Production Dynamics and Characterization of Chitinolytic System of Streptomyces sp. NK1057, a Well Equipped Chitin Degrader

Streptomyces sp. NK 1057 produced four extracellular chitinases. Two (62 and 48 kDa) were endochitinaseswhile the other two (35 and 28 kDa) had chitobiosidaseactivity. Chi62 was produced in early growth phase whereas the other three were produced later. Chi48 was optimally active at pH 4.0 and 60 °C whereas Chi35 was optimally active at pH 6.0 and 40 °C. Both the enzymes had fairly good pH and temperature stability up to 50 °C, with Chi48 being more thermostable than Chi35. Chi48 was significantly inhibited by N-acetylglucosaminebut not by Hg²⁺ and the reverse was true for Chi35. Chi48 and Chi35 had isoelectric points of 5.1 and 6.0 and the N-terminal amino acid sequence of Chi35 determined uptofour amino acids, was Gln–Ser–Pro– Gly. Chi62 and Chi48 were able to inhibit the germination of Fusariumoxysporum spores by 57.4 and 61.2% respectively whereas; Chi35 and Chi28 did so by only 14.1 and 3.8%, suggesting endochitinaseto possess antifungal activity. Only Chi28 exhibited a lytic activity, 0.022 U ml^–1, towards Micrococcus lysodeikticus cells.     

Nitrogen and phosphorus content of some temperate and tropical freshwater fishes

The nitrogen and phosphorus content of two temperate fishes, Rutilus rutilus and Perca fluviatilis , and six tropical fishes, Oreochromis niloticus , Cichla monoculus , Serrassalmus rhombeus , Plagioscion squamosissimus , Prochilodus brevis and Hoplias malabaricus , were investigated to test the hypothesis that variation in body P content and N:P ratio is related to body size. Regressions of %P and N:P ratios against fish size (length and mass) confirmed the hypothesis for P. fluviatilis and P. squamosissimus , suggesting that body size is an important factor driving body P content and N:P ratios in some fishes. Moreover, significant increases in %N and N:P ratio with body size was found for H. malabaricus , a common piscivorous fish of the Neotropics. Interspecific variation in %P and N:P ranged two-fold and significant differences ( P < 0·05) were found among the tested species. The mean ± s . d . elemental content across all fishes ( n = 170) was 10·35 ± 1·29% for N and 3·05 ± 0·82% for P, while the N:P ratio was 8·00 ± 2·14. Data on fish body nutrient content and ratio will improve parameterization of bioenergetics and mass balance models and help clarify the role of fishes in nutrient cycles in both temperate and tropical freshwaters.     

Interactions of a Bacterial RND Transporter with a Transmembrane Small Protein in a Lipid Environment

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Multiple Sequence Variants in STAC3 Affect Interactions with CaV1.1 and Excitation-Contraction Coupling

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Periodic Oscillations of Myosin-II Mechanically Proofread Cell-Cell Connections to Ensure Robust Formation of the Cardiac Vessel

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Rational modifications,synthesis and biological evaluation of new potential antivirals for RSV designed to target the M2-1 protein

Respiratory syncytial virus (RSV) is the main cause of lower respiratory tract diseases in infants and young children, with potentially serious and fatal consequences associated with severe infections. Despite extensive research efforts invested in the identification of therapeutic measures, no vaccine is currently available, while treatment options are limited to ribavirin and palivizumab, which both present significant limitations. While clinical and pre-clinical candidates mainly target the viral fusion protein, the nucleocapsid protein or the viral polymerase, our focus has been the identification of new antiviral compounds targeting the viral M2-1 protein, thanks to the presence of a zinc-ejecting group in their chemical structure. Starting from an anti-RSV hit we had previously identified with an in silico structure-based approach, we have designed, synthesised and evaluated a new series of dithiocarbamate analogues, with which we have explored the antiviral activity of this scaffold. The findings presented in this work may provide the basis for the identification of a new antiviral lead to treat RSV infections.     

Optical Feedback Loop Involving Dinoflagellate Symbiont and Scleractinian Host Drives Colorful Coral Bleaching

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Dietary self-selection for vitamins and lipid by larvae of the corn earworm, Heliothis zea

Last instar larvae of the corn earworm, Heliothis zea (Boddie) (Lepidoptera: Noctuidae), require lipid and certain vitamins in their diet in order to complete larval development. When experimental larvae were offered two nutritionally incomplete diets, each lacking a different one of the requirements, they invariably ate from both diets, self-selecting a mixture that was nutritionally superior to either diet alone.

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Résumé Les chenilles de dernier stade d' H. zea (Boddie) (Lep.:Noctuidae) ont besoin de lipides et de certaines vitamines dans leur régime alimentaire, probablement parce qu'elles n'en contiennent pas assez provenant des stades précédents. Quand deux régimes incomplete ont été fournis aux chenilles (chacun privé différemment de l'un de ces consituants: lipide, chlorure de choline ou un ensemble de vitamines), elles ont consommé systématiquement des deux régimes et autosélectionné un aliment de qualité supèrieure à celle de chaque régime séparément. D'un autre côté, les chenilles témoins à qui on a offert deux régimes identiques et nutritionnellement complets, ont choisi apparemment leur aliment au hasard, et presque la moitié d'entre elles ont consommé exclusivement on presque exclusivement l'un des régimes, tandis que l'autre moitié a choise exclusivement or presque exclusivement l'autre.

     

Long-term response and recovery to nutrient addition of a partitioned arctic lake

1. To study the bottom‐up linkages in arctic lakes, we treated one side of a partitioned lake with inorganic nitrogen and phosphorus for a 6‐week period each summer for 6 years starting in the summer of 1985. We took a variety of weekly measurements to determine the impact of the nutrient loading on the lake and continued weekly measurements for 2–6 years after the cessation of nutrient loading to observe the recovery of the treated side. The loading rates (2.91 mmol N m^?2 day^?1 and 0.23 mmol P m^?2 day^?1) were five times the calculated loading rates for Toolik Lake, located nearby. 2. In all 6 years of nutrient addition, phytoplankton biomass and productivity were greater in the treated sector than the reference sector. In the first 4 years of nutrient addition there was no flux of phosphorus from the mineral‐rich sediments. This changed in the last 2 years of nutrient addition as phosphorus was released to the lake. 3. The response of the animal community to increased plant production was mixed. One of the four macro‐zooplankton species (Daphnia longiremis) increased in number by about twofold in the first 5 years. However, the copepod Cyclops scutifer showed no response during the treatment phase of the study. The benthic invertebrate response was also mixed. After a 2‐year lag time the snail Lymnaea elodes increased in the treated lake sector but chironomids did not. 4. Ecosystem response to fertilisation was not controlled solely by nutrient addition because phosphorus was not recycled from the sediments until the last 2 years of nutrient addition. Phytoplankton still showed the effects of nutrient addition in the recovery period and the hypolimnion of the treated sector was still anaerobic starting at 6 m in 1996.     

Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation

Size-related changes in hydraulic architecture, carbon allocation and gas exchange of Sclerolobium paniculatum (Leguminosae), a dominant tree species in Neotropical savannas of central Brazil (Cerrado), were investigated to assess their potential role in the dieback of tall individuals. Trees greater than ∼6-m-tall exhibited more branch damage, larger numbers of dead individuals, higher wood density, greater leaf mass per area, lower leaf area to sapwood area ratio (LA/SA), lower stomatal conductance and lower net CO₂ assimilation than small trees. Stem-specific hydraulic conductivity decreased, while leaf-specific hydraulic conductivity remained nearly constant, with increasing tree size because of lower LA/SA in larger trees. Leaves were substantially more vulnerable to embolism than stems. Large trees had lower maximum leaf hydraulic conductance ( K _leaf) than small trees and all tree sizes exhibited lower K _leaf at midday than at dawn. These size-related adjustments in hydraulic architecture and carbon allocation apparently incurred a large physiological cost: large trees received a lower return in carbon gain from their investment in stem and leaf biomass compared with small trees. Additionally, large trees may experience more severe water deficits in dry years due to lower capacity for buffering the effects of hydraulic path-length and soil water deficits.