Root hydrocarbons as potential markers for determining species composition

Grasslands can be a complex mixture of plant species. A method is described to allow the identification of both roots and shoots of five different grass species, thus permitting greater knowledge about whole plant allocation and competition in mixed pastures. The five species were Lolium perenne, Festuca ovina, Festuca rubra, Poa trivialis and Agrostis capillaris. N‐alkanes with odd‐numbers of carbon atoms in the chains predominate in plants and in the five grass species studied, concentrations of alkanes of chain length of C₂₉, C₃₁ and C₃₃ were highest. Average concentrations of C₂₇‐C₃₃ alkanes in shoots and roots were 187 and 11 mg kg ^{? 1}, respectively. This wide range of values required considerable modifications to the method of analysis, including expressing concentrations on an organic matter basis and scaling‐down the procedure. The n‐alkane concentrations in roots are different from those in shoots and therefore values from shoots cannot be used to predict the composition in roots. Using a canonical variate analysis, all five grass species could be separated using concentrations of C₂₆, C₃₁ and C₃₃ values in the roots. The greatest difference occurred between A. capillaris and the others, whereas discrimination was least between the two Festuca species. Defoliation had contrasting effects on the concentration of a few n‐alkanes, but not in the n‐alkanes used to discriminate between grass species. Alkane analysis shows great potential as a method to quantify the species composition of the root biomass beneath mixed pasture species.     

Bacterial adsorption to thermoresponsive polymer surfaces

The ability of microorganisms to `recognise' a change in the hydrophobicity/hydrophilicity balance of the surface was demonstrated using thermoresponsive poly(N-isopropylacrylamide) co-polymers with different Lower Critical Solution Temperatures. The polymers were grafted onto hydrolysed glass under well controlled conditions and the adhesion was followed using ¹³C-labelled Listeria monocytogenes. Attachment of the bacteria was found to be directly affected by the polymer transition from a hydrophilic to a hydrophobic state but by less than one order of magnitude.     

Bacterial adhesion at synthetic surfaces.

A systematic investigation into the effect of surface chemistry on bacterial adhesion was carried out. In particular, a number of physicochemical factors important in defining the surface at the molecular level were assessed for their effect on the adhesion of Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, and Escherichia coli. The primary experiments involved the grafting of groups varying in hydrophilicity, hydrophobicity, chain length, and chemical functionality onto glass substrates such that the surfaces were homogeneous and densely packed with functional groups. All of the surfaces were found to be chemically well defined, and their measured surface energies varied from 15 to 41 mJ. m(-2). Protein adsorption experiments were performed with (3)H-labelled bovine serum albumin and cytochrome c prior to bacterial attachment studies. Hydrophilic uncharged surfaces showed the greatest resistance to protein adsorption; however, our studies also showed that the effectiveness of poly(ethyleneoxide) (PEO) polymers was not simply a result of its hydrophilicity and molecular weight alone. The adsorption of the two proteins approximately correlated with short-term cell adhesion, and bacterial attachment for L. monocytogenes and E. coli also correlated with the chemistry of the underlying substrate. However, for S. aureus and S. typhimurium a different pattern of attachment occurred, suggesting a dissimilar mechanism of cell attachment, although high-molecular-weight PEO was still the least-cell-adsorbing surface. The implications of this for in vivo attachment of cells suggest that hydrophilic passivating groups may be the best method for preventing cell adsorption to synthetic substrates provided they can be grafted uniformly and in sufficient density at the surface.     

Changing land management of lowland wet grasslands of the UK: impacts on snipe abundance and habitat quality

Snipe Gallinago gallinago breeding on lowland wet grasslands in England have undergone widespread and dramatic declines in abundance and distribution since at least the 1970s. There are many potential drivers of the decline but reductions in habitat quality, driven by land management, are often proposed as a contributing factor in the historical declines of breeding waders. Breeding snipe are now restricted to a few key places such as nature reserves and environmentally sensitive areas where management for breeding waders is implemented. On average, populations have continued to decline, even in these key areas, though population trends vary from a decline of 98% to an increase of 61% between the early 1990s and 2006. We examined the relationship between regional variation in snipe population trends and soil conditions, other habitat features and land management. Snipe were more likely to persist in fields where the soil conditions were wet and soft. Fields are wetter and softer now than in the early 1990s and management influenced these conditions. Soil softness increased with decreasing grazing pressure and increasing surface flooding. Soil moisture increased with surface flooding and was higher in organic soils. Changes in field condition were consistent with decreases in grazing pressure and increases in surface flooding. In spite of habitat condition being altered in a way that should have been beneficial to snipe, the numbers have continued to decline. Thus, it is unlikely that the measures of habitat condition examined here have been the driver of the decline and other factors must be involved. Research efforts should now focus on alternative explanations of the decline, for example, changes in other key aspects of habitat quality such as prey abundance, or changes in snipe productivity or mortality.     

Wd(a+) red blood cells in two sisters of a Hei//om Khoisan family in Namibia

Two sisters in a Hei//om family of the southern African Khoisan race in Namibia were found to have Wd(a+) red blood cells. Wda is a low-frequency antigen identified so far only in a European family in Canada and a family in Holland. The Wda gene may have had an independent origin in the Khoisan. Alternatively, the Hei//om population may have acquired it through miscegenation.     

Root Penetration by Meloidogyne incognita Juveniles Infected with Bacillus Penetrans

Bacillus penetrans inhibited penetration by Meloidogyne incognita second-stage juveniles (J2) into tomato roots in the laboratory and greenhouse. Spores from this Florida population of B. penetrans attached to J2 of M. javanica, M. incognita, and M. arenaria. A greater proportion of J2 of M. javanica were infected than were J2 of either M. incognita or M. arenaria, and a greater number of spores attached to M. incognita than to M. arenaria.     

Fine specificity of antigen recognition by T cell hybridoma clones specific for poly-18: a synthetic polypeptide antigen of defined sequence and conformation

Antigen-specific T cell blasts to poly-18, a polypeptide antigen of defined sequence and conformation, were generated from lymph nodes of antigen-primed BALB/cCr mice. These blasts were fused with the BW5147 thymoma to obtain anti-poly-18-reactive T cell hybridomas. All of the hybridomas were IAd-restricted and secreted IL2 in the presence of IAd/poly-18. On the basis of fine specificity analysis, these hybridomas were classified into two groups. Group A hybridomas recognized a minimal peptide sequence of Glu-Tyr-Lys-(Glu-Tyr-Ala)3-Glu-Tyr-Lys, whereas Group B needed the sequence Glu-Tyr-Ala-(Glu-Tyr-Ala)3-Glu-Tyr-Lys/Ala for activation. Three critical residues were identified in Group A hybridomas: the alanine residue at position 9, the carboxy terminal lysine, and the lysine at position 3. In Group B hybridomas, the alanine at position 3 was found to be the critical residue. We suggest that the amino acid residue at position 3 (lysine/alanine) is the T cell receptor contact residue on the poly-18 antigen in BALB/cCr mice.