The distribution of Minuartia verna and Thlaspi alpestre in the British Isles in relation to 13 soil metals

The plant-communities from habitats of the metallophyte species Minuartia verna and Thlaspi alpestre (T. caerulescens) at sites disturbed and undisturbed by mining are described. Four communities were delineated by cluster and principal component analysis. Group 1 comprised species-poor communities on disturbed non-calcareous soils; group 2, relatively species-rich communities on disturbed calcareous soils; group 3, species-rich communities in the main on undisturbed calcareous soils. Group 4 consisted of species-rich communities with an alpine element, in damp habitats on base-rich soils derived from igneous rocks. Total and exchangeable elements As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn were determined for the soils of these sites. Levels of soil Ca, Cd, Pb and Zn accounted for most of the variation along the first axis of the PCA and soil nutrient levels were probably the main predictor along the second.Abbreviations PCA Principal Component Analysis     

Dissection of functional domains in phage fd adsorption protein. Discrimination between attachment and penetration sites

We constructed a set of deletion mutants in the attachment protein of phage fd. These mutants lack sequences coding for sections in the amino-terminal half. All the mutants that comprise a leader sequence are incorporated into phage particles. Our data strongly suggest a bipartite organization of the amino-terminal domain with (1) a region for receptor recognition and (2) a region that is necessary for penetration of the DNA into the host cell. These regions were mapped. Some evidence suggesting different roles for gene 3 protein in penetration of the outer and inner membrane are discussed. We demonstrate that the phenotypes caused by gene 3 protein in host cells can be subdivided into two groups with different sequence requirements: (1) phenotypes related to outer membrane disturbance; and (2) phenotypes related to the tolQRA transport system.     

Subcellular localization of the major pneumococcal autolysin: a peculiar mechanism of secretion in Escherichia coli

The major pneumococcal autolysin (N-acetylmuramoyl-L-alanine amidase) has been localized in the cellular envelope of Streptococcus pneumoniae and Escherichia coli by using immunocytochemical labeling on ultrathin sections and whole-mounted cells. Cell fractionation experiments in E. coli confirmed the peripheral localization of the pneumococcal amidase and suggested that this enzyme is weakly bound to the outer face of the cytoplasmic membrane. This interaction does not depend on the presence of choline but represents an intrinsic property of the amidase. The autolysin, that is synthesized without any N-terminal signal sequence (García, P., García, J. L., García, E., and López, R. (1986) Gene (Amst.) 43, 265-272) was not processed during translocation. A new regulatory mechanism that might be specific for bacterial autolysins is discussed.     

Regulation, clinical and biological significance of cathepsin D in breast cancer

The lysosomal protease, pro-cathepsin D, is overexpressed and secreted by human breast cancers. In estrogen-responsive breast cancer cell lines, estrogens and growth factors stimulate cathepsin D expression through distinct mechanisms. Clinical studies indicate that high cathepsin D concentration in primary breast cancers is correlated with an increased risk of metastasis and particularly useful to orientate node-negative tumors towards an adjuvant therapy.     

Quantitative phenotypical expression of three mutant genes in barley and the basis for defining an ideotype for Mediterranean environments

Summary Three mutants induced in the two-rowed barley variety Beka and their three binary recombinants have been used in an attempt to define an ideotype suitable for Mediterranean agroclimatic conditions. Physiological methods (classical plant growth analysis) together with the study of genotype x environment interaction for grain yield were used to characterize the genotypes. That characterization brought out the huge phenotypical variation produced by only three mutant genes, suggesting that single Mendelian genes may alone explain the quantitative variation, including grain yield, without the necessity of using the polygenic concept. The genotype best adapted to the environments studied is later in heading and has shorter straw and denser spikes than Beka; it also has higher inverse of leaf area rate and grain: leaf area ratio, a lower rate of leaf senescence, and a shorter grain filling period than the original variety.     

Production of staphylococcal enterotoxins C1 and C2 and thermonuclease throughout the growth cycle

Synthesis of enterotoxins C1 and C2 and thermonuclease throughout the growth cycle was investigated with Staphylococcus aureus type strains FRI137 and FRI361 and S. aureus isolates M5 (C1) and L2 (C2) of animal origin. Both enterotoxins were produced during the exponential growth phase or at the beginning of the stationary phase. The minimal incubation time (7 to 12 h) and the lowest population (10(7) to 2 x 10(9) CFU/ml) associated with detectable enterotoxin (1 to 6.5 ng/ml) were related to the total amount of toxin produced after 24 h. Thermonuclease was detected in all samples whenever enterotoxins were detected. Furthermore, strain FRI137 produced thermonuclease earlier and at lower cell populations than it did enterotoxin C1. Patterns of enterotoxin and thermonuclease synthesis did not correlate. The concentration of toxins increased throughout the growth cycle, while the concentration of thermonuclease remained constant during the last hours of the growth cycle.