Postharvest biochemical characteristics and ultrastructure of Coprinus comatus.

BACKGROUND: Coprinus comatus is a novel cultivated edible fungus, hailed as a new preeminent breed of mushroom. However, C. comatus is difficult to keep fresh at room temperature after harvest due to high respiration, browning, self-dissolve and lack of physical protection. METHODS: In order to extend the shelf life of C. comatus and reduce its loss in storage, changes in quality, biochemical content, cell wall metabolism and ultrastructure of C. comatus (C.c77) under 4 °C and 90% RH storage regimes were investigated in this study. RESULTS: The results showed that: (1) After 10 days of storage, mushrooms appeared acutely browning, cap opening and flowing black juice, rendering the mushrooms commercially unacceptable. (2) The activity of SOD, CAT, POD gradually increased, peaked at the day 10, up to 31.62 U g-1 FW, 16.51 U g-1 FW, 0.33 U g-1 FW, respectively. High SOD, CAT, POD activity could be beneficial in protecting cells from ROS-induced injuries, alleviating lipid peroxidation and stabilizing membrane integrity. (3) The activities of chitinase, ß-1,3-glucanase were significantly increased. Higher degrees of cell wall degradation observed during storage might be due to those enzymes' high activities. (4) The fresh C. comatus had dense tissue and every single cell had the number of intracellular organelles which structure can be observed clearly. After 10 d storage, the number of intracellular organelles was declined and the structure was fuzzy, the nucleus disappeared. After 20 d storage, C. comatus's organization was completely lost, many cells were stacked together and the cell wall was badly damaged.

[Genetic diversity of rhizobial bacteria nodulating Tibetia himalaica in eastern Qinghai-Tibet plateau].

OBJECTIVE: Genetic diversity of the rhizobial bacteria nodulating Tibetia himalaica in the eastern part of Qinghai-Tibet Plateau (Ganzi State, Sichuan) were evaluated. METHODS: The pure culture method was used for isolating the rhiobial strains from the nodules. BOXAIR, 16S rDNA sequences, 16S rDNA PCR-RFLP and Principal Component Analysis (PCA) were used to determine the genetic diversity and phylogenetic relationships. The growth in different salt contents, pH and temperatures were tested. RESULTS: In total 22 strains were isolated from 12 samples in 8 counties. The strains tested were classified into 4 clusters in 16S rDNA PCR-RFLP, and 8 clusters were formed in BOXAIR. The 16S rDNA Simpson genetic diversity index was D = 0. 872. The strains tested were closely related to Rhizobium (11/22 strains), Mesorhizobium (4/22 strains) and Rhizobium- Agrobacterium (7/22 strains). All strains could regularly grow in YMA medium amended with 1% NaCl, and 15/22 strains could grow in 4% NaCl. SCAU679, SCAU694 and SCAU706 could adapt to 7% NaCl, while SCAU689 could tolerant 8% NaCl. Among the strains tested, 15 strains could grow in the pH range from 4.0 to 11; 16 isolates grew well from 4 to 45 degrees C, and all of 22 strains could grow at 28 degrees C after treatment at 60 degrees C for 10 min. CONCLUSION: This study revealed the high genetic diversity of the rhizobia isolated from Tibetia himalaica in the eastern part of Qinghai-Tibet Plateau. The strains tested were adapted to high salt, different range of temperatures and pH.

Mesorhizobium sangaii sp. nov., isolated from the root nodules of Astragalus luteolus and Astragalus ernestii.

Our previous published data indicated that the two rhizobial strains SCAU7(T) and SCAU27, which were isolated from the root nodules of Astragalus luteolus and Astragalus ernestii respectively, in Sichuan Province, China, might be novel species of the genus Mesorhizobium. Their exact taxonomic position was determined in the present study by using polyphasic approaches. Comparative analysis of nearly full-length 16S rRNA gene sequences showed that these strains belonged to the genus Mesorhizobium, with Mesorhizobium ciceri USDA 3383(T), Mesorhizobium loti NZP 2213(T), Mesorhizobium shangrilense CCBAU 65327(T) and Mesorhizobium australicum WSM2073(T) as the closest neighbours (>99 % 16S rRNA gene sequence similarity). Phylogenies of the housekeeping genes atpD and recA confirmed their distinct position, showing low similarity with respect to those of M. loti LMG 6125(T) (96.5 % and 92.3 % similarity respectively), M. ciceri USDA 3383(T) (96.8 % and 93.3 % similarity, respectively), M. shangrilense CCBAU 65327(T) (96.5 % and 92.7 % similarity, respectively) and M. australicum WSM2073(T) (95.4 % and 90.6 % similarity, respectively). The DNA-DNA relatedness values between strain SCAU7(T) and strain SCAU27 were 83.0 %, showing that they belong to the same species. The DNA-DNA relatedness values of SCAU7(T) with M. loti NZP 2213(T), M. ciceri USDA 3383(T) and M. shangrilense CCBAU 65327(T) were 41.1 %, 48.8 % and 23.4 %, respectively, clearly indicating that strain SCAU7(T) represents a novel species. A series of phenotypic and genotypic tests and comparison of cellular fatty acids indicated that the novel group of isolates was distinct from previously described species. Therefore, we propose that strains SCAU7(T) and SCAU27 represent a novel species of the genus Mesorhizobium, Mesorhizobium sangaii sp. nov., with strain SCAU7(T) (= HAMBI 3318(T) = ACCC 13218(T)) as the type strain.

[Endophytic bacterial diversity in Codonopsis pilosula, Ephedra sinica, and Lamiophlomis rotate: a study with LH-PCR].

To investigate the endophytic bacterial diversity in the three medicinal plant species Codonopsis pilosula, Ephedra sinica, and Lamiophlomis rotata in Ganzi of Sichuan, Southwest China, the total DNA of the three species were extracted by stringent surface sterilization, and studied with length heterogeneity-PCR (LH-PCR) method. For the same plant species, their root-, stem-, and leaf LH-PCR profiles were in a high level of similarity, with little differences in band richness. However, there existed great differences in the LH-PCR profiles among different plant species. C. pilosula had the biggest band richness, followed by E. sinica, and L. rotata. In the three plant species, the endophytic bacteria with an approximately 474 bp DNA length were dominant. The endophytic bacterial diversity of the plants was negatively correlated with rhizosphere soil available phosphorus content, but positively correlated with rhizosphere soil pH. Elevation and rhizosphere soil total nitrogen content were the important environmental factors affecting the distribution of enophytic bacteria in these plant species. The information of population diversity obtained from LH-PCR could more intuitively reflect the differences of bacterial diversity among different plant species, and thus, LH-PCR would be available to be used for analyzing the endophytic bacterial diversity in medicinal plants, providing information and guidance for the further isolation of microbial resources.

[Screening of antifungi endophytic actinomyces strains from salvia przewalskii in Tibean Plateau].

Twenty-four endophytic actinomycetes strains were isolated from the Salvia przewalskii in Tibetan Plateau of China by tablet coating method. Fusarium moniliforme, Helminthosporium turcicum and Bipolaris maydis were selected as indicator fungi to test the antimicrobial activities of these endophytic actinomycetes by tablet confrontation method. The results showed that 21 strains can produce antimicrobial substances which accounts for 85.7% of the total separates number. Four strains of endogenous actinomyces have more obvious antifungi activity. According to results of morphology and culture properties and 16S rDNA sequences of endophytic actinomyces, it is concluded that all of the isolates were streptomycetes trains.

[Speciation and characterization of interaction of PACls with sulfate].

The interaction of sulfate with various PACl was investigated by using Ferron assay, chemical analysis and SEM. The experimental results showed that the basicity (B = [OH]/[Al]) exhibited significant role in the PACl-sulfate reaction. It indicated different species in various PACl under different reaction pathway with sulfate. The Alc formed precipitation quickly with sulfate, while Alb underwent slowly crystalization. The decrease of Ala resulted in the limit of ferron method. The different speciation component in PACls formed different crystal morphology and chemical composition with sulfate. Increase the basicity, the content of sulfate in precipitate decreased from 0.45 to 0.30.