Competition between <Emphasis Type="Italic">Lythrum salicaria</Emphasis> and a rare species: combining evidence from experiments and long-term monitoring

The rare endemic plant Sidalcea hendersonii (Henderson’s checker-mallow) occurs in tidal marshes of the Pacific Northwest and may be threatened by Lythrum salicaria (purple loosestrife), a European invader plant. We compared the abundances of Lythrum and Sidalcea in a wetland in British Columbia (Canada) in 1999 to those measured in 1979 to track changes in both species. Although the frequency of Sidalcea decreased by more than 50%, and that of Lythrum increased by almost 20%, there was no significant relationship between the changes of the two species. We assessed the potential effects of competition by Lythrum on Sidalcea in field and patio experiments. In the field, we measured the response of Sidalcea to the removal of Lythrum over a two-year period and compared this to the response of Sidalcea to the removal of native species and in unmanipulated control plots. Removal of Lythrum significantly improved the vegetative performance of Sidalcea compared to the removal of randomly selected native plants and the control treatment in the first year. In the second year, the performance of Sidealcea did not differ significantly with treatment. Removals did not influence the reproductive performance of Sidalcea in either year. A one-year additive experiment, carried out in pots, compared the competitive effect of Lythrum on Sidalcea with that of two native species. Lythrum’s impact on Sidalcea was not consistently stronger than that of the native species. Collectively, these results do not indicate a strong impact of Lythrum on the reproduction or abundance of Sidalcea.     

The Prospect of Purple Non-Sulfur (PNS) Photosynthetic Bacteria for Hydrogen Production: The Present State of the Art

Hydrogen is the fuel for the future, mainly due to its recyclability and nonpolluting nature. Biological hydrogen production processes are operated at ambient temperature and atmospheric pressures, thus are less energy intensive and more environmentally friendly as compared to thermochemical and electrochemical processes. Biohydrogen processes can be broadly classified as: photofermentation and dark fermentation. Two enzymes namely, nitrogenase and hydrogenase play an important role in biohydrogen production. Photofermentation by Purple Non-Sulfur bacteria (PNS) is a major field of research through which the overall yield for biological hydrogen production can be improved significantly by optimization of growth conditions and immobilization of active cells. The purpose of this paper is to review various processes of biohydrogen production using PNS bacteria along with several current developments. However, suitable process parameters such as carbon and nitrogen ratio, illumination intensity, bioreactor configuration and inoculum age may lead to higher yields of hydrogen generation using PNS bacteria.     

Influence of stray capacitance and sample resistance on the kinetics of fast photovoltages from oriented purple membranes

Flash-induced photovoltages were measured with metal electrodes in two experimental systems of purple membranes oriented by an electric field. One system consisted of a suspension of purple membranes cooled to 80 K. The photovoltage evoked by a xenon flash lamp displayed a single phase with a fast rise and a slow RC-decay. The signal shape is consistent with a fast charge separation occurring before the decay of the K-intermediate. The other system consisted of purple membranes embedded and stabilized in polyacrylamide gel. At room temperature, the photovoltage, evoked by a 10 ns laser flash, displayed a negative phase in the submicrosecond range and a slower positive one. The shape of the signals were altered in a complex manner by the stray capacitance and the ionic strength. The rise-time of the negative phase was approx. 14 and approx. 40 ns at ionic strengths of 10 and 1 mM, respectively. The initial peak amplitudes of the photovoltage from both experimental systems depended on the external capacitance in an inverse manner, indicating that both experimental systems were not impedance-matched. The evaluation of kinetic data of molecular reactions from measurements of the photovoltage is discussed.     

Sulfate activation in Rhodobacter sulfidophilus and other species of the Rhodospirillaceae

Rhodobacter sulfidophilus, R. capsulatus, R. sphaeroides, Rhodospirillum rubrum, Rhodopseudomonas palustris, R. viridis and Rhodocyclus gelatinosus were found to be able to synthesize adenylylsulfate and 3-phosphoadenylylsulfate from sulfate and ATP. The presence of ATP sulfurylase was proven for the soluble protein fractions of all these species. ADP sulfurylase was not found. ATP sulfurylase was purified from R. sulfidophilus. Its molecular weight was 290,000. The enzyme is stabilized by magnesium ions and elevated salinities. The optimal pH was 8.0, activity was found between pH 6.8 and 9.4. The enzyme is inactivated at temperatures above 40°C. Kinetic studies resulted in K _m(ATP)=0.26 mM, K _m(sulfate)=0.33 mM; K _i(AMP)-2.1 mM, K _i(ADP)=1.15 mM; K _i(APS)=0.8 M; K _i(sulfite)=0.4. mM; K _i(sulfide)=0.66mM.Uncommon abbreviations APS adenylylsulfate - PAPS 3-phosphoadenylylsulfate - PEP phosphoenolpyruvate Dedicated to Professor Gerhart Drews on the occasion of his 60th birthday     

Association of a new type of gliding,filamentous, purple phototrophic bacterium inside bundles of Microcoleus chthonoplastes in hypersaline cyanobacterial mats

An unidentified filamentous purple bacterium, probably belonging to a new genus or even a new family, is found in close association with the filamentous, mat-forming cyanobacterium Microcoleus chthonoplastes in a hypersaline pond at Guerrero Negro, Baja California Sur, Mexico, and in Solar Lake, Sinai, Egypt. This organism is a gliding, segmented trichome, 0.8–0.9 m wide. It contains intracytoplasmic stacked lamellae which are perpendicular and obliquely oriented to the cell wall, similar to those described for the purple sulfur bacteria Ectothiorhodospira. These bacteria are found inside the cyanobacterial bundle, enclosed by the cyanobacterial sheath. Detailed transmission electron microscopical analyses carried out in horizontal sections of the upper 1.5 mm of the cyanobacterial mat show this cyanobacterial-purple bacterial association at depths of 300–1200 m, corresponding to the zone below that of maximal oxygenic photosynthesis. Sharp gradients of oxygen and sulfide are established during the day at this microzone in the two cyanobacterial mats studied. The close association, the distribution pattern of this association and preliminary physiological experiments suggest a co-metabolism of sulfur by the two-membered community. This probable new genus of purple bacteria may also grow photoheterotrophically using organic carbon excreted by the cyanobacterium. Since the chemical gradients in the entire photic zone fluctuate widely in a diurnal cycle, both types of metabolism probably take place. During the morning and afternoon, sulfide migrates up to the photic zone allowing photoautotrophic metabolism with sulfide as the electron donor. During the day the photic zone is highly oxygenated and the purple bacteria may either use oxidized species of sulfur such as elemental sulfur and thiosulfate in the photoautotrophic mode or grow photoheterotrophically using organic carbon excreted by M. chthonoplastes. The new type of filamentous purple sulfur bacteria is not available yet in pure culture, and its taxonomical position cannot be fully established. This organism is suggested to be a new type of gliding, filamentous, purple phototroph.     

Purification and characterization of the photochemical reaction center of the thermophilic purple sulfur bacterium Chromatium tepidum

Pure reaction center preparations from the thermophilic species Chromatium tepidum have been obtained by lauryldimethylamine N-oxide treatment of chromatophores. The light-induced difference spectrum in presence of 10 mM sodium ascorbate revealed the presence of two high-potential cytochrome c hemes (-band, 555 nm; γ-band, 422 nm). The dithionite-minus-oxidized difference spectrum in the -band suggests the presence of additional hemes of low potential. These hemes are associated with a single polypeptide (M_r = 36 000). The reaction center pigments, probably four bacteriochorophyll a and two bacteriopheophytin a molecules, are associated with three polypeptides of apparent molecular weights equal to 33 000, 30 000 and 22 000. A carotenoid molecule is also bound to the reaction center. The three main absorption bands of this molecule are located at 480, 510 and 530 nm at liquid helium temperature. Photochemical activity is found to be stable, even after heating for 10 min at temperatures higher than 60 °C in intact chromatophore membranes. On the other hand, isolated reaction centers or chromatophores treated with 1% lauryldimethylamine N-oxide are fully inactivated after heating at temperatures higher than 50 °C. From these results, we propose that lipid-protein interactions are of prime importance in the thermal stabilization of Chromatium tepidum reaction centers.     

Evidence for chromophore-chromophore interactions in the Purple Membrane from reconstitution experiments of the chromophore-free membrane

We recently presented evidence showing that the visible CD spectrum of the purple membrane from Halobacterium halobium consists of two contributions: a broad positive band centered at the absorption maximum due to the interaction of the chromophore with the protein to which it is bound, and an exciton coupling band due to the interaction between chromophores of adjacent bacteriorhodopsin molecules in the hexagonal surface lattice (Heyn et al., 1975). This interpretation receives strong support from the present experiments in which the chromophore-free membrane is reconstituted by the addition of retinal. Since the coupling signal arises from the interaction between pairs of neighboring chromophores, its contribution to the spectrum would be expected to be very small in the initial stages of the titration experiment, but increasing quadratically with the percentage reconstitution. The broad positive band, on the other hand, is expected to increase linearly with the percentage reconstitution. On the basis of these considerations a satisfactory explanation of the CD reconstitution experiments could be given. Since it appears to be impossible to explain the titration experiments without the quadratic term, we conclude that chromophore-chromophore interactions play an important role. No significant changes in secondary structure upon reconstitution could be detected consistent with our binding model which neglects cooperativity.Abbreviations CD circular dichroism - UV ultraviolet     

中性红与去离子化紫膜（蓝膜）的相互作用

本文研究了带有正电荷的质子化中性红使去离子化紫膜（蓝膜）再生为紫膜的能力,以及再生紫膜的光化学性质,并从结合中性红的光谱特性中,探讨了结合位的微环境特点,实验结果说明,中性红具有使蓝膜再生为紫膜的能力,但再生紫膜与天然紫膜相比有较慢的光循环速率和较低的质子泵效率,结合至蓝膜上的中性红吸收最大值相对于自由中性红有明显的蓝移,说明了结合中性红是以双体形式存在于亲水环境中,文中讨论了紫膜上金属离子结合位     

一种紫色水稻的遗传及其在光敏不育系育种中应用的研究

研究表明,本院获得的一种紫色水稻的植株色遗传受控于C、 A、Pl3个独立基因座位上显性基因的互补作用,另有一独立的显性基因对Pl基因的表达起抑制作用。由于该抑制基因在籼稻中的高频率存在,因而,紫稻与一般绿稻品种杂交F1多表现为绿株。紫稻光敏不育(株)系的不育性表达和配合力表现,均可达到与普通光敏不育系相似的水平。本文还讨论了选育籼型紫稻光敏不育系设想的可行性。 Abstract:The inheritance of a purple rice in crosses to green rices was investigated.A group of dominant and interactive genes,C,A and Pl,was found to control the expression of the trait and the other independent inhibitor I-Pl-1 to inhibit the effect of the gene Pl.Because of the wide existence of the gene I-Pl-1 in indica rice,most of F1 plants of the crosses between purple rice and green cultivars were green.The primary study indicated that,for the purple photoperiod-sensitive genic male-sterile lines,the degrees of the sterility and its stability in the sterile stage,and of the fertility in the fertile stage,and the combining ability levels of the purple rice were as high as the degrees and levels for the green rice.A tentative idea on breeding purple photoperiod-sensitive male-sterile lines of indica rice was suggested and its feasibility and advantage was discussed.     

Thymidine incorporation in Lake Cisó: Problems in estimating bacterial secondary production across oxic-anoxic interfaces

Abstract Heterotrophic bacterial activity was measured by means of the ³H-thymidine (³H-TdR) incorporation technique in Lake Cisó, a small holomictic lake with anoxic hypolimnion. We tested several methodological questions across the vertical profile: TdR concentration at which maximal incorporation is reached, linearity of incorporation and isotope dilution, during holomixis and stratification periods. The TdR concentration at which maximal incorporation is reached changed seasonally and vertically. During holomixis, maximal incorporation was not always reached at concentrations up to 40 nM. Uptake was always linear in short incubation times and decreased from epi- to hypolimnion. The isotope dilution technique indicated a degree of participation in DNA synthesis higher than 50%, although a linear relationship between the inverse of ³H-TdR incorporation and increasing ‘cold’ thymidine concentration was not always observed. Autoradiographic experiments showed a low percentage of bacteria taking up ³H-TdR in both aerobic and anaerobic samples. The percentage of total labeled bacteria seemed to be generally higher in the metalimnion (11% maximal value) than in the hypolimnion. Labeled Amoebobacter and Chromatium cells were detected in field samples. Amoebobacter cells photoassimilated TdR in culture. Therefore, our results show that ³H-TdR incorporation is not an appropriate technique to estimate bacterial secondary production in anaerobic systems and in oxic-anoxic interfaces.