Travellers' malaria - 'one shoe does not fit all'

Travellers' malaria is an exciting topic. It is a field in flux with evolving options for chemoprophylaxis, self-diagnosis, self-treatment, risk/strategy analyses and surveillance. Ideologies vary and experts differ but debate is needed and can bring change. The launch of a new thematic series in the Malaria Journal -- " Travellers' malaria " -- creates an ideal forum to bring together research papers, reviews, opinion papers and commentaries, and will hopefully stimulate debate.     

Extracellular expression, purification, and characterization of a winter flounder antifreeze polypeptide from Escherichia coli

HPLC6 is the major component of liver-type antifreeze polypeptides (AFPs) from the winter flounder, Pleuronectes americanus. To facilitate mutagenesis studies of this protein, a gene encoding the 37-amino acid mature polypeptide was chemically synthesized and cloned into the Tac cassette immediately after the bacterial ompA leader sequence for direct excretion of the AFP into the culture medium. Escherichia coli transformant with the construct placIQpar8AF was cultured in M9 medium. The recombinant AFP (rAFP) was detected by a competitive enzyme-linked immunosorbent assay (ELISA). After IPTG induction, a biologically active rAFP was expressed. The majority of the rAFP was excreted into the culture medium with only trace amounts trapped in the periplasmic space and cytoplasm. After 18 h of induction, the accumulated rAFP in the culture medium amounted to about 16 mg/L. The excreted AFP was purified from the culture medium by a single-step reverse-phase HPLC. Mass spectrometric and amino acid composition analyses confirmed the identity of the purified product. The rAFP, which lacked amidation at the C-terminal, was about 70% active when compared to the amidated wild-type protein, thus confirming the importance of C-terminal cap structure in protein stability and function.     

Molecular Evidence for a Deep Clade of Dunnarts (Marsupialia: Dasyuridae: Sminthopsis)

Sminthopsis is the most speciose genus of living dasyurid marsupials and, along with its close relatives Antechinomys and Ningaui, constitutes the clade Sminthopsini. Phylogenetic relationships among the 23 species in this clade have been the subject of much morphological and molecular investigation, including a recent integration of penis morphology (in Sminthopsis) with molecular systematics. Several phylogenetic issues remain open, however, including the monophyly of Sminthopsis and branching order among early sminthopsin lineages. In this study, we revisit sminthopsin systematics with an expanded molecular data set, including new DNA sequences from mitochondrial (valine transfer-RNA and 16S ribosomal RNA) and nuclear (interphotoreceptor retinoid binding protein and beta-fibrinogen) loci, along with previously published sequences of cytochrome b, 12S ribosomal RNA, control region, and protamine P1. Our results again fail to establish the monophyly of Sminthopsis, but do provide a clearer resolution of early sminthopsin branching. Specifically, our phylogeny suggests three major groups of Sminthopsis species: S. longicaudata (perhaps the sister of Antechinomys); the Macroura species group of previous authors (S. crassicaudata, S. macroura, S. virginiae, S. douglasi, and S. bindi); and the remaining 13 species allied with the Murina species group. Our results depart from previous molecular findings by reuniting S. ooldea with the Murina group, while resolving S. psammophila as sister to the hairy-footed dunnarts (S. hirtipes and S. youngsoni). We suggest that this conflict traces to anomalous phylogenetic signal in previously published cytochrome b sequences. Penis morphology maps reasonably well onto our phylogeny, requiring parallel origination of only one of the ten morphotypes described for Sminthopsis.     

Genome-inferred spatio-temporal resolution of an uncultivated Roizmanbacterium reveals its ecological preferences in groundwater

Subsurface ecosystems like groundwater harbour diverse microbial communities, including small-sized, putatively symbiotic organisms of the Candidate Phyla Radiation, yet little is known about their ecological preferences and potential microbial partners. Here, we investigated a member of the superphylum Microgenomates (Cand. Roizmanbacterium ADI133) from oligotrophic groundwater using mini-metagenomics and monitored its spatio-temporal distribution using 16S rRNA gene analyses. A Roizmanbacteria-specific quantitative PCR assay allowed us to track its abundance over the course of 1 year within eight groundwater wells along a 5.4 km hillslope transect, where Roizmanbacteria reached maximum relative abundances of 2.3%. In-depth genomic analyses suggested that Cand. Roizmanbacterium ADI133 is a lactic acid fermenter, potentially able to utilize a range of complex carbon substrates, including cellulose. We hypothesize that it attaches to host cells using a trimeric autotransporter adhesin and inhibits their cell wall biosynthesis using a toxin–antitoxin system. Network analyses based on correlating Cand. Roizmanbacterium ADI133 abundances with amplicon sequencing-derived microbial community profiles suggested one potential host organism, classified as a member of the class Thermodesulfovibrionia (Nitrospirae). By providing lactate as an electron donor Cand. Roizmanbacterium ADI133 potentially mediates the transfer of carbon to other microorganisms and thereby is an important connector in the microbial community.     

ApoC-III content of apoB-containing lipoproteins is associated with binding to the vascular proteoglycan biglycan

Retention of apolipoprotein (apo)B and apoE-containing lipoproteins by extracellular vascular proteoglycans is critical in atherogenesis. Moreover, high circulating apoC-III levels are associated with increased atherosclerosis risk. To test whether apoC-III content of apoB-containing lipoproteins affects their ability to bind to the vascular proteoglycan biglycan, we evaluated the impact of apoC-III on the interaction of [(35)S]SO(4)-biglycan derived from cultured arterial smooth muscle cells with lipoproteins obtained from individuals across a spectrum of lipid concentrations. The extent of biglycan binding correlated positively with apoC-III levels within VLDL (r = 0.78, P < 0.01), IDL (r = 0.67, P < 0.01), and LDL (r = 0.52, P < 0.05). Moreover, the biglycan binding of VLDL, IDL, and LDL was reduced after depletion of apoC-III-containing lipoprotein particles in plasma by anti-apoC-III immunoaffinity chromatography. Since apoC-III does not bind biglycan directly, enhanced biglycan binding may result from a conformational change associated with increased apo C-III content by which apoB and/or apoE become more accessible to proteoglycans. This may be an intrinsic property of lipoproteins, since exogenous apoC-III enrichment of LDL and VLDL did not increase binding. ApoC-III content may thus be a marker for lipoproteins characterized as having an increased ability to bind proteoglycans.