The survival of three strains of Arcobacter butzleri in the presence of lemon, orange and bergamot essential oils and their components in vitro and on food

AIMS: To test the effect of oils and vapours of lemon, sweet orange and bergamot and their components against three Arcobacter butzleri strains. METHODS AND RESULTS: The disc diffusion method was used to screen the oils and vapours against three strains of A. butzleri. In vitro bergamot was the most inhibitory essential oil (EO) and both citral and linalool were effective. On cabbage leaf, the water isolate was the least susceptible to bergamot EO, citral and linalool (1-2 log reduction), with the chicken isolate being the most susceptible (6-8 log reduction). However, the latter appeared not to be susceptible to vapours over 24 h although type strain and water isolate populations reduced by 8 logs. On chicken skin, the effectiveness of the oils was reduced compared with that on cabbage leaf. CONCLUSIONS: Bergamot was the most effective of the oils tested and linalool the most effective component. All strains tested were less susceptible in food systems than in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: Arcobacter isolates vary in their response to EO suggesting that the results of type strain studies should be interpreted with caution. Bergamot EO has the potential for the inhibition of this 'emerging' pathogen.     

TAXONOMY OF THE LENORMANDIA - LENORMANDIOPSIS COMPLEX (RHODOMELACEAE, RHODOPHYTA)

The genus Lenormandia is composed of nine species from Australia and New Zealand. Some of the these are well known, but others are rare, obscure and ill-defined. We have examined material of all described species and found that they fall into two discrete groups that differ in apex morphology and position of reproductive structures. Plants of the first group, containing the type species L. spectabilis , have a cleft apex and reproductive structures produced directly on the blade surface, whereas those of the second group have a strongly inrolled apex and produce reproductive structures dorsally on small branchlets which arise either from the margins or the midrib. The groups were also found to form discrete clades on analysis of 18S rRNA sequences. All the members of the first group are endemic to Australia, whereas the second group, designated by the new genus name Adamsiella , contains two previously described New Zealand species and a single Australian representative. In addition, two new species are described in this group from New Zealand. Members of the closely related genus Lenormandiopsis were also examined and the type species, L. latifolia , was found to conform in apex morphology and position of reproductive structures to the genus Lenormandia. Accordingly Lenormandiopsis has been subsumed within Lenormandia. The remaining three members of the former genus Lenormandiopsis , however, were found to differ from both the type species and the genus Lenormandia and consequently have been transferred to the separate genus Geraldia , along with a new species from Geraldton, Western Australia which is designated as the type.     

Lipoxygenase metabolites of arachidonic acid do not induce mucus secretion from rabbit intestinal goblet cells in vitro

Lipoxygenase metabolites of arachidonic acid are effective mucus secretagogues in the respiratory tract but their efficacy in the intestinal tract was unknown. Mucosal explants and sheets of epithelial cells isolated from rabbit small and large intestine were exposed to leukotrienes B4, C4, and D4 and monohydroxyeicosatetraenoic acids 5-HETE, 12-HETE, and 15-HETE. Light and electron microscopic inspection of goblet cells in treated tissues failed to detect evidence of recent compound exocytosis of mucin granules or other morphological evidence of secretory activity. These results indicate that lipoxygenase metabolites are not directly responsible for the increased mucus secretion observed in ulcerative colitis.     

What would it take to describe the global diversity of parasites?

How many parasites are there on Earth? Here, we use helminth parasites to highlight how little is known about parasite diversity, and how insufficient our current approach will be to describe the full scope of life on Earth. Using the largest database of host–parasite associations and one of the world’s largest parasite collections, we estimate a global total of roughly 100 000–350 000 species of helminth endoparasites of vertebrates, of which 85–95% are unknown to science. The parasites of amphibians and reptiles remain the most poorly described, but the majority of undescribed species are probably parasites of birds and bony fish. Missing species are disproportionately likely to be smaller parasites of smaller hosts in undersampled countries. At current rates, it would take centuries to comprehensively sample, collect and name vertebrate helminths. While some have suggested that macroecology can work around existing data limitations, we argue that patterns described from a small, biased sample of diversity aren’t necessarily reliable, especially as host–parasite networks are increasingly altered by global change. In the spirit of moonshots like the Human Genome Project and the Global Virome Project, we consider the idea of a Global Parasite Project: a global effort to transform parasitology and inventory parasite diversity at an unprecedented pace.     

Developmental increase in the amount of rapsyn per acetylcholine receptor promotes postsynaptic receptor packing and stability

Neuromuscular synaptic transmission depends upon tight packing of acetylcholine receptors (AChRs) into postsynaptic AChR aggregates, but not all postsynaptic AChRs are aggregated. Here we describe a new confocal Fluorescence Resonance Energy Transfer (FRET) assay for semi-quantitative comparison of the degree to which AChRs are aggregated at synapses. During the first month of postnatal life the mouse tibialis anterior muscle showed increases both in the number of postsynaptic AChRs and the efficiency with which AChR was aggregated (by FRET). There was a concurrent two-fold increase in immunofluorescent labeling for the AChR-associated cytoplasmic protein, rapsyn. When 1-month old muscle was denervated, postsynaptic rapsyn immunostaining was reduced, as was the efficiency of AChR aggregation. In vivo electroporation of rapsyn-EGFP into muscle fibers increased postsynaptic rapsyn levels. Those synapses with higher ratios of rapsyn-EGFP to AChR displayed a slower metabolic turnover of AChR. Conversely, the reduction of postsynaptic rapsyn after denervation was accompanied by an acceleration of AChR turnover. Thus, a developmental increase in the amount of rapsyn targeted to the postsynaptic membrane may drive enhanced postsynaptic AChRs aggregation and AChR stability within the postsynaptic membrane.     

A quantitative analysis of apolipoprotein binding to SR-BI: multiple binding sites for lipid-free and lipid-associated apolipoproteins

Competitive binding experiments were performed using Y1-BS1 adrenal cells to provide information about the interaction of HDL apolipoproteins with scavenger receptor class B, type I (SR-BI). Exchangeable apolipoproteins apolipoprotein A-I (apoA-I), apoA-II, apoE-2, apoE-3, and apoE-4 as phospholipid complexes bind like HDL3 to SR-BI via their multiple amphipathic alpha-helices; the concentrations required to reduce the binding of HDL3 to SR-BI by 50% (IC50) were similar and in the range of 35-50 microgram protein/ml. In the case of apoA-I, peptides corresponding to segments 1-85, 44-65, 44-87, 149-243, and 209-241 all had the same IC50 as each other (P = 0.86), showing that a specific amino acid sequence in apoA-I is not responsible for the interaction with SR-BI. The distribution of charged residues in the amphipathic alpha-helix affects the interaction, with class A and Y helices binding better than class G* helices. Synthetic alpha-helical peptides composed of either l or d amino acids can bind equally to the receptor. Association with phospholipid increases the amount of apolipoprotein binding to SR-BI without altering the affinity of binding. Lipid-free apolipoproteins compete only partially with the binding of HDL to SR-BI, whereas lipidated apolipoproteins compete fully. These results are consistent with the existence of more than one type of apolipoprotein binding site on SR-BI.     

A note on the use of the Catalasemetre in assessing the quality of milk

The Catalasemetre, for assessing the quality of raw and pasteurized milk, has been studied. No correlation was found between catalase activity and bacterial counts for farm bulk tank milks within the range 5.2 ± 10²-5.4 ± 10⁵ cfu/ml. Similarly, no relation was observed between catalase activity and somatic cell counts of milk (range of counts from 0.08 to 3.5). However, the catalase activity and bacterial count of pasteurized milks which had been pre-incubated at 21.C for 25 h in the presence of crystal violet-penicillin-nisin to inhibit Gram-positive bacterial growth were significantly related. Thus, the use of this pre-incubation procedure coupled with the Catalasemetre to estimate bacterial growth, has potential in assessing the keeping quality of pasteurized milk samples within 25.5 h of production. Results on the thermostability of native milk catalase are also presented.     

Characterization of early B lymphocyte precursors present in long-term bone marrow cultures

Lymphoid precursor cells are present in long-term bone marrow cultures (LTBMC), but their differentiation into mature lymphocytes is blocked. A quantitative assay for B cell precursors in LTBMC, which gives a linear relationship between the number of grafted LTBMC cells and the frequency of B cell colony forming units (CFU-B) in the spleen and bone marrow of immunodeficient CBA/N mice 19 days after reconstitution, is described. Characterization of the B cell precursor indicates that this assay is detecting a very early precursor and not a B lymphocyte or a late pre-B cell. This conclusion is based on the observations that a) pre-B cells transformable by Abelson murine leukemia virus are not present in LTBMC by 3 days postrecharge and CFU-B are absent by 6 days postrecharge; b) late B cell progenitors capable of rapid repopulation of irradiated CBA/N mice are not present in LTBMC, since a lag in the kinetics of B cell reconstitution in animals grafted with LTBMC cells is observed compared with fresh bone marrow cells; c) the B cell precursors in LTBMC have high proliferative potential, since they can stably repopulate recipient mice for at least 8 wk postreconstitution and through two serial passages in irradiated CBA/N recipients; and d) the B cell precursors are large, rapidly sedimenting cells as determined by velocity sedimentation. The serial transplantation experiment further shows that a split is often observed between lymphoid and myeloid reconstituting ability of LTBMC cells. The LTBMC B cell precursor may be a pluripotent stem cell or a lymphoid stem cell, although its differentiative potential remains to be determined.     

The Antiretroviral Lectin Cyanovirin-N Targets Well-Known and Novel Targets on the Surface of Entamoeba histolytica Trophozoites

Entamoeba histolytica, the protist that causes amebic dysentery and liver abscess, has a truncated Asn-linked glycan (N-glycan) precursor composed of seven sugars (Man₅GlcNAc₂). Here, we show that glycoproteins with unmodified N-glycans are aggregated and capped on the surface of E. histolytica trophozoites by the antiretroviral lectin cyanovirin-N and then replenished from large intracellular pools. Cyanovirin-N cocaps the Gal/GalNAc adherence lectin, as well as glycoproteins containing O-phosphodiester-linked glycans recognized by an anti-proteophosphoglycan monoclonal antibody. Cyanovirin-N inhibits phagocytosis by E. histolytica trophozoites of mucin-coated beads, a surrogate assay for amebic virulence. For technical reasons, we used the plant lectin concanavalin A rather than cyanovirin-N to enrich secreted and membrane proteins for mass spectrometric identification. E. histolytica glycoproteins with occupied N-glycan sites include Gal/GalNAc lectins, proteases, and 17 previously hypothetical proteins. The latter glycoproteins, as well as 50 previously hypothetical proteins enriched by concanavalin A, may be vaccine targets as they are abundant and unique. In summary, the antiretroviral lectin cyanovirin-N binds to well-known and novel targets on the surface of E. histolytica that are rapidly replenished from large intracellular pools.Entamoeba histolytica causes amebic dysentery and liver abscess in the developing world (10, 20, 29). We are interested in E. histolytica glycoproteins containing Asn-linked glycans (N-glycans) for numerous reasons. E. histolytica makes an N-glycan precursor that contains 7 sugars (Man₅GlcNAc₂-PP-dolichol) rather than 14 sugars (Glc₃Man₉GlcNAc₂-PP-dolichol) made by most animals, plants, and fungi (21, 31, 44). E. histolytica N-glycans are used for quality control of glycoprotein folding in the endoplasmic reticulum (ER) lumen, and there is positive selection for sites of N-linked glycosylation in secreted and membrane proteins of E. histolytica (5, 11, 53).Unprocessed Man₅GlcNAc₂, by far the most abundant E. histolytica N-glycan, is present on the plasma membrane and vesicular membranes (31). The antiretroviral lectin cyanovirin-N, which is specific for α-1,2-linked mannose present on unprocessed N-glycans, binds E. histolytica N-glycans and forms aggregates or caps on the surface of E. histolytica trophozoites (1, 25, 31, 44, 45). E. histolytica glycoproteins are also capped by the plant lectin concanavalin A (ConA), which has a broader carbohydrate specificity (mannose and glucose) than cyanovirin-N (3, 16, 18, 19). Heavy subunits of the Gal/GalNAc lectin, the most important E. histolytica vaccine candidate, have 7 to 10 potential sites for N-linked glycosylation (32, 39, 43). Inhibition of N-glycan synthesis results in Gal/GalNAc lectins that are unable to bind to sugars on host epithelial cells.Carbohydrates appear to be an important target on the surface of E. histolytica as anti-proteophosphoglycan (PPG) monoclonal antibodies bind to O-phosphodiester-linked glycans and protect animal models from amebic infection (6, 33, 35, 40, 48). Lectin affinity columns are a powerful method for enriching unique parasite glycoproteins that may be identified by mass spectrometry (MS) of tryptic fragments (17, 55). For example, we recently used the plant lectin wheat germ agglutinin to dramatically enrich glycoproteins with short N-glycans of Giardia (42).The goal of the present studies was to explore further the interaction of the antiretroviral lectin cyanovirin-N with E. histolytica trophozoites in vitro. Questions asked included the following: Are E. histolytica glycoproteins with N-glycans replenished on the plasma membrane after capping with cyanovirin-N? What is the effect of cyanovirin-N capping on other amebic virulence factors and/or vaccine candidates (e.g., the Gal/GalNAc lectin and PPG)? Is capping by cyanovirin-N mediated by actin, as described for capping by the Gal/GalNAc lectin and ConA? What is the effect of the cyanovirin-N on amebic phagocytosis of mucin-coated beads, a surrogate assay for virulence? Which trophozoite glycoproteins are potential targets of cyanovirin-N (identified by mass spectrometry of lectin-enriched E. histolytica proteins)? Are any of them potential vaccine candidates?