Active chitinases in the apoplastic fluids of healthy white lupin (Lupinus albus L.) plants

Acidic exocellular class III chitinase (EC 3.2.1.14) was previously identified in healthy white lupin (Lupinus albus L.) plants and suspension-cultured cells by N-terminal microse-quencing. In this study, the detection of chitinase activity with Remazol Brilliant Violet 5R (RBV)-labelled chitin derivatives is described. Chitinase activity was observed in protein fractions of cytoplasmic or exocellular origin from roots, hypocotyls, cotyledons, and leaves of healthy white lupin plants. Using isoelectrofocusing followed by a new overlay technique with carboxymethyl chitin-RBV conjugate-containing gel, up to six different chitinase isoforms were visualised. Their activity was distributed fairly evenly within a plant with acidic isoforms predominating in cell walls and basic (or neutral) ones found intracellularly. Exocellular location of some chitinase isoforms were also confirmed by detection of their activities in intercellular washing fluids from white lupin tissues. Chitinase activity was demonstrated in culture filtrates and cell walls of suspension-cultured white lupin cells.     

中国毛霉的三个新记录种

报道了中国毛霉属的三个新记录并对它们进行了描述和简短的讨论。它们是：Mucor hiemalis f.luteus, Mucor racemosus f. chibinensis.和Mucor racemosus f. sphaerosporus.     

共培养条件下绿木霉对褐环乳牛肝菌产酶的诱导效应

为了探讨绿木霉与褐环乳牛肝菌的互作机理,在体外共培养条件下,采用光学显微镜和扫描电镜对二者生长重叠部分进行体外观察,发现二者生长无相互影响,在营养生长方面几乎不存在竞争关系。为进一步揭示绿木霉与褐环乳牛肝菌的互作机制,采用体外诱导和生物化学等方法,向褐环乳牛肝菌发酵液中加入灭活绿木霉菌丝诱导物,每天对发酵液中的多酚氧化酶、几丁质酶、漆酶和中性蛋白酶等酶活性进行检测。试验结果表明,绿木霉诱导褐环乳牛肝菌产漆酶能力最强;在整个共培养过程中,多酚氧化酶和漆酶活力始终处于较高水平,在诱导培养第6天,这两种酶活性升至最高,分别达到25.2U/mL和1 580U/mL;灭活绿木霉菌丝对褐环乳牛肝菌几丁质酶的诱导具有“瞬时性”,在诱导培养第2天即检测到较高的几丁质酶活性;中性蛋白酶的活性变化基本上呈先上升后下降的规律,且能增大褐环乳牛肝菌中性蛋白酶的固有产量,形成“叠加效果”。综上所述,绿木霉对褐环乳牛肝菌几乎不存在营养竞争关系,但其灭活菌丝体对褐环乳牛肝菌发酵液的多种酶活性存在诱导增效作用。     

Plant invasion alters nitrogen cycling by modifying the soil nitrifying community

Plant invasions have dramatic aboveground effects on plant community composition, but their belowground effects remain largely uncharacterized. Soil microorganisms directly interact with plants and mediate many nutrient transformations in soil. We hypothesized that belowground changes to the soil microbial community provide a mechanistic link between exotic plant invasion and changes to ecosystem nutrient cycling. To examine this possible link, monocultures and mixtures of exotic and native species were maintained for 4 years in a California grassland. Gross rates of nitrogen (N) mineralization and nitrification were quantified with ¹⁵N pool dilution and soil microbial communities were characterized with DNA‐based methods. Exotic grasses doubled gross nitrification rates, in part by increasing the abundance and changing the composition of ammonia‐oxidizing bacteria in soil. These changes may translate into altered ecosystem N budgets after invasion. Altered soil microbial communities and their resulting effects on ecosystem processes may be an invisible legacy of exotic plant invasions.     

Interactions between bacterial membranes and peptidolipids: Lysis of Micrococcus luteus protoplasts by derivatives of peptidolipidic antibiotics from Bacillus subtilis

The lysis of protoplasts of Micrococcus luteus has been tested with various derivatives of three peptidolipidic antibiotics: iturin A, mycosubtilin and bacillomycin L. The lytic activity is dependent to the nature of the substituting group and to the position of the substituted aminoacid residue. The acetylation of OH groups leads to a decrease of the lytic activity of the natural antibiotics. The methylation of aspartyl residues of bacillomycin L gives a strong lytic activity while natural bacillomycin L has no lytic activity. The methylation of the tyrosyl residue enhances the lytic activities of iturin A and of bacillomycin L-dimethyl ester and reduces that of mycosubtilin.Correlations between the structures of derivatives and their lytic action on M. luteus protoplasts are discussed.     

Biosynthesis,cDNA and amino acid sequences of a precursor of conglutin δ, a sulphur-rich protein from Lupinus angustifolius

The biosynthesis of conglutin has been studied in developing cotyledons of Lupinus angustifolius L. Precursors of conglutin formed the major sink for [³⁵S]-cysteine incorporated by developing lupin cotyledons, and these precursors were rapidly sequestered into the endoplasmic reticulum. The sequence of a cDNA clone coding for one such precursor of conglutin was determined. The structure of the precursor polypeptide for conglutin predicted from the cDNA sequence contained an N-terminal leader peptide of 22 amino acids directly preceding a subunit polypeptide of M _r 4520, together with a linking region of 13 amino acids and a subunit polypeptide of M _r 9558 at the C-terminus. The amino acid sequence predicted from the cDNA sequence showed minor variations from that established by sequencing of the protein purified from mature dried seeds (Lilley and Inglis, 1986). These were consistent with the existence of a multi-gene family coding for conglutin . Comparison of the sequences of conglutin with those of other 2S storage proteins showed that the cysteines involved in internal disulphide bridges between the mature subunits of conglutin , were maintained throughout this family of proteins but that little else was conserved either at the protein or DNA level.     

Biosorption of Strontium from Aqueous Solutions by Micrococcus luteus Sr02

Although strontium (Sr²⁺) is found in soils, sediments and surface waters, there is limited evidence about its biosorption. In this study, a surface water strain being highly tolerant to Sr²⁺ was isolated and identified as Micrococcus luteus Sr02 by using 16S rRNA sequencing. Biosorption behavior and mechanisms of Sr²⁺ by M. luteus Sr02 were investigated through batch experiments, zeta potential measurements, Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that M. luteus Sr02 have potential to sorb Sr²⁺ and can be used efficiently for the removal of Sr²⁺ from aqueous solutions.     

Sensitivity of different Lupinus species to calcium under a low phosphorus supply

To study mechanism underpinning the calcifuge habit of some Lupinus species, especially under low‐phosphorus (P) conditions, Lupinus species that were likely to respond differently to calcium (Ca) availability were assembled, and the sensitivity to Ca under a low‐P supply was assessed. Seven Lupinus species (9 genotypes, L. albus L. cv Kiev, L. albus L. P26766, L. angustifolius L. cv Mandelup, L. angustifolius L. P26723, L. luteus L. cv Pootalong, L. hispanicus ssp. bicolor Boiss. and Reut. P22999, L. pilosus Murr. P27440, L. cosentinii Guss. P27225, and L. atlanticus Gladst. P27219) were grown hydroponically at 10 or 6000 μM Ca. Leaf symptoms, gas exchange and biomass were recorded; leaf and root nutrient concentrations were analysed, and the leaf cell types in which Ca and P accumulated were determined using elemental X‐ray microanalyses. Calcium toxicity was demonstrated for L. angustifolius P26723, L. hispanicus ssp. bicolor. P22999, and L. cosentinii P27225, whereas the other species were tolerant of a high Ca supply under low‐P conditions. In addition, genotypic differences in Ca toxicity were found within L. angustifolius. Most Ca accumulated in the mesophyll cells in all species, whereas most P was located in epidermal cells.