Diet changes in the carbon and nitrogen content of the copepod Metridia lucens

Diel changes in the near-surface (0–50 m) abundance, prosomelength, and carbon and nitrogen content of the copepod Metridialucens were measured in Deep Cove, Doubtful Sound, New Zealand(45°27'S, 167°9'E) between 3 and 6 September 1996. Metridialucens showed maximal abundance a night, suggesting a patternof normal diel vertical migration (DVM). The change in abundancesuggested that the descent of the population occurred –1h prior to dawn and the ascent –1 h after dusk. However,a proportion of the population remained near the surface duringthe day. Although there was no diel pattern in the prosome lengthof M.lucens collected near the surface, there was a marked dielcycle in the measured carbon and nitrogen contents, with maximalvalues being measured towards the end of the night prior tothe downward migration. We suggest that this diet cycle in themeasured elemental content was caused by DVM occurring morestrongly in those animals which had a better body condition,i.e. a higher elemental content per unit length.     

Aphanizomenon ovalisporum (Forti) in Lake Kinneret, Israel

The filamentous cyanobacterium Aphanizomenon ovalisporum wasobserved for the first time in Lake Kinneret in August 1994and formed a prominent bloom from September through October.Aphanizomenon ovalisporum reappeared in diminished amounts inthe summer and fall of 1995. These events are the first recordof significant quantities of a potentially toxic nitrogen-fixingcyanobacterium in this lake. No definite provenance of inoculumhas been identified, although A.ovalisporum was also observedin a newly reflooded area (Lake Agmon) in the catchment. Unusuallyhigh water temperatures and low wind inputs were observed priorto and during the A.ovalisporum bloom period. These, togetherwith possibly enhanced availability of phosphorus or other growthfactors, may have contributed to the cyanobacterium growth in1994. Phosphorus limi tation, as indicated by high cellularalkaline phosphatase activity, the onset of stormy conditionsand a fall in water temperatures led to the demise of the 1994bloom. Although the A. ovalisporum bloom in 1994 had no seriousdirect impact on water quality, the continued presence of apotentially toxic cyanobacterium in Lake Kinneret, a major nationalwater supply source, is a cause for serious concern.     

The Pitcairn Islands, South Pacific Ocean: plate tectonic and climatic contexts

The remote Pitcairn Group in the South Pacific Ocean comprises a volcanic island (Pitcairn Island), two low coral atolls (Oeno, Ducie) and a raised coralline island (Henderson Island). The geological history of these islands, on anomalously thin oceanic lithosphere, is related to the development of two subparallel island chains (Oeno-Henderson-Ducie; Pitcairn) associated with intra-Pacific plate 'hotspot' activity; the surface manifestation of this activity has been partly determined by structural lineations in the plate inherited from past plate history. The climate of the Pitcairn Islands is determined by the position of the subtropical high pressure system and the South Pacific Convergence Zone. Variations in the strength of this atmospheric circulation system, measured by changes in the Southern Oscillation index of pressure difference, provide a partial explanation of the long-term variability of mean annual rainfall at Pitcairn Island. Knowledge of past climates in the Pitcairn Group remains speculative. Maps of the Pitcairn Islands and a report of climate at Henderson Island (2/91-1/92) are included in the paper.     

Analysis of water in Autonomous Biological Systems (ABS) samples.

Several soluble components, peptidase and amino acids, and carbon isotopic ratio in the water retrieved from flight experiments of Autonomous Biological Systems (ABS) as well as ground control samples are analyzed to interpret the condition, dynamics, material balance of the ABS ecosystems. Organic carbons in flight samples were found to be more abundant compared with the control ones, which suggested the uniform ecosystems in low gravity might easily dissolve more soluble components. The Mir-1997 flight sample showed higher C/N ratio probably because of the dissolution of carbon-rich plant materials.     

Dipeptide derivative synthesis catalyzed by Pseudomonas aeruginosa elastase.

Pseudomonas aeruginosa elastase was used to synthesize various N-protected dipeptide amides. The identity of the products was confirmed by FAB(+)-MS. After recrystallization, the yield of their synthesis was calculated, their purity was checked by RP-HPLC and their melting point was measured. With regard to the hydrolysis, it is well-established that the enzyme prefers hydrophobic amino acids in P'1 position and it has a wide specificity for the P1 position. This specificity was demonstrated to be quite unchanged when comparing the initial rates of peptide bond formation between different carboxyl donors (Z-aa) and nucleophiles (aa-NH2). The elastase, but not the thermolysin, was notably able to incorporate tyrosine and tryptophan in P'1 position. Furthermore, synthesis initial rates were at least 100 times faster with the elastase. To overcome the problematic condensation of some amino acids during chemical peptide synthesis, it has been previously suggested that enzymatic steps can combine with a chemical strategy. We demonstrated that the elastase readily synthesizes dipeptide derivatives containing various usual N-protecting groups. It was especially able to condense phenylalaninamide to Fmoc- and Boc-alanine. Increasing interest in peptides containing unnatural amino acids led us to try the elastase-catalyzed synthesis of Z-dipeptide amides including those amino acids in the P1 position. A synthesis was demonstrated with alphaAbu, Nle, Nva and Phg.     

The light organ symbiont Vibrio fischeri possesses two distinct secreted ADP-ribosyltransferases.

We have previously described the purification, cloning, and initial characterization of a secreted ADP-ribosyltransferase, halovibrin (gene designation hvn), from the luminescent light organ symbiont Vibrio fischeri. This report describes a strategy for overexpression of halovibrin, the production and refinement of antihalo-vibrin antisera, and the molecular biological construction of a V. fischeri halovibrin null strain. Biochemical analysis of this mutant revealed that V. fischeri hvn null still possessed ADP-ribosyltransferase activity and that this activity is immunologically, genetically, and structurally distinct from the previously described enzyme. This unusual finding, of two ADP-ribosyltransferase enzymes produced by a microorganism, is complemented by the details of the purification to apparent homogeneity and in vitro regulation of this new protein, halovibrin-beta.