The nitrogen cycle in shallow water sediment systems of rice fields Part III: The influence of N-application on the yield of rice

Fertilizer application to rice-fields in the river-deltas in the Mediterranean area is a potential menace for wildlife protection, through eutrophication.Fertilizer use shows a trend of increasing rates of N application. A rate for N of 200 kg ha^–1 has become normal and a rate of 400 kg ha^–1 has already been recorded.Denitrification causes large losses of N with the result that more fertilizer is applied. This is especially true for the Camargue (S-France), where N is applied long before the rice (Aryza sativa) can take it up.Therefore we have tried to develop techniques which need the application of smaller amounts of N which are used more efficiently. In order to do this we tried to establish a N budget for rice-fields.Experiments were therefore set up in the field (plots of 550 m²) and in pots (2–3 l). Our results suggest that a late application of N (e.g. when the rice shows signs of N-deficiency by becoming yellowish), but at lower concentrations (70 kg ha^–1) can produce the same ultimate yield. The introduction of carp without any further input of N produced the same final yield.The N budget shows that 15±1.5 g m^–2 of N is needed for a normal crop. N losses due to denitrification may be as high as 12.2–13.6 g m^–2 of N. The input by irrigation water may provide up to about 20% of the input; N fixation is negligible. We estimate that 25–50% of the N missing in the budget comes from minderalization of the organic N pool in the soil. Denitrification may render part of this pool bio-available by oxidation. In sum, this work has revealed some surprising effects with potentially important consequences for farming practice and, in consequence, for conservation.     

Definition of meningococcal class 1 OMP subtyping antigens by monoclonal antibodies

The subtypes of meningococci are defined by antigenic determinants on the class 1 outer membrane proteins. The established subtypes, designated by P1 and a number according to the prototype reference strain on which they were first recognized by monoclonal antibodies, includes P1.2, P1.9, P1.15 and P1.16. We have investigated more prototype reference strains, using new monoclonal antibodies, and identified the new subtypes P1.1, P1.6 and P1.1,16. The P1.1,16 epitope is found on both the P1.1 and the P1.16 reference strains, but not on all P1.1 and P1.16 strains and can occur independently from the P1.1 and the P1.16 epitopes. It appears that class 1 outer membrane proteins contain at least two independent subtype-specific epitopes. For clarity, we now redefine P1.1,16 as P1.7, permitting thus the identification of strains of P1.1, P1.1,7, P1.7, P1.7,16 and P1.16 subtypes. It can clearly be expected that more class 1 outer membrane protein determinants will be recognized as more monoclonal typing antibodies are produced. The monoclonal antibodies now available to us can subtype 80-90% of group B and C meningococci; they also react with group A meningococci, but not with other Neisseriae. The immunological dissection of these subtyping antigens will improve our understanding of the relationship between components of the bacteria and the induction or prevention of disease.     

The Chlamydomonas cell wall degrading enzyme, lysin, acts on two substrates within the framework of the wall

The Chlamydomonas cell wall is a multilayered, extracellular matrix containing 20-25 proteins and glycoproteins, many of which are highly enriched in hydroxyproline. 80-90% of the wall protein is located in a crystalline portion of the wall that is soluble in sarkosyl-urea solutions as well as in chaotropic salts. Although the wall has no cellulose it contains a noncrystalline, highly insoluble framework portion that is responsible for the integrity and overall shape of the wall. In the present report we show that the framework of the wall is composed of two components that are acted upon by lysin, a wall degrading enzyme released by mating gametes. One, which makes up the major portion of the framework, is insoluble upon boiling in SDS-PAGE sample buffer. Lysin treatment of this portion leads to its physical degradation and the concomitant appearance of several SDS-dithiothreitol-soluble polypeptides ranging in relative molecular mass from greater than 400,000 to less than 60,000. The second component is the flagellar collar. This hollow cylinder composed of striated fibers aligned in parallel array serves as the tunnel in the wall through which the flagella protrude. Our evidence indicates that the primary collar polypeptide is a 225,000-Mr molecule that itself has at least two functional domains. One domain, contained in a 185,000-Mr fragment, permits the self-association of the molecules to form the main body of the collar. The second part of the molecule anchors the collar to the wall framework via sarkosyl-urea-insensitive, SDS-dithiothreitol-sensitive linkages.     

The thermal induced helix--beta transition of poly(N epsilon-methyl-L-lysine) and poly(N delta-ethyl-L-ornithine) in aqueous solution

Uncharged poly(N^ε-methyl-L -lysine) (PMLL) and its isomer, poly(N^δ-ethyl-L -ornithine) (PELO), in alkaline solution (pH ca. 12) undergo a helix-to-β transition upon mild heating at 50°C or higher in a manner similar to that of poly(L -lysine) (PLL). The rate of conversion follows the order: PMLL < PELO < PLL. The helix can be regenerated upon cooling near zero degrees, for instance, after more than 12 hr at 2°C. At concentrations less than 0.02% the β form is intramolecular, but at higher concentrations both intra- and intermolecular β forms are generated. Poly(N^δ-methyl-L -ornithine) (PMLO), an isomer of PLL, behaves like poly(L -ornithine); uncharged PMLO in alkaline solution is partially helical and becomes disordered at elevated temperatures.     

Transient and long-term differential modulations of branched-chain α-keto acid decarboxylase activity in hypophysectomized rats

Hypophysectomy caused a marked but transient increase in branched-chain α-keto acid decarboxylase activities in rat liver mitochondria, peaking at about nine days post-surgery. The magnitude of increase is different for each of the three branched-chain α-keto acids. The activities then fall to a new steady state in three weeks with α-ketoisovalerate decarboxylase activity within the normal range, α-keto-β-methylvalerate decarboxylase activity at twice normal, and α-ketoisocaproate decarboxylase activity decreased to a level too low for accurate measurements.     

Genetic and Physical Mapping of the Mcra (Rgla) and Mcrb (Rglb) Loci of Escherichia Coli K-12

We have genetically analyzed, cloned and physically mapped the modified cytosine-specific restriction determinants mcrA (rglA) and mcrB (rglB) of Escherichia coli K-12. The independently discovered Rgl and Mcr restriction systems are shown to be identical by three criteria: 1) mutants with the RglA- or RglB- phenotypes display the corresponding McrA- or McrB- phenotypes, and vice versa; 2) the gene(s) for RglA and McrA reside together at one locus, while gene(s) for RglB and McrB are coincident at a different locus; and 3) RglA+ and RglB+ recombinant clones complement for the corresponding Mcr-deficient lesions. The mcrA (rglA) gene(s) is on the excisable element e14, just clockwise of purB at 25 min. The mcrB (rglB) gene(s), at 99 min, is in a cluster of restriction functions that includes hsd and mrr, determinants of host-specific restriction (EcoK) and methyladenine-specific restriction respectively. Gene order is mcrB-hsdS-hsdM-hsdR-mrr-serB. Possible models for the acqusition of these restriction determinants by enteric bacteria are discussed.