The biosynthesis of algicides produced by a novelFischerellastrain was investigated. Two allelochemicals were identified, the aminoacylpolyketide fischerellin A (FsA) and the alkaloid 12-epi-hapalindole F (HapF). Based on the structure of FsA, genes that could be involved in its biosynthesis, including those encoding nonribosomal peptide synthetases (NRPSs) and a polyketide synthase (PKS), were identified by the polymerase chain reaction (PCR). By showing that the expression of NRPSs and PKSs is concomitant with algicide production we suggest that the identified genes may be involved in algicide biosynthesis. Analysis of an algicide preparation of the Brazilian-Amazonian strainFischerellasp. CENA 19 revealed the production of FsA,m/z409 (MH+), HapF,m/z370 (MH+), and other potential isoforms of the latter compounds, which were identified by high-performance liquid chromatography (HPLC) and matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) mass-spectrometry. The production of HapF was confirmed after purification by HPLC, analysis by NMR, and high-resolution mass-spectrometry (HRMS). Two-NRPS and a PKS gene were identified after specific amplification using a degenerate PCR. The expression of these synthetases was confirmed by Western blot analysis employing enzyme family-specific antibodies. These analyses revealed the presence of three NRPSs and a single PKS inFischerellasp. CENA 19. The structure of FsA indicates both aminoacyl- and polyketide moeities, suggesting that its biosynthesis may require an integrated NRPS/PKS enzyme system, possibly involving the genes and the synthetases identified. 相似文献
This study investigated the role of a novel metal-dependent catalase (Npun_R4582) that reduces hydrogen peroxide in the cyanobacterium Nostoc punctiforme. Quantitative real-time PCR showed that npun_R4582 relative mRNA levels were upregulated by over 16-fold in cells treated with either 2 μM added Co, 0.5 μM added Cu, 500 μM Mn, 1 μM Ni, or 18 μM Zn. For cells treated with 60 μM H2O2, no significant alteration in Npun_R4582 relative mRNA levels was detected, while in cells treated with Co, Cu, Mn, Ni, or Zn and 60 μM peroxide, relative mRNA levels were generally above control or peroxide only treated cells. Disruption or overexpression of npun_R4582 altered sensitivity to cells exposed to 60 μM H2O2 and metals for treatments beyond the highest viable concentrations, or in a mixed metal solution for Npun_R4582− cells. Moreover, overexpression of npun_R4582 increased cellular peroxidase activity in comparison with wild-type and Npun_R4582− cells, and reduced peroxide levels by over 50%. The addition of cobalt, manganese, nickel, and zinc increased the capacity of Npun_R4582 to reduce the rate or total levels of peroxide produced by cells growing under photooxidative conditions. The work presented confirms the function of NpunR4582 as a catalase and provides insights as to how cells reduce potentially lethal peroxide levels produced by photosynthesis. The findings also show how trace elements play crucial roles as enzymatic cofactors and how the role of Npun_R4582 in hydrogen peroxide breakdown is dependent on the type of metal and the level available to cells.
采用Slater区分单基因和多基因遗传的计算模式及Smith无偏分析方法对21个家系资料的分析表明:利手、优势足、扣手特征均为常染色体单基因显性遗传,R型为显性性状。虽然环境因素对这类特征的表现也有一定的影响,但遗传因素仍起主要作用。
Abstract:The data of 21 families were analyzed by the method of Slater's calculating model to differentiate between single-gene and multi-gene heredity and by the method of non-deviation analysis.The results showed that the hereditary mode of handedness or preferential foot or hand-clasping is the dominant heredity of single gene of autosome,and the right type of all of them is the dominant character.In a way,although environmental factors affected the phenotypes of these characters,hereditary factors were also the decisive ones. 相似文献
The potentially toxic freshwater cyanobacterium Cylindrospermopsis raciborskii has become increasingly prevalent in tropical and temperate water bodies worldwide. This paper investigates the effects of different nitrogen sources (NO3−, NH4+, and omission of a fixed form of nitrogen) on the growth rates, morphologies, and cylindrospermopsin (CYL) concentrations (expressed as a percentage of the freeze-dried weight) of seven C. raciborskii isolates obtained from a range of water bodies in northern Australia and grown in batch culture. In general, growth rates were lowest in the absence of a fixed-nitrogen source and highest with NH4+ as the nitrogen source. Conversely, the highest concentrations of CYL were recorded in cultures grown in the absence of a fixed-nitrogen source and the lowest were found in cultures supplied with NH4+. Cultures supplied with NO3− were intermediate with respect to both CYL concentration and growth rate. Different nitrogen sources resulted in significant differences in the morphology of C. raciborskii trichomes. Most notable were the loss of heterocysts and the tapering of end cells in cultures supplied with NH4+ and the statistically significant increase in vegetative cell length (nitrogen depleted < NO3− < NH4+). The morphological changes induced by different nitrogen sources were consistent for all isolates, despite measurable differences in vegetative-cell and heterocyst dimensions among isolates. Such induced morphological variation has implications for Cylindrospermopsis taxonomy, given that distinctions between species are based on minor and overlapping differences in cell lengths and widths. The close phylogenetic association among all seven isolates was confirmed by the high level (>99.8%) of similarity of their 16S rRNA gene sequences. Another genetic technique, analysis of the HIP1 octameric-palindrome repeated sequence, showed greater heterogeneity among the isolates and appears to be a useful method for distinguishing among isolates of C. raciborskii. 相似文献