巢湖富磷地质区沉积物磷的生物可利用性

2010年4-9月,以巢湖富磷地质区池塘为试验对象,测定了叶绿素a与不同形态磷的浓度以及藻类的数量和组成,分析了沉积物藻类可利用性磷(AAP)含量与磷平衡浓度,提取并用分子生物学方法鉴定了沉积物无机磷细菌的主要种类.结果表明,沉积物溶解总磷与AAP含量显著正相关(P＜0.05),与叶绿素a浓度极显著正相关(P＜0.01).沉积物磷在吸附和释放趋势上基本对应于藻类随季节消长的模式.藻的种类较丰富,沉积物无机磷细菌的主要种类包括微单胞菌(Micromonospora sp.,Micromonospora chokoriensis)和链霉菌(Streptomyces neyagawaensis,Streptomyces torulosus).微生物驱动的富磷地质区沉积物磷的溶解可为藻类生长提供生物可利用的磷营养.     

一株光合细菌的分离鉴定及其处理污水能力的研究

[目的]为光合细菌的大规模培养提供技术资料。[方法]从池塘底泥中分离出多株光合细菌,通过分离鉴定,对其中1株生长迅速、各方面性状良好的紫色非硫细菌psb-4进行大规模培养和降解污水试验,并研究pH值及Cu^2＋、Pb^2＋对该菌株净化水质的影响。[结果]psb-4为革兰氏阴性菌,可在光照、厌氧、微好氧条件下生长,适合大规模培养;当温度适宜时,psb-4具有良好的培养特性,培养液中细菌最高浓度超过1.0×10^10个/ml,同时,光照是psb-4生长的重要影响因子;pH值为6-9时,psb-4均具有一定的降解污水中氮、磷的能力,其中pH值为8时,该菌株对氮、磷的降解效果最好;psb-4对Cu^2＋、Pb^2＋具有一定的耐受性,可在重金属污染不严重的污水中应用。[结论]psb-4可在一定pH值和重金属离子浓度范围内降解污水中的氮、磷。     

戊二醛和季铵盐复合消毒剂杀菌效果的试验

将金黄色葡萄球菌、大肠埃希氏菌、溶血性链球菌 C群和类炭疽杆菌实验室培养 ,用 PBS液稀释成 5× 1 0 6 CFU/ m L 细菌悬液或芽胞悬液 ,分别加入到不同浓度的消毒剂作用不同的时间 ,结果表明 :戊二醛和季铵盐复合消毒剂 1∶70 0稀释时 ,1 0 min能有效杀灭金黄色葡萄球菌、大肠埃希氏杆菌、溶血性链球菌 ,1∶ 1 0 0稀释时 ,在 5min可杀灭类炭疽芽胞杆菌。用 1 %浓度的消毒剂对鸡场进行现场消毒 ,结果表明 :该消毒剂在60 min可杀灭 99.96%的细菌     

Reduced dependence of rhizosphere microbiome on plant-derived carbon in 32-year long-term inorganic and organic fertilized soils

Root-derived carbon (C) is considered as critical fuel supporting the interaction between plant and rhizosphere microbiome, but knowledge of how plant–microbe association responds to soil fertility changes in the agroecosystem is lacking. We report an integrative methodology in which stable isotope probing (SIP) and high-throughput pyrosequencing are combined to completely characterize the root-feeding bacterial communities in the rhizosphere of wheat grown in historical soils under three long-term (32-year) fertilization regimes. Wheat root-derived ¹³C was dominantly assimilated by Actinobacteria and Proteobacteria (notably Burkholderiales), accounting for nearly 70% of root-feeding microbiome. In contrast, rhizosphere bacteria utilizing original soil organic matter (SOM) possessed a higher diversity at phylum level. Some microbes (e.g. Bacteroidetes and Chloroflexi) enhancing in the rhizosphere were not actively recruited through selection by rhizodeposits, indicating a limited range of action of root exudates. Inorganic fertilization decreased the dependence of Actinobacteria on root-derived C, but significantly increased its proportion in SOM-feeding microbiome. Furthermore, significantly lower diversity of the root-feeding microbiome, but not the SOM-feeding microbiome, was observed under both organic and inorganic fertilizations. These results revealed that long-term fertilizations with increasing nutrients availability would decrease the preference of rhizosphere microbiome for root-derived substrates, leading to a simpler crop–microbe association.     

Phylogenetic diversity analyses reveal disparity between fungal and bacterial communities during microbial primary succession

Early community assembly of fungi and bacteria differ in many ways, including their contrasting successional trajectories. We examined if fungal and bacterial primary successional dynamics are phylogenetically constrained. Microbial communities were queried across a recently deglaciated forefront using three measures of phylogenetic diversity. We analyzed these data at the Kingdom (fungi) and Domain (bacteria) levels plus at less-inclusive taxonomic hierarchies (Phylum and Class) as well as selected, well-defined functional groups (N-fixing and photosynthetic bacteria). Fungi and bacteria differed in their phylogenetic distributions across successional age. Phylogenetic diversity estimates did not change over successional age for fungi, whereas bacteria were strongly structured phylogenetically over successional age. Further, our results suggest that analyses at Kingdom or Domain levels may prove inadequate to understand successional dynamics. Investigations should include both broad (Kingdom or Domain) and less inclusive groups (perhaps metabolically distinct taxa) to better dissect community dynamics.     

Response of the chitinolytic microbial community to chitin amendments of dune soils

 The dynamics of culturable chitin-degrading microorganisms were studied during a 16-week incubation of chitin-amended coastal dune soils that differed in acidity. Soil samples were incubated at normal (5% w/w) and high (15% w/w) moisture levels. More than half of the added chitin was decomposed within 4 weeks of incubation in most soils. This rapid degradation was most likely due to fast-growing chitinolytic fungi (mainly Mortierella spp. and Fusarium spp.) at both moisture levels, as dense hyphal networks of these fungi were observed during the first 4 weeks of incubation. Chitin N mineralization was inhibited by cycloheximide, and fast-growing fungal isolates were capable of rapid chitin decomposition in sterile sand, further suggesting that these fungi play an important role in initial chitin degradation. The strong increase in fast-growing fungi in chitin-amended dune soils was only detected by direct observation. Plate counts and microscopic quantification of stained hyphae failed to reveal such an increase. During the first part of the incubation, numbers of unicellular chitinolytic bacteria also increased, but their contribution to chitin degradation was indicated to be of minor importance. During prolonged incubation, colony forming units (CFU) of chitinolytic streptomycetes and/or slow-growing fungi increased strongly in several soils, especially at the 5% moisture level. Hence, the general trend observed was a succession from fast-growing fungi and unicellular bacteria to actinomycetes and slow-growing fungi. Yet, the composition of chitinolytic CFU over time differed strongly between chitin-amended dune soils, and also between the two moisture levels. These differences could not be attributed to pH, organic matter or initial microbial composition. The possible consequence of such unpredictable variation in microbial community composition for the use of chitin-amendments as a biocontrol measure is discussed. Received: 10 March 1998     

Short-term changes in amino sugar-specific δ13C values after application of C4 and C3 sucrose

Amino sugars are useful indicators for the accumulation of microbial residues. A 14-day incubation experiment with C4 and C3 sucrose additions was carried out to investigate the relationships between amino sugar-specific shifts in δ¹³C values and those of CO₂ production, microbial biomass C, K₂SO₄ extractable C and soil organic C (SOC). High performance anion exchange chromatography (HPAEC-IRMS) was able to measure amino-sugar specific δ¹³C values for muramic acid (MurN), galactosamine (GalN), and glucosamine (GlcN) in the range of natural abundance. At day 7, the initial application of C4 sucrose significantly increased the δ¹³C value of MurN by 1.0‰ in comparison with the non-amended control treatment, whereas that of GalN and GlcN remained unchanged. This significant increase had disappeared by day 14. This means that the HPAEC-IRMS method is not useful for short-term incubation experiments in the natural abundance range, as the pool size, especially of GalN and GlcN, was too large for a significant response in δ¹³C values. The δ¹³C values significantly decreased in the order MurN (−23.2‰) > GalN (−25.7‰) > GlcN (−26.5‰) in the control treatment. Similar δ¹³C values were measured in GlcN, microbial biomass C, and SOC. MurN exhibited δ¹³C values similar to the K₂SO₄ extractable fraction. These results may be caused by differences in the access of bacteria and fungi to different SOC fractions or differences in metabolic fractionation in bacteria and fungi. C3 sucrose application without further nutrient supply seven days after C4 sucrose application together with N and P led to strong mineralization of freshly formed microbial residues.     

固定化光合细菌去除水中氨氮效果的初步研究

光合细菌固定化是一生物新技术，本文报导了利用这一技术去除水体中氨氮的效果，在运输鲤鱼鱼种中比添加游离光合细菌运输成活率提高10．9％；比对照组成活率提高13．9％。氨氮去除率敞口篓（96．44％），优于密封篓（71％）。本文并对固定化光合细菌在生产实际中的应用前景进行了讨论。