中印度洋与南海西部表层海水细菌多样性

细菌在海洋生物地球化学循环中发挥着重要作用。为更好地了解海洋细菌的特征及其在海洋环境中的潜在作用, 本文利用纯培养与16S rRNA基因高通量测序技术对中印度洋与南海西部海域表层海水细菌多样性进行研究。纯培养结果表明, 自中印度洋与南海西部表层海水中共分离275株可培养海洋细菌, 隶属于4门49属75种。变形菌门是绝对优势类群(占总株数的68.7%), 其次是放线菌门(21.5%)、拟杆菌门(9.1%)和厚壁菌门(0.7%)。在属水平, 微杆菌属(Microbacterium)与弧菌属(Vibrio)是主要的优势属, 共占总株数的30.0%。在3种分离培养基中, 自1/10 × 2216E培养基中分离细菌的数目与种类最多(89株, 30属); 分离菌株中的细菌菌株有7、9与3个属分别仅在2216E、1/10 × 2216E及葡萄糖甘露糖(glucose-mannose, GM)培养基中生长。此外, 共分离培养出50株细菌(26种)可能代表潜在新分类单元。高通量测序结果显示, 中印度洋和南海西部表层海水中共有23个门531个属。优势门类为变形菌门(72.2%)和拟杆菌门(15.3%), 优势属为嗜冷杆菌属(Psychrobacter, 24.4%)、盐单胞菌属(Halomonas, 16.3%)和亚硫酸杆菌属(Sulfitobacter, 13.9%)。此外, 中印度洋表层海水细菌Shannon-Wiener指数与Pielou均匀度指数显著高于南海西部(P < 0.05), 且细菌群落结构显著不同(P < 0.05)。综合纯培养与原位细菌数据得出, 中印度洋与南海西部海洋细菌具有丰富的多样性, 具有进一步开发研究的价值。     

Intracellular K+ sensing of SKOR, a Shaker-type K+ channel from Arabidopsis

Most K+ channels in plants are structurally classified into the Shaker family named after the shaker K+ channel in Drosophila. Plant K+ channels function in many physiological processes including osmotic regulation and K+ nutrition. An outwardly rectifying K+ channel, SKOR, mediates the delivery of K+ from stelar cells to the xylem in the roots, a critical step in the long-distance distribution of K+ from roots to the upper parts of the plant. Here we report that SKOR channel activity is strictly dependent on intracellular K+ concentrations. Activation by K+ did not affect the kinetics of voltage dependence in SKOR, indicating that a voltage-independent gating mechanism underlies the K+ sensing process. Further analysis showed that the C-terminal non-transmembrane region of the SKOR protein was required for this sensing process. The intracellular K+ sensing mechanism couples SKOR activity to K+ nutrition status in the 'source cells', thereby establishing a supply-based unloading system for the regulation of K+ distribution.     

Characterization of microsatellite DNA markers in a critically endangered species,Mekong giant catfish,Pangasianodon gigas

Microsatellite DNA markers for a critically endangered Mekong giant catfish (Pangasianodon gigas Roberts and Vidthayanon, 1991) were developed from fin clips collected from captive fish using (GT)₁₅ probe. The number of alleles per locus ranged from two to four. The expected heterozygosities ranged from 0.13 to 0.68. Also, these primers were successfully amplified in four closely related species, Pangasius bocourti, Pangasius conchophilus, Pangasius larnaudii and Pangasius sanitwongsei with the number of alleles per locus ranged from 1 to 13, 1 to 16, 1 to 12 and 1 to 4, respectively. These markers should prove to be very useful for the evaluation of genetic diversity for this species and other related Pangasius species.     

Bayesian adaptive survey protocols for resource management

Transparency in resource management decisions requires a proper accounting of uncertainty at multiple stages of the decision-making process. As information becomes available, periodic review and updating of resource management protocols reduces uncertainty and improves management decisions. One of the most basic steps to mitigating anthropogenic effects on populations is determining if a population of a species occurs in an area that will be affected by human activity. Species are rarely detected with certainty, however, and falsely declaring a species absent can cause improper conservation decisions or even extirpation of populations. We propose a method to design survey protocols for imperfectly detected species that accounts for multiple sources of uncertainty in the detection process, is capable of quantitatively incorporating expert opinion into the decision-making process, allows periodic updates to the protocol, and permits resource managers to weigh the severity of consequences if the species is falsely declared absent. We developed our method using the giant gartersnake (Thamnophis gigas), a threatened species precinctive to the Central Valley of California, as a case study. Survey date was negatively related to the probability of detecting the giant gartersnake, and water temperature was positively related to the probability of detecting the giant gartersnake at a sampled location. Reporting sampling effort, timing and duration of surveys, and water temperatures would allow resource managers to evaluate the probability that the giant gartersnake occurs at sampled sites where it is not detected. This information would also allow periodic updates and quantitative evaluation of changes to the giant gartersnake survey protocol. Because it naturally allows multiple sources of information and is predicated upon the idea of updating information, Bayesian analysis is well-suited to solving the problem of developing efficient sampling protocols for species of conservation concern. © 2011 The Wildlife Society.     

Senescence induced structural reorganization of thylakoid membranes in Cucumis sativus cotyledons; LHC II involvement in reorganization of thylakoid membranes

We report the formation and appearance of loosely stacked extended grana like structures along with plastoglobuli in the chloroplasts isolated from 27-day old senescing cucumber cotyledons. The origin and the nature of these extended grana structures have not been elucidated earlier. We isolated Photosystem I complexes from 6-day-old control and 27-day-old senescing cotyledons. The chlorophyll a/b ratio of the isolated Photosystem I complex obtained from 6-day cotyledons was 5–5.5 as against a ratio of 2.9 was found in Photosystem I complexes obtained from 27-day-old senescing cotyledons. We also found that the presence of LHC II in the Photosystem I complexes isolated from 27-day cotyledonary chloroplasts. The presence of LHC II in Photosystem I complexes in senescing and not in control samples, clearly suggest the detachment and diffusion of LHC II complexes from stacked grana region to Photosystem I enriched stroma lamellar region thereby, forming loose disorganized extended grana structures seen in the transmission electron microscope. Furthermore, we show that under in vitro condition the senescing cotyledon chloroplasts exhibited lower extent of light induced phosphorylation of LHC II than the control samples suggesting a possible irreversible phosphorylation and diffusion of LHC II in vivo during the progress of senescence in Cucumis cotyledons. From these findings, we suggest that the senescence induced phosphorylation of LHC II and its migration towards Photosystem I may be a programmed one some how causing the destruction of the thylakoid membrane. The released membrane components may be stored in the plastoglobuli prior to their mobilization to the younger plant parts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dominant fungi in the rhizosphere of established tea bushes and their interaction with the dominant bacteria under in situ conditions.

Species of Penicillium and Trichoderma were found to dominate the rhizosphere of established tea bushes in a detailed study conducted from various tea growing locations in India. Penicillium erythromellis, P. janthinellum, P. raistrickii, Trichoderma pseudokoningii and T. koningii were found to be closely associated with tea roots. While seasonal fluctuation was observed in the case of Penicillium spp., the population of Trichoderma spp. showed less variation during the year. Both species were sensitive to low temperatures. In general, fungi associated with the tea rhizosphere were found to prefer a mesophillic temperature range (15 °C to 35 °C). The dominant species of Penicillium and Trichoderma also exhibited tolerance to lower temperatures, i.e., 5 to 10 °C on agar plates. Most fungi were able to grow in a wide range of pH (4 to 12). Lowering of soil pH in the rhizosphere of tea bushes was positively correlated with the age of the bush and may have affected the development of a specific microbial community in the rhizosphere.

The populations of Penicillium and Trichoderma species were inversely correlated with the populations of two most dominant rhizosphere bacteria, Bacillus subtilis and B. mycoides. Both Bacillus species have been shown to have antagonistic activity against these two fungi under in vitro conditions. The present study demonstrates the existence of a similar antagonism under in situ conditions in the rhizosphere of established tea bushes.     

Land, language, and loci: mtDNA in Native Americans and the genetic history of Peru

Despite a long history of complex societies and despite extensive present-day linguistic and ethnic diversity, relatively few populations in Peru have been sampled for population genetic investigations. In order to address questions about the relationships between South American populations and about the extent of correlation between genetic distance, language, and geography in the region, mitochondrial DNA (mtDNA) hypervariable region I sequences and mtDNA haplogroup markers were examined in 33 individuals from the state of Ancash, Peru. These sequences were compared to those from 19 American Indian populations using diversity estimates, AMOVA tests, mismatch distributions, a multidimensional scaling plot, and regressions. The results show correlations between genetics, linguistics, and geographical affinities, with stronger correlations between genetics and language. Additionally, the results suggest a pattern of differential gene flow and drift in western vs. eastern South America, supporting previous mtDNA and Y chromosome investigations.