Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

Environment versus dispersal in the assembly of western Amazonian palm communities

Aim It is a central issue in ecology and biogeography to understand what governs community assembly and the maintenance of biodiversity in tropical rain forest ecosystems. A key question is the relative importance of environmental species sorting (niche assembly) and dispersal limitation (dispersal assembly), which we investigate using a large dataset from diverse palm communities. Location Lowland rain forest, western Amazon River Basin, Peru. Methods We inventoried palm communities, registering all palm individuals and recording environmental conditions in 149 transects of 5 m × 500 m. We used ordination, Mantel tests and indicator species analysis (ISA) to assess compositional patterns, species responses to geographical location and environmental factors. Mantel tests were used to assess the relative importance of geographical distance (as a proxy for dispersal limitation) and environmental differences as possible drivers of dissimilarity in palm species composition. We repeated the Mantel tests for subsets of species that differ in traits of likely importance for habitat specialization and dispersal (height and range size). Results We found a strong relationship between compositional dissimilarity and environmental distance and a weaker but also significant relationship between compositional dissimilarity and geographical distance. Consistent with expectations, relationships with environmental and geographical distance were stronger for understorey species than for canopy species. Geographical distance had a higher correlation with compositional dissimilarity for small‐ranged species compared with large‐ranged species, whereas the opposite was true for environmental distance. The main environmental correlates were inundation and soil nutrient levels. Main conclusions The assembly of palm communities in the western Amazon appears to be driven primarily by species sorting according to hydrology and soil, but with dispersal limitation also playing an important role. The importance of environmental characteristics and geographical distance varies depending on plant height and geographical range size in agreement with functional predictions, increasing our confidence in the inferred assembly mechanisms.     

Cardiovascular and respiratory responses associated with limb autotomy in the blue crab, Callinectes sapidus

Cardiovascular and respiratory variables were recorded in the blue crab, Callinectes sapidus, during injury and subsequent autotomy of a chela. Cardiac function and haemolymph flow rates were measured using a pulsed-Doppler flowmeter. Oxygen uptake was recorded using an intermittent flow respirometry system. Crabs reacted to the loss of a chela with a rapid increase in heart rate, which was sustained for 2 h. Stroke volume of the heart also increased after the chela was autotomized. A combined increase in heart rate and stroke volume led to an increase in cardiac output, which was maintained for an hour after the loss of a chela. There was also differential haemolymph perfusion of various structures. There was no change in perfusion of the anterolateral arteries or posterior and anterior aortae, during injury of the chela or subsequent autotomy. Haemolymph flow rates did increase significantly through the sternal artery during injury and immediately following autotomy of the chela. This was at the expense of blood flow to the digestive gland: a sustained decrease in haemolymph flow through the hepatic arteries occurred for 3 h following autotomy. Fine-scale cardiac changes associated with the act of autotomy included a bradycardia and/or associated cardiac pausing before the chela was shed, followed by a subsequent increase in cardiac parameters. Changes in the cardiovascular physiology were paralleled by an increase in oxygen uptake, which was driven by an increased ventilation of the branchial chambers. Although limb loss is a major event, it appears that only acute changes in physiology occur. These may benefit the individual, allowing rapid escape following autotomy with a subsequent return to normal activity.     

Aging-related changes in the sensitivity of the system of respiratory control and the intensity of free-radical processes in humans

Results of a comparative study of the sensitivity of the system of respiratory control to increases in the CO₂ concentration and the intensity of free-radical processes in young and elderly subjects are described. It is shown that normal (natural) aging is accompanied by a decrease in the sensitivity of the respiratory system to hypercapnic stimulation and a parallel significant decrease in the activity of catalase in the blood of examined subjects. Mechanisms responsible for the modifications of the sensitivity of the system of respiratory control to hypercapnia are discussed; these shifts can be at least partly related to changes in the intensity of production of free radicals observed in elderly subjects. Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 53–57, January–February, 2008.     

An automated technique for monitoring carbon dioxide respired by insects*

ABSTRACT. A non-dispersive infrared gas analyser equipped with a Luft-type sonic detector and flow-through reference cell was automated to monitor the total volume of carbon dioxide (CO₂) respired by single insects or groups of insects. The infrared analyser was interfaced with an integrator for quantification, a microprocessor to control intermittent air flow through the insect respiration chambers, and a microcomputer for data storage and reduction. This technique has been used to monitor the CO₂ Output of diapausing and non-diapausing mature fifth instar larvae and of developing pupae of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae). The resulting data were accurate, quantitative and reproducible.     

Survival of Escherichia coli in the environment: fundamental and public health aspects

In this review, our current understanding of the species Escherichia coli and its persistence in the open environment is examined. E. coli consists of six different subgroups, which are separable by genomic analyses. Strains within each subgroup occupy various ecological niches, and can be broadly characterized by either commensalistic or different pathogenic behaviour. In relevant cases, genomic islands can be pinpointed that underpin the behaviour. Thus, genomic islands of, on the one hand, broad environmental significance, and, on the other hand, virulence, are highlighted in the context of E. coli survival in its niches. A focus is further placed on experimental studies on the survival of the different types of E. coli in soil, manure and water. Overall, the data suggest that E. coli can persist, for varying periods of time, in such terrestrial and aquatic habitats. In particular, the considerable persistence of the pathogenic E. coli O157:H7 is of importance, as its acid tolerance may be expected to confer a fitness asset in the more acidic environments. In this context, the extent to which E. coli interacts with its human/animal host and the organism''s survivability in natural environments are compared. In addition, the effect of the diversity and community structure of the indigenous microbiota on the fate of invading E. coli populations in the open environment is discussed. Such a relationship is of importance to our knowledge of both public and environmental health.     

Resistance of Anhydrobiotic Aphelenchus avenae to Methyl Bromide Fumigation

The effect of methyl bromide (MB) was tested on active and anhydrobiotic Aphelenchus avenae. A. avenae was induced into anhydrobiosis by three different techniques. Both active and anhydrobiotic nematodes were subjected to 3,000 μ1 MB/liter air for 14 periods from 0 to 82 h. Anhydrobiotic nematodes were more resistant to fumigation than active nematodes, regardless of the technique used to induce anhydrobiosis. The percent survival decreased with increasing MB exposures (μ1 MB × h). For an LD₉₅ of 45,000-54,000 μ1/1 × h were required for active nematodes and >279,000 μ1/1 × h for anhydrobiotic nematodes.