Localization and characterization of prolipoprotein diacylglyceryl transferase (Lgt) critical in bacterial lipoprotein biosynthesis

Lipid modification of proteins is an essential post-translational event that can be targeted for protein engineering and pharmaceutical applications. In this regard, the unique and ubiquitous bacterial N-terminal lipid modification (N-acyl S-diacylglyceryl modification of N-terminal cysteine) is particularly attractive. It is initiated by phosphatidylglycerol:prolipoprotein diacylglyceryl transferase (Lgt) and therefore its properties, which remain uninvestigated, largely define the specifics of the modification. A synthetic peptide-substrate (MKATKSAVGSTLAGCSSHHHHHH) with a short hydrophilic h-region, unlike that of the prototypical substrate used so far, demonstrated lack of enzyme's substrate preference based on hydrophobicity, perhaps accounting for a significant number of lipoproteins possessing hydrophilic signal peptides. Solubilization experiments revealed a peripheral and possibly reversible hydrophobic association of Lgt with the inner-membrane on the cytosolic side contradicting its deduced transmembrane topology. Except for heat stability, the soluble enzyme was indistinguishable from the membrane-bound enzyme in kinetic behaviour, indicating that the committed first step of bacterial lipid modification may be aqueous compatible. The direct, more accurate, precise and easier paper electrophoretic assay, designed anew, and Lgt's ready extraction with water or low ionic strength solutions from inverted vesicles could aid better understanding and exploitation of the enzyme and bacterial lipid modification.     

Recent advances in Pelargonium in vitro regeneration systems

Recent advances in the development of protocols for in vitro culture and genetic manipulation have provided new avenues for the development of novel varieties of Pelargonium and for use as model systems for investigating the factors controlling plant morphogenesis. Optimized techniques of meristem culture have supplemented the culture indexing methods in commercial greenhouse production resulting in availability of large-scale pathogen indexed planting material. Currently, technologies are available for the mass in vitro propagation of F1 hybrid Pelargonium through both organogenesis and somatic embryogenesis. The somatic embryogenesis model system has allowed researchers to identify critical factors controlling plant morphogenesis in vitro such as regulation of regeneration by growth regulators, choice of explant and characterization of induction and expression phases of morphogenesis in Pelargonium. Also, optimization of technologies for genetic transformation of Pelargonium opened up the possibilities for developing genotypes with novel characters, including resistance to some of the major diseases. Finally, the development of regeneration systems for Pelargonium spp. has facilitated conventional crop improvement programs, thereby providing a valuable resource to the horticultural industry.     

Protein degradation in aged nematodes (Turbatrix aceti).

The rates of degradation of total soluble proteins in the free-living nematode, $\text{Turbatrix aceti}$, have been estimated by following the loss of acid-insoluble insoluble radioactivity from protein during a nonradioactive chase period after initial labeling with [³⁵S]methionine. These proteins appear to lose label kinetically as a homogeneous class in age-synchronized nematode populations. However, proteins are degraded more slowly in senescent cultures than in young cultures. Protein degradation rates decline progressively during nematode aging. These findings suggest that the protein degradative system in T. aceti may become partially defective with advancing age which may result in the accumulation of aberrant protein molecules in senescent organisms.     

Synthesis of novel nitric oxide (NO)-releasing esters of timolol

A novel class of timolol derivatives with nitric oxide (NO)-donating moieties achieved chemical stability yet under physiologically relevant conditions released timolol and NO. Hindered esters A were designed and synthesized, whose ‘triggered’ release relied on enzymatic hydrolysis of the nitrate ester in A to B, that in turn cyclized to liberate timolol.     

Endophytic bacterial flora in the stem tissue of a tropical maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) genotype: isolation,identification and enumeration

The genotypic diversity of indigenous bacterial endophytes within stem of tropical maize (Zea mays L.) was determined in field and greenhouse experiments. Strains were isolated from stem tissues of a tropical maize cultivar (PEHM-1) by trituration and surface disinfestation and their population dynamics was determined. Endophytes were found in most of the growing season at populations ranging from 1.36–6.12 × 10⁵ colony-forming units per gram fresh weight (c.f.u./gm fw) of stem. Analysis of these bacterial endophytes using Gas Chromatography—Fatty Acid Methyl Ester (GC-FAME) led to the identification of Bacillus pumilus, B. subtilis, Pseudomonas aeruginosa and P. fluorescens as the relatively more predominant group of bacterial species residing in maize stem. When the maize seedlings grown in a greenhouse were inoculated with these four isolates individually, their population densities decreased (1.6–3.1 × 10⁵ c.f.u./gm fw of stem) as compared to the field-grown maize (1.8–3.8 × 10⁵ c.f.u./gm fw of stem). The highest persistence, however, was recovered in the case of B. subtilis with a population density of 3.1 × 10⁵ c.f.u./gm fw of stem tissue on 28 days after emergence (DAE). This is the first report on population dynamics of bacterial endophytes from tropical maize and the results establish that symptomless populations of bacteria exist in the maize stem.     

Redistribution of nitrogen in an ecosystem due to long-term fertilization and continuous cropping

Summary When a leguminous crop like cowpea was included in a crop rotation of Ganga 5 maize, CO 7 ragi and CO 2 cowpea, the total nitrogen content in the soil was considerably increased even in the unfertilized plots. The leguminous crop fixed atmospheric nitrogen at the rate of 205 kg N/hectare/year. Potassium did not influence the status whereas phosphorus, over a background of N, improved it. Considerable quantity of N fixed was observed to have been redistributed in the soil which depended on the fertilization pattern.     

Liver peptide stabilizing factor protects phosphofructokinase against inactivation by fructose-1,6-bisphosphatase.

Rabbit liver fructose-1,6-bisphosphatase (FDPase) can reversibly inactivate both rabbit muscle and rat liver phosphofructokinases (PFK) under appropriate conditions. The peptide factor which stabilizes rat liver PFK-L₂ against thermal inactivation has now been found to protect both PFKs from inactivation by FDPase. Assay at high ATP (ca. 3 mM) is necessary to demonstrate these reversible changes. In addition, the activation of FDPase by liver cytosol, by oleate plus cytosol, or by oleate plus muscle PFK is lowere about 50% in the presence of peptide factor. These observations suggest an active participation of the peptide factor in regulation of liver glycolysis and gluconeogenesis.     

Nitrogen fixation ability explains leaf chemistry and arbuscular mycorrhizal responses to fertilization

Atmospheric nitrogen (N) and phosphorus (P) deposition rates are predicted to drastically increase in the coming decades. The ecosystem level consequences of these increases will depend on how plant tissue nutrient concentrations, stoichiometry and investment in nutrient uptake mechanisms such as arbuscular mycorrhizal fungi (AMF) change in response to increased nutrient availability, and how responses differ between plant functional types. Using a factorial nutrient addition experiment with seedlings of multiple N-fixing and non-N-fixing tree species, we examined whether leaf chemistry and AMF responses differ between these dominant woody plant functional groups of tropical savanna and dry forest ecosystems. We found that N-fixers have remarkably stable foliar chemistry that stays constant with external input of nutrients. Non-N-fixers responded to N and N + P addition by increasing both concentrations and total amounts of foliar N, but showed a corresponding decrease in P concentrations while total amounts of foliar P stayed constant, suggesting a ‘dilution’ of tissue P with increased N availability. Non-N-fixers also showed an increase in N:P ratios with N and N + P addition, probably driven by both an increase in N and a decrease in P concentrations. AMF colonization decreased with N + P addition in non-N-fixers and increased with N and N + P addition in N-fixers, suggesting differences in their nutrient acquisition roles in the two plant functional groups. Our results suggest that N-fixers and non-N-fixers can differ significantly in their responses to N and P deposition, with potential consequences for future nutrient and carbon cycling in savanna and dry forest ecosystems.     

Interfacial Effects of Tin Oxide Atomic Layer Deposition in Metal Halide Perovskite Photovoltaics

Metal halide perovskites offer a wide and tunable bandgap, making them promising candidates for top‐cell absorbers in tandem photovoltaics. In this work, the authors aim to understand the atomic layer deposition (ALD) precursor–perovskite interactions of the tin oxide ALD system and the role of organic fullerenes at the perovskite–tin oxide interface while establishing a framework for developing alternative perovskite‐compatible ALD processes in the future. It is shown, in the case of tin oxide ALD growth with tetrakis(dimethylamino)tin(IV) and water on FA_0.83Cs_0.17Pb(I_0.83Br_0.17)₃ perovskite, that perovskite stability is most sensitive to metal–organic exposure at elevated temperatures with an onset near 110 °C, resulting in removal of the formamidinium cation. Transitioning from ALD to pulsed‐chemical vapor deposition tin oxide growth can minimize the degradation effects. Investigation of fullerenes at the perovskite interface shows that thin fullerene layers offer minor improvements to perovskite stability under ALD conditions, but significant enhancement in carrier extraction. Fullerene materials are undesirable due to fabrication cost and poor mechanical stability. Compositional tuning of the perovskite material can improve the fullerene‐free device performance. This method is demonstrated with a bromine‐rich perovskite phase to enable an 8.2% efficient perovskite device with all‐inorganic extraction layers.