Electrophoretic protein profile of nodulated and non-nodulated Cassia species in relation to taxonomy

The electrophoretic protein profile of the seeds of Cassia species agrees their placement according to the Bentham and Hooker system. There is a definite relationship between nodulated species and some proteins are found only in them. However, it seems that nodulation and proteins do not agree exactly and nodulation cannot be used as a good criterion for phylogenetic relationships between Cassia species.     

Schistosoma mansoni and Schistosoma haematobium: Differences in development

Growth and maturation of the Puerto Rico strain of Schistosoma mansoni in mice and the Ghana strain of Schistosoma haematobium in hamsters were compared beginning 19 days after infection. In S. mansoni, optimum development was determined, with copulation first observed on Day 25, egg shell protein formation observed on Day 28, and oviposition occurring on Day 30. In infections of S. haematobium, copulation first occurred on Day 29. Egg shell proteins were first formed on Day 45, and egg production occurred on Day 60. Examination of unisexual and bisexual infections showed that maturation of the vitellaria can be more easily assessed by autofluorescence of the protein globules than by the traditional diazonium salt stains. Autofluorescence of living worms with mature vitellaria allows subsequent examination by electron microscopy, and therefore permits evaluation at a subcellular level.     

Physical forces experienced by echinoid eggs in the oviduct during spawning: comparison of the geminate pair Echinometra vanbrunti and Echinometra lucunter

During spawning, eggs of echinoids are released from the gonad and traverse a narrow oviduct-gonopore complex before being released into the water surrounding the spawning female. As the eggs traverse the oviduct-gonopore complex, a velocity gradient develops within the fluid formed by the eggs. This velocity gradient imposes a shear stress on the eggs that ranges from a maximal value at the walls of the oviduct-gonopore complex and declines linearly to zero at the center of the complex. In addition to shear stress, the eggs of some echinoids also experience strain. Strain is imposed on the eggs in situations where the diameter of the egg is greater than the diameter of the oviduct-gonopore complex. Both shear stress and strain have the potential to damage echinoid eggs during spawning and are likely selective pressures acting on the physical properties of protective extracellular layers, which surround the eggs of these organisms. The amounts of shear stress and strain experienced by eggs of a geminate pair of echinoids, Echinometra vanbrunti and E. lucunter, are calculated. Calculations of shear stress based on the mean spawning rates and dimensions of the oviduct-gonopore complexes of specimens collected during this study ranged up to 30 Pa for E. vanbrunti and up to 17 Pa for E. lucunter. To obtain conservative estimates of shear stress, these calculations were repeated incorporating a spawning rate that was reduced by one order of magnitude below the mean rate measured for both species. These calculations yielded shear stresses that ranged up to 13 and 6 Pa for E. vanbrunti and E. lucunter, respectively. The diameter of the oviduct-gonopore complex of echinoids increases linearly with the diameter of the tests of the adults. Because the diameter of the oviduct-gonopore complex influences the amount of shear stress experienced by eggs of echinoids, shear stress calculations were repeated incorporating the full range of potential diameters of the oviduct-gonopore complexes from data in the literature. Using the mean spawning rates obtained from each species, the amount of shear stress experienced by eggs ranged up to 32 Pa for E. vanbrunti and up to 398 Pa for E. lucunter. When the mean spawning rates were reduced by one order of magnitude, the amount of shear stress experienced by E. vanbrunti eggs ranged up to 14 Pa and up to 140 Pa for the eggs of E. lucunter. The eggs of E. vanbrunti do not experience strain during spawning because the diameter of the its eggs is smaller than the diameter of its oviduct-gonopore complex at all stages of adult growth. In contrast, the diameter of the eggs of E. lucunter is larger than the diameter of the oviduct-gonopore complex at small adult sizes and the eggs of this species experience true strains ranging up to 1.2. These results indicate that there are substantial differences in the amounts of physical forces that the eggs of echinoids experience during spawning both within species at different stages of adult growth and between species. Different amounts of shear stress and strain experienced by eggs among echinoid species may select for differences in the mechanical properties of protective extracellular layers that surround them.     

Attaching NorA efflux pump inhibitors to methylene blue enhances antimicrobial photodynamic inactivation of Escherichia coli and Acinetobacter baumannii in vitro and in vivo

Resistance of bacteria to antibiotics is a public health concern worldwide due to the increasing failure of standard antibiotic therapies. Antimicrobial photodynamic inactivation (aPDI) is a promising non-antibiotic alternative for treating localized bacterial infections that uses non-toxic photosensitizers and harmless visible light to produce reactive oxygen species and kill microbes. Phenothiazinium photosensitizers like methylene blue (MB) and toluidine blue O are hydrophobic cations that are naturally expelled from bacterial cells by multidrug efflux pumps, which reduces their effectiveness. We recently reported the discovery of a NorA efflux pump inhibitor-methylene blue (EPI-MB) hybrid compound INF55-(Ac)en–MB that shows enhanced photodynamic inactivation of the Gram-positive bacterium methicillin-resistant Staphylococcus aureus (MRSA) relative to MB, both in vitro and in vivo. Here, we report the surprising observation that INF55-(Ac)en–MB and two related hybrids bearing the NorA efflux pump inhibitors INF55 and INF271 also show enhanced aPDI activity in vitro (relative to MB) against the Gram-negative bacteria Escherichia coli and Acinetobacter baumannii, despite neither species expressing the NorA pump. Two of the hybrids showed superior effects to MB in murine aPDI infection models. The findings motivate wider exploration of aPDI with EPI-MB hybrids against Gram-negative pathogens and more detailed studies into the molecular mechanisms underpinning their activity.     

Settlement decisions by the two-spotted spider mite Tetranychus urticae

In silk-spinning arthropods, silk can be used for web building, protection, and communication. Silk is an informative material about the presence of conspecifics. It can therefore inform on habitat suitability and hence assist in habitat choice. In this context, we investigated the influence of silk on microhabitat choice by the two-spotted spider mite, Tetranychus urticae. Three factors that could potentially influence habitat choice were manipulated: the strain, number, and the stage of mites. Our study showed that these factors all influence the choice of microhabitat. The tendency of whether to settle on a silk-covered area was influenced by the origin of mites (strain effect). Adult females showed a higher tendency to settle on an area covered with the silk laid by numerous congeners (number effect). Moreover, larvae seemed to be more responsive to the presence of silk than adults (stage effect). This suggests that individuals use silk as a social cue in selecting their microhabitat and that the spatial organization and group behaviour seem to be shaped by the individuals’ response to social cues, such as the amount of silk already present.     

Interconversion of trans, trans and cis, trans farnesol by enzymes from Andrographis

When trans, trans-farnesol [4,8,12-¹⁴C₃,1-³H₂] is isomerized to cis, trans-farnesol by soluble enzymes from Andrographis paniculata tissue cultures, 50% of the tritium label is lost. The same loss is observed when isomerization occurs in the opposite direction. This is in accordance with the proposed mechanism for isomerization via aldehydes.     

Protein secretion biotechnology in Gram-positive bacteria with special emphasis on Streptomyces lividans

Proteins secreted by Gram-positive bacteria are released into the culture medium with the obvious benefit that they usually retain their native conformation. This property makes these host cells potentially interesting for the production of recombinant proteins, as one can take full profit of established protocols for the purification of active proteins. Several state-of-the-art strategies to increase the yield of the secreted proteins will be discussed, using Streptomyces lividans as an example and compared with approaches used in some other host cells. It will be shown that approaches such as increasing expression and translation levels, choice of secretion pathway and modulation of proteins thereof, avoiding stress responses by changing expression levels of specific (stress) proteins, can be helpful to boost production yield. In addition, the potential of multi-omics approaches as a tool to understand the genetic background and metabolic fluxes in the host cell and to seek for new targets for strain and protein secretion improvement is discussed. It will be shown that S. lividans, along with other Gram-positive host cells, certainly plays a role as a production host for recombinant proteins in an economically viable way. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.     

Iridoid glucosides in Griselinia, Aralidium and Toricellia

From three of five investigated species of Griselinia a new iridoid glucoside, griselinoside, was isolated. It was found to be present also in foliage of Aralidium pinnatifidum and Toricellia angulata, accompanied in the former by aralidioside another novel iridoid glucoside. The structures and absolute configurations of the two iridoids were elucidated by NMR spectroscopy and chemical conversions. From G. littoralis and T. angulata the glucosides magnolioside and syringoside respectively were isolated. ¹³C NMR spectra are given for thirteen iridoid derivatives.     

Dinuclear ruthenium sawhorse-type complexes containing bridging ligands with ferrocenyl substituents in endo/endo, endo/exo and exo/exo orientations

The dinuclear ruthenium complexes Ru₂(CO)₄(OOCC₅H₄FeC₅H₅)₂L₂ (L = NC₅H₅: 1, L = PPh₃: 2) have been synthesized from Ru₃(CO)₁₂, ferrocene carboxylic acid and pyridine or triphenylphosphine, respectively. The single-crystal X-ray structure analysis reveals for 1 and 2 a Ru₂(CO)₄ sawhorse backbone with the two ferrocenyl substituents of the two carboxylato bridges being endo/exo with respect to each other in the solid state. With the new pyridine derivative NC₅H₄OOCC₅H₄FeC₅H₅ (4-ferrocenoyl pyridine) (3) as axial ligand, the complex Ru₂(CO)₄(OOCC₅H₄FeC₅H₅)₂(NC₅H₄OOCC₅H₄FeC₅H₅)₂ (4) was obtained, the single crystal X-ray structure analysis showing an exo/exo orientation of the two carboxylato bridges in the solid state. The endo/endo orientation is found in the solid-state structure of Ru₂(CO)₄(HNOCC₅H₄FeC₅H₅)₂(PPh₃)₂ (5), the two OCNH bridges being transoïd with respect to each other; this complex is accessible from Ru₃(CO)₁₂, ferrocenamide and triphenylphosphine.     

Genotypic alteration and competitive nodulation of Mesorhizobium muleiense against exotic chickpea rhizobia in alkaline soils

Mesorhizobium muleiense, Mesorhizobium mediterraneum and Mesorhizobium ciceri are chickpea (Cicer arietinum L.) rhizobia that share a high similarity of the symbiotic genes nodC and nifH, but they have different geographic distributions. M. muleiense has been isolated and found only in alkaline soils of Xinjiang, China, whereas the other two strains have been found in the Mediterranean and India. To investigate the species stability of M. muleiense during natural evolution and its capability of competitive nodulation against the other two exotic species, re-sampling of nodules in the field and competition experiments between the three species were conducted. The results showed that the predominant microsymbiont associated with chickpea grown in Xinjiang was still M. muleiense, but the predominant genotypes of M. muleiense had changed significantly during the four years since a previous survey. The data also showed that M. mediterraneum and M. ciceri were more competitive than the residential strain of M. muleiense CCBAU 83963^T in sterilized vermiculite or soils from Xinjiang. However, in non-sterilized soils, M. muleiense was the predominant nodule occupier. These results indicated that natural or adapting evolution of M. muleiense was occurring in fields subjected to changing environmental factors. In addition, the biogeography and symbiotic associations of rhizobia with their host legumes were also influenced by biological factors in the soil, such as indigenous rhizobia and other organisms.     

Nitrogen-containing non-steroidal secondary metabolites of Solanum, Cyphomandra, Lycianthes and Margaranthus

Of the 49 species of Solanum studied, cuscohygrine has been detected in 25, solamine and related amines in 17 and solamine-derived amides in 16. Five species of Cyphomandra examined all contained both amines and amides. From roots of Margaranthus solanaceus cuscohygrine has been isolated which probably occurs, too, in roots of Lycianthes rantonnettii. The distribution of these compounds throughout the taxa could be of chemotaxonomic value.     

Shoot/root assimilate allocation and nodulation ofVigna unguiculata seedlings as influenced by shoot light environment

Spectral balance of light received by southern pea [Vigna unguiculata (L.) Walp.] seedling shoots affected photoassimilate allocation among leaves, stems and roots. A higher ratio of far-red (FR) relative to red (R) light resulted in longer stems, higher shoot/root biomass ratio, less massive roots and fewer nodules. The same response pattern to FR/R ratio was obtained in a controlled environment with artificial light sources, or in sunlight where the FR/R ratio was modified by reflection from different colored soil surfaces or by FR reflected from competing plants. The importance of early shoot/root photoassimilate allocation and nodulation may differ according to soil nitrogen availability and moisture content.     

栓孔菌属漆酶高产菌株的初步筛选及其产酶条件的优化

利用显色反应对栓孔菌属(Trametes)进行了漆酶高产菌株的筛选,并对目标菌株的产酶条件进行了优化,在添加愈创木酚的固体培养基中,通过显色反应初步筛选出漆酶高产菌株东方栓孔菌Trametes orientalis Cui 6300;进一步通过单因子分析、正交试验和ABTS法确定了菌株Cui 6300的最适产酶条件:麦芽糖15 g/L,蛋白胨3 g/L,pH 4.8,Cu2+2.0 mmol/L,培养温度28°C,接种饼直径1.5 cm,此时酶活最高可达19.923 U/mL;同时探索了Cu2+浓度及添加时间对其菌丝生物量和漆酶活力的影响。研究表明,Cu2+最适添加浓度为2.0 mmol/L,添加时间为接种后第3天。