering processes,but less is known about how pilfering varies among caches placed in open versus canopy microsites,or how cache discovery and removal varies among different canopy-types,tree versus shrub.We compared the removal of artificial caches between open and canopy microsites and between tree and shrub canopies at two sites in northeastern California during late spring and fall.We also used trail cameras at one site to monitor artificial cache removal,identify potential pilferers,and illuminate microsite use by scatter-hoarders.Removal of artificial caches was faster in open microsites at both sites during both seasons,and more caches were removed from shrub than tree canopies.California kangaroo rats were the species observed most on cameras,foraging most often in open microsites,which could explain the observed pilfering patterns.This is the first study to document pilfering of western juniper seeds,providing further evidence of the importance of scatter-hoarding rodent foraging behavior in understanding seedling recruitment processes in juniper woodlands.
