β-Ketoacyl-ACP synthase I/II fromPlasmodium falciparum(PfFabB/F)-Is it B or F?

The nutrient games - Plasmodium metabolism during hepatic development

Malaria is a febrile illness caused by species of the protozoan parasite Plasmodium and is characterized by recursive infections of erythrocytes, leading to clinical symptoms and pathology. In mammals, Plasmodium parasites undergo a compulsory intrahepatic development stage before infecting erythrocytes. Liver-stage parasites have a metabolic configuration to facilitate the replication of several thousand daughter parasites. Their metabolism is of interest to identify cellular pathways essential for liver infection, to kill the parasite before onset of the disease. In this review, we summarize the current knowledge on nutrient acquisition and biosynthesis by liver-stage parasites mostly generated in murine malaria models, gaps in knowledge, and challenges to create a holistic view of the development and deficiencies in this field.

Improving the viability of powdered Lactobacillus fermentum Lf01 with complex lyoprotectants by maintaining cell membrane integrity and regulating related genes

In this study, Lactobacillus fermentum Lf01, which was screened out in the early stage of the experiment, had better fermentation performance as the research objectives, and was prepared into powder by vacuum freeze-drying technology. We used response surface methodology to optimize the composition of the mixture used to protect powdered L. fermentum. Our data demonstrated that 10% skim milk, 12% sucrose, 0.767% tyrosine, and 2.033% sorbitol ensured the highest survival rate (92.7%) of L. fermentum. We have initially explored the potential mechanism of the complex protectants through the protection effect under the electron microscope, and the analysis methods of Fourier transform infrared spectroscopy and transcriptomics. The complex protectants could effectively maintain the permeability barrier and structural integrity of cell membrane and avoid the leakage of cell contents. Transcriptomic data have also indicated that the protective effect of the complex protectants on bacteria during freeze-drying was most likely achieved through the regulation of related genes. We identified 240 differential genes in the treatment group, including 231 up-regulated genes and 9 down-regulated genes. Gene ontology (GO) and Kyoto encyclopaedia of genes and genomes (KEGG) analyses of differential expression genes (DEGs) indicated that genes involved in amino acid metabolism, carbohydrate metabolism, membrane transport, fatty acid biosynthesis and cell growth were significantly up-regulated. These new results provided novel insights into the potential mechanism of lyoprotectants at the cellular level, morphological level, and gene level of the bacteria. PRACTICAL APPLICATIONS: In our study, a strain of Lactobacillus fermentum Lf01 with good fermentation performance was selected to be prepared into powder by freeze-drying technique. Bacterial cells were unavoidably damaged during the freeze-drying process. As a result, we investigated the protective effects on L. fermentum of ten distinct freeze-dried protectants and their mixtures. We were also attempting to explain the mechanism of action of the complex protectants at the cellular level, morphological level, and gene level of the bacteria. This presents very important theoretical and practical significance for the preservation of strains and the production of commercial direct-investment starter.

Relict plastidic metabolic process as a potential therapeutic target

The alignment of the evolutionary history of parasites with that of plants provides a different panorama in the drug development process. The housing of different metabolic processes, essential for parasite survival, adds to the indispensability of the apicoplast. The different pathways responsible for fueling the apicoplast and parasite offer a myriad of proteins responsible for the apicoplast function. The studies emphasizing the target-based approaches might help in the discovery of antimalarials. The different putative drug targets and their roles are highlighted. In addition, the origin of the apicoplast and metabolic processes are reviewed and the different drugs acting upon the enzymes of the apicoplast are discussed.

Assessing the adequacy of attenuation of genetically modified malaria parasite vaccine candidates

The critical first step in the clinical development of a malaria vaccine, based on live-attenuated Plasmodium falciparum sporozoites, is the guarantee of complete arrest in the liver. We report on an approach for assessing adequacy of attenuation of genetically attenuated sporozoites in vivo using the Plasmodium berghei model of malaria and P. falciparum sporozoites cultured in primary human hepatocytes. We show that two genetically attenuated sporozoite vaccine candidates, Δp52+p36 and Δfabb/f, are not adequately attenuated. Sporozoites infection of mice with both P. berghei candidates can result in blood infections. We also provide evidence that P. falciparum sporozoites of the leading vaccine candidate that is similarly attenuated through the deletion of the genes encoding the proteins P52 and P36, can develop into replicating liver stages. Therefore, we propose a minimal set of screening criteria to assess adequacy of sporozoite attenuation necessary before advancing into further clinical development and studies in humans.

DETECT--a density estimation tool for enzyme classification and its application to Plasmodium falciparum

MOTIVATION

A major challenge in genomics is the accurate annotation of component genes. Enzymes are typically predicted using homology-based search methods, where the membership of a protein to an enzyme family is based on single-sequence comparisons. As such, these methods are often error-prone and lack useful measures of reliability for the prediction.

RESULTS

Here, we present DETECT, a probabilistic method for enzyme prediction that accounts for the sequence diversity across enzyme families. By comparing the global alignment scores of an unknown protein to those of all known enzymes, an integrated likelihood score can be readily calculated, ranking the reaction classes relevant for that protein. Comparisons to BLAST reveal significant improvements in enzyme annotation accuracy. Applied to Plasmodium falciparum, we identify potential annotation errors and predict novel enzymes of therapeutic interest.

AVAILABILITY

A standalone application is available from the website: http://www.compsysbio.org/projects/DETECT/