Peptide arrays: from macro to micro

Over the past decade of proteome research peptide arrays have become a widespread and powerful tool to study molecular recognition events and to identify biologically active peptides. A variety of applications such as epitope mapping, characterisation of protein-protein interactions, enzyme-substrate or inhibitor interactions, and many more, have been published. Today's technologies for array production, inspired by DNA chips, have recently turned to the miniaturisation of peptide arrays. These advances open up an expanding spectrum of applications and the information obtained will be well-suited to developing substrates and inhibitors for diagnostic and therapeutic purposes.     

Coupled and uncoupled proton movement by amino acid transport system N.

The system N transporter SN1 has been proposed to mediate the efflux of glutamine from cells required to sustain the urea cycle and the glutamine-glutamate cycle that regenerates glutamate and gamma-aminobutyric acid (GABA) for synaptic release. We now show that SN1 also mediates an ionic conductance activated by glutamine, and this conductance is selective for H(+). Although SN1 couples amino acid uptake to H(+) exchange, the glutamine-gated H(+) conductance is not stoichiometrically coupled to transport. Protons thus permeate SN1 both coupled to and uncoupled from amino acid flux, providing novel mechanisms to regulate the transfer of glutamine between cells.     

Tolerance of Listeria monocytogenes to Quaternary Ammonium Sanitizers Is Mediated by a Novel Efflux Pump Encoded by emrE

A novel genomic island (LGI1) was discovered in Listeria monocytogenes isolates responsible for the deadliest listeriosis outbreak in Canada, in 2008. To investigate the functional role of LGI1, the outbreak strain 08-5578 was exposed to food chain-relevant stresses, and the expression of 16 LGI1 genes was measured. LGI1 genes with putative efflux (L. monocytogenes emrE [emrE_Lm]), regulatory (lmo1851), and adhesion (sel1) functions were deleted, and the mutants were exposed to acid (HCl), cold (4°C), salt (10 to 20% NaCl), and quaternary ammonium-based sanitizers (QACs). Deletion of lmo1851 had no effect on the L. monocytogenes stress response, and deletion of sel1 did not influence Caco-2 and HeLa cell adherence/invasion, whereas deletion of emrE resulted in increased susceptibility to QACs (P < 0.05) but had no effect on the MICs of gentamicin, chloramphenicol, ciprofloxacin, erythromycin, tetracycline, acriflavine, and triclosan. In the presence of the QAC benzalkonium chloride (BAC; 5 μg/ml), 14/16 LGI1 genes were induced, and lmo1861 (putative repressor gene) was constitutively expressed at 4°C, 37°C, and 52°C and in the presence of UV exposure (0 to 30 min). Following 1 h of exposure to BAC (10 μg/ml), upregulation of emrE (49.6-fold), lmo1851 (2.3-fold), lmo1861 (82.4-fold), and sigB (4.1-fold) occurred. Reserpine visibly suppressed the growth of the ΔemrE_Lm strain, indicating that QAC tolerance is due at least partially to efflux activity. These data suggest that a minimal function of LGI1 is to increase the tolerance of L. monocytogenes to QACs via emrE_Lm. Since QACs are commonly used in the food industry, there is a concern that L. monocytogenes strains possessing emrE will have an increased ability to survive this stress and thus to persist in food processing environments.     

Unexpected diversity and a new species of Epizoanthus (Anthozoa,Hexacorallia) attached to eunicid worm tubes from the Pacific Ocean

Epizoanthus species are generally found in association with other marine invertebrates such as hermit crabs and gastropods. Although Epizoanthus spp. are relatively common, there is limited information about their diversity and ecology due to their habitats or hosts, often being below the depths of SCUBA diving (>~50 m). In particular, the Epizoanthus fauna of the Indo-Pacific Ocean remains poorly understood. In this study, the diversity of Epizoanthus species associated with eunicid worm tubes from shallow waters in the Pacific Ocean we investigated using molecular analyses (mitochondrial cytochrome oxidase subunit 1 = COI, mitochondrial 16S ribosomal DNA = mt 16S-rDNA, nuclear internal transcribed spacer region of ribosomal DNA = ITS-rDNA) combined with morphological and ecological data. The combined data set leads us to describe two new species; Epizoanthus inazuma sp. n. and Epizoanthus beriber sp. n. Both new species are found in low-light environments: Epizoanthus inazuma sp. n. on mesophotic coral reef slopes and reef floors, or on the sides of overhangs; Epizoanthus beriber sp. n. has only been found in caves. Morphological characteristics of these two new species are very similar to Epizoanthus illoricatus Tischbierek, 1930 but the two new species are genetically distinct. Mesentery numbers and coloration of polyps may be useful diagnostic characteristics among eunicid-associated Epizoanthus species. These results demonstrate that there is high potential for other potentially undescribed zoantharian species, particularly in underwater cave habitats.     

Evidence for subdivision within the M molecular form of Anopheles gambiae

The principal vector of malaria in sub-Saharan Africa, Anopheles gambiae is subdivided into two molecular forms M and S. Additionally, several chromosomal forms, characterized by the presence of various inversion polymorphisms, have been described. The molecular forms M and S each contain several chromosomal forms, including the Savanna, Mopti and Forest forms. The M and S molecular forms are now considered to be the reproductive units within A. gambiae and it has recently been argued that a low recombination rate in the centromeric region of the X chromosome has facilitated isolation between these forms. The status of the chromosomal forms remains unclear however. Therefore, we studied genetic differentiation between Savanna S, Forest S, Forest M and Mopti M populations using microsatellites. Genetic differentiation between Savanna S and Forest S populations is very low (F(ST) = 0.0053 +/- 0.0049), even across large distances. In comparison, the Mopti M and Forest M populations show a relatively high degree of genetic differentiation (F(ST) = 0.0406 +/- 0.0054) indicating that the M molecular form may not be a single entity, but could be subdivided into at least two distinct chromosomal forms. Previously it was proposed that inversions have played a role in the origin of species within the A. gambiae complex. We argue that a possible subdivision within the M molecular form could be understood through this process, with the acquisition of inversions leading to the expansion of the M molecular form into new habitat, dividing it into two distinct chromosomal forms.