Microbial protein from leguminous and non-leguminous substrates

The biodegradation of leguminous and non-leguminous organic materials by Pleurotus sajor-caju and P. ostreatus was studied. Comparisons were made between mushroom yield on both types of substrates. The conversion percentage from dry substrate to fresh mushroom (biological efficiency) was determined. Mushrooms were analyzed for their protein content, carbohydrates, percentages of ash, fat content and crude fibre. The energy value of fruit bodies was computed. The yield obtained from leguminous substrates was significantly high as compared to that yield which was obtained from non-leguminous substrates. The lowest yield of P. sajor caju (10 g ± 0.3 g) and P. ostreatus (6.5 g ± 1.2 g) was obtained using the Bougainuillea substrate and the highest one (519 g ± 16 g, P. sajor-caju and 488 g ± 18 g, P. ostreatus) using nitrogen-fixing leguminous Leucaena leucocepholea. The nitrogen content in fruit bodies was found to be higher with leguminous substrate than with non-leguminous ones.     

Nitrogen-fixing bacteria associated with leguminous and non-leguminous plants

Nitrogen is generally considered one of the major limiting nutrients in plant growth. The biological process responsible for reduction of molecular nitrogen into ammonia is referred to as nitrogen fixation. A wide diversity of nitrogen-fixing bacterial species belonging to most phyla of the Bacteria domain have the capacity to colonize the rhizosphere and to interact with plants. Leguminous and actinorhizal plants can obtain their nitrogen by association with rhizobia or Frankia via differentiation on their respective host plants of a specialized organ, the root nodule. Other symbiotic associations involve heterocystous cyanobacteria, while increasing numbers of nitrogen-fixing species have been identified as colonizing the root surface and, in some cases, the root interior of a variety of cereal crops and pasture grasses. Basic and advanced aspects of these associations are covered in this review.     

Nitrogenase activity in rhizobium associated with leguminous and non-leguminous tissue cultures

Nitrogenase activity was observed in root-, stem- and leaf-tissue cultures of three genetic lines of Trifolium pratense infected with Rhizobium trifolii Rothamsted Strain 5, Stylosanthes gracilis with Rhizobium sp. Strain CB1552 and root-tissue cultures of carrot with Strains CB1552 and NGR99. Rhizobium (CB1552) previously associated with Stylosanthes tissues continued to show nitrogenase activity for 5 days after separation from the callus. Infected Trifolium callus differentiated to produce roots in 8 weeks on a medium free from NO₃⁻, 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin, whereas the uninfected callus remained undifferentiated.     

Patterns in leaf traits of leguminous and non-leguminous dominant trees along a rainfall gradient in Ghana

Aims Both dominance distribution of species and the composition of the dominant species determine the distribution of traits within community. Leaf carbon (C) and nitrogen (N) isotopic composition are important leaf traits, and such traits of dominant species are associated with ecosystem C, water and N cycling. Very little is known how dominant species with distinct traits (e.g. N-fixing leguminous and non-leguminous trees) mediate resource utilization of the ecosystems in stressful environment.Methods Leaves of 81 dominant leguminous and non-leguminous trees were collected in forest (moist semi-deciduous and dry semi-deciduous ecosystems) and savanna (costal savanna, Guinean savanna and west Sudanian savanna ecosystems) areas and the transitional zone (between the forest and the savanna) along the transect from the south to the north of Ghana. We measured leaf traits, i.e. leaf δ 13 C, leaf δ 15 N, leaf water content, leaf mass per area (LMA) and C and N concentration. Correlation analyses were used to examine trait–trait relationships, and relationships of leaf traits with temperature and precipitation. We used analysis of covariance to test the differences in slopes of the linear regressions between legumes and non-legumes.Important findings Leaf δ 13 C, δ 15 N, leaf water content and LMA did not differ between leguminous and non-leguminous trees. Leaf N concentration and C:N ratio differed between the two groups. Moreover, leaf traits varied significantly among the six ecosystems. δ 13 C values were negatively correlated with annual precipitation and positively correlated with mean annual temperature. In contrast, leaf δ 15 N of non-leguminous trees were positively correlated with annual precipitation and negatively correlated with mean annual temperature. For leguminous trees, such correlations were not significant. We also found significant coordination between leaf traits. However, the slopes of the linear relationships were significantly different between leguminous and non-leguminous trees. Our results indicate that shifts in dominant trees with distinct water-use efficiency were corresponded to the rainfall gradient. Moreover, leguminous trees, those characterized with relative high water-use efficiency in the low rainfall ecosystems, were also corresponded to the relative high N use efficiency. The high proportion of leguminous trees in the savannas is crucial to mitigate nutrient stress.     

Effects of nitrogen addition on litter decomposition, soil microbial biomass, and enzyme activities between leguminous and non-leguminous forests

Anthropogenic nitrogen (N) deposition is an expanding problem that affects the functioning and composition of forest ecosystems, particularly the decomposition of forest litters. Legumes play an important role in the nitrogen cycle of forest ecosystems. Two litter types were chosen from Zijin Mountain in China: Robinia pseudoacacia leaves from a leguminous forest (LF) and Liquidambar formosana leaves from a non-leguminous forest (NF). The litter samples were mixed into original forest soils and incubated in microcosms. Then, they were treated by five forms of N addition: NH₄ ⁺, NO₃ ^?, urea, glycine, and a mixture of all four. During a 6-month incubation period, litter mass losses, soil microbial biomass, soil pH, and enzyme activities were investigated. Results showed that mixed N and NO₃ ^?-N addition significantly accelerated the litter decomposition rates of LF leaves, while mixed N, glycine-N, and urea-N addition significantly accelerated the litter decomposition rates of NF leaves. Litter decomposition rates and soil enzyme activities under mixed N addition were higher than those under single form of N additions in the two forest types. Nitrogen addition had no significant effects on soil pH and soil microbial biomass. The results indicate that nitrogen addition may alter microbial allocation to extracellular enzyme production without affecting soil microbial biomass, and then affected litter decomposition process. The results further reveal that mixed N is a more important factor in controlling litter decomposition process than single form of N, and may seriously affect soil N cycle and the release of carbon stored belowground.     

塔克拉玛干沙漠南缘豆科与非豆科植物的氮分配

在豆科与非豆科植物光合特性的研究中发现,非豆科植物具有更高的光合速率,与其低的叶氮含量相矛盾。在沙漠中氮素是限制植物生长的关键因子之一,考虑到豆科植物的生物固氮作用和叶氮大部分分配于光合系统,我们假设:(1)非豆科植物具有更低的叶氮含量;(2)分配更少的叶氮于光合系统;(3)具有更高的最大净光合速率(Pmax)和光合氮素利用效率(PNUE)。为了验证这些假设,以塔克拉玛干沙漠南缘的豆科植物骆驼刺(Alhagi sparsifolia)和非豆科植物柽柳(Tamarix ramosissima)、花花柴(Karelinia caspica)为研究对象,比较了它们的叶氮含量、氮分配、Pmax和PNUE等。结果表明:(1)非豆科植物比豆科植物确实有更低的叶氮含量,且差异达到显著水平;(2)非豆科植物分配更少的叶氮于光合系统,但在光合系统内部具有更高效的氮分配机制;(3)非豆科植物具有更高的Pmax和PNUE。在光合系统内部,非豆科植物分配更多的叶氮于羧化系统,而豆科植物分配更多的叶氮于捕光系统。对于非豆科植物而言,其更高的Pmax、PNUE、水分利用效率和表观量子产量,取决于将更多的叶氮投入到羧化和电子传递系统中。这些生理优势决定了塔克拉玛干沙漠南缘非豆科植物高效的资源捕捉和利用能力。     

Apoptosis-inducing antifungal peptides and proteins

Despite the availability of various classes of antimycotics, the treatment of patients with systemic fungal infections is challenging. Therefore the development of new antifungals is urgently required. Promising new antifungal candidates are antimicrobial peptides. In the present review, we provide an overview of antifungal peptides isolated from plants, insects, amphibians and mammals that induce apoptosis. Their antifungal spectrum, mode of action and toxicity are discussed in more detail.     

Plant-derived antifungal proteins and peptides

Plants produce potent constitutive and induced antifungal compounds to complement the structural barriers to microbial infection. Approximately 250,000-500,000 plant species exist, but only a few of these have been investigated for antimicrobial activity. Nevertheless, a wide spectrum of compound classes have been purified and found to have antifungal properties. The commercial potential of effective plant-produced antifungal compounds remains largely unexplored. This review article presents examples of these compounds and discusses their properties.     

Antifungal peptides: Origin, activity, and therapeutic potential

Antifungal peptides have been identified in a wide range of life forms which include plants, mammals, and microorganisms. Their structures are as varied as their antifungal properties. Semisynthetic and fully synthetic analogs have been developed from a few of these natural peptides that are superior to the parent compound. A few of these peptides hold promise in combating fungal infections and have entered clinical trials.     

Gas-phase hydrolysis of proteins and peptides

A simplified gas-phase hydrolysis procedure for proteins and peptides is described. The apparatus consists of a glass vacuum desiccator, a ceramic plate, and a Teflon ring. The method was shown to give reproducible compositions for hydrolysis of human serum albumin and microanalysis of α-melanocyte stimulating hormone including the quantitation of as little as one residue of tryptophan. It minimizes sample handling and allows for the simultaneous hydrolysis of a large number of samples.     

Antifungal properties of Canavalia ensiformis urease and derived peptides

Ureases (EC 3.5.1.5) are metalloenzymes that hydrolyze urea into ammonia and CO₂. These proteins have insecticidal and fungicidal effects not related to their enzymatic activity. The insecticidal activity of urease is mostly dependent on the release of internal peptides after hydrolysis by insect digestive cathepsins. Jaburetox is a recombinant version of one of these peptides, expressed in Escherichia coli. The antifungal activity of ureases in filamentous fungi occurs at submicromolar doses, with damage to the cell membranes. Here we evaluated the toxic effect of Canavalia ensiformis urease (JBU) on different yeast species and carried out studies aiming to identify antifungal domain(s) of JBU. Data showed that toxicity of JBU varied according to the genus and species of yeasts, causing inhibition of proliferation, induction of morphological alterations with formation of pseudohyphae, changes in the transport of H⁺ and carbohydrate metabolism, and permeabilization of membranes, which eventually lead to cell death. Hydrolysis of JBU with papain resulted in fungitoxic peptides (∼10 kDa), which analyzed by mass spectrometry, revealed the presence of a fragment containing the N-terminal sequence of the entomotoxic peptide Jaburetox. Tests with Jaburetox on yeasts and filamentous fungi indicated a fungitoxic activity similar to ureases. Plant ureases, such as JBU, and its derived peptides, may represent a new alternative to control medically important mycoses as well as phytopathogenic fungi, especially considering their potent activity in the range of 10⁻⁶–10⁻⁷ M.     

NMR spectroscopy of peptides and proteins

High resolution nuclear magnetic resonance (NMR) spectroscopy is the only method available for determining the three-dimensional structures of peptides and proteins in solution at atomic resolution. This article deals with a range of practical considerations associated with such studies, including sample preparation, instrumental setup, one- and two-dimensional NMR methods, interpretation of spectral data, and structure calculations.