Ability of fungi to degrade synthetic polymer nylon-6

Fifty-eight fungi have been tested for their ability to degrade a recalcitrant synthetic polymer polyamide-6, generally known as nylon-6. Most of them were isolated from a factory producing nylon-6. After preliminary screening, 12 strains were selected for submerged culture in a medium with nylon fibres as the only N-source. No degradation was observed with the isolates from the factory. Wood degrading fungi from a culture collection, however, degraded nylon after incubation for several weeks. Bjerkandera adusta disintegrated the fibres most efficiently, starting with the small transverse grooves, which deepened into cracks. The superficial layers crumbled to leave a thin inner core of the fibre, which finally broke down into fragments. The remaining insoluble part of the nylon showed a decrease in number average molecular mass from 16900 to 5600 during a 60-day incubation. Its thermal properties, such as shifts in melting points and broadening of the melting endotherms, were altered. The reduction of the amount of nylon and the composition of the liquid phase indicated that part of the polymer was degraded into soluble products. After 50 days, the total nitrogen content of the soluble fraction was 10-fold higher than in the control sample. Manganese peroxidase, presumably responsible for the degradation, was detected in the liquid phase. The study shows that only white rot fungi are able to break down nylon-6. For the first time this polymer was shown to be disrupted by B. adusta. The extent of the biodegradation indicates its potential for application in nylon waste reduction.     

Benzoic acid, a stimulant of odorant receptors of Bombyx mori, is rapidly metabolized to N-benzoylserine on the antennae

Summary. Benzoic acid is a known stimulant of olfactory receptor cells in trichoid sensilla on the antennae of adult females of Bombyx mori. Exposure of freshly excised antennae, from B. mori females and males, to vapours of [¹⁴C]-benzoic acid revealed that the adsorbed acid is rapidly metabolized (15% conversion in 10 s), suggesting the presence of a highly active enzymatic system. The major product could be identified as N-benzoylserine by use of [²H₅]-benzoic acid, and mass spectrometry linked to a gas chromatograph (GC-MS) or a liquid chromatograph (LC-MS), for analysis of the metabolites. The conjugation of benzoic acid with an amino acid apparently represents a novel mode for the rapid deactivation of odorant molecules. Received 26 March 2001.     

Molecular response of the sponge Suberites domuncula to bacterial infection

The aim of this study was the documentation of the molecular immune response of Suberites domuncula upon bacterial infection. Additionally, the bacteria that are naturally present in the sponge after prolonged aquarium maintenance were characterized. After 6 months of maintenance of S. domuncula in seawater aquaria, only one bacterial 16S rDNA sequence could be recovered, which belongs to the genus Pseudomonas. Concomitantly, morphologically uniform bacteria were found encapsulated in bacteriocytes. These findings indicate that certain bacteria, possibly of the genus Pseudomonas, are able to persist for long periods in host bacteriocytes. Subsequent to performing a previously established infection assay with S. domuncula, a potentially pathogenic Vibrio sp. was isolated from the tissues. Furthermore, the host tissue disintegrated and asexual propagation bodies (gemmules) were formed. In order to gain insights into the molecular events occurring after bacterial infection, the stress-response kinases, p38 protein kinase and JNK protein kinase, were analyzed. It is demonstrated that these two kinases are activated (phosphorylated) upon incubation of the tissue with the bacterial endotoxin lipopolysaccharide (LPS). Moreover, LPS strongly inhibits protein synthesis. It is concluded that there are many functionally different interactions between S. domuncula and bacteria and that the animal possesses mechanisms to differentiate between bacteria and to respond accordingly.     

Trends in land use and land cover change in the protected and communal areas of the Zambezi Region,Namibia

Land management decisions have extensively modified land use and land cover in the Zambezi Region. These decisions are influenced by land tenure classifications, legislation, and livelihoods. Land use and land cover change is an important indicator for quantifying the effectiveness of different land management strategies. However, there has been no evidence on whether protected or communal land tenure is more affected by land use and land cover changes in southern Africa and particularly Namibia. Our study attempted to fill this gap by analyzing the relationship between land use and land cover change and land tenure regimes stratified according to protected and communal area in the Zambezi Region. Multi-temporal Landsat TM and ETM+ imagery were used to determine the temporal dynamics of land use and land cover change from 1984 to 2010. The landscape showed distinctive modifications over the study period; broad trends include the increase in forest land after 1991. However, changes were not uniform across the study areas. Two landscape development stages were deduced: (1) 1984–1991 represented high deforestation and gradual increase in shrub land; (2) 1991–2000 and 2000–2010 represented lower deforestation and slower agropastoral expansion. The results further show clear patterns of the dynamics, magnitude, and direction of land use and land cover change by tenure regime. The study concluded that land tenure has a direct impact on land use and land cover, since it may restrict some activities carried out on the land in the Zambezi Region.     

Mechanisms of purple moor-grass (Molinia caerulea) encroachment in dry heathland ecosystems with chronic nitrogen inputs

We analysed growth strategies (biomass allocation, nutrient sequestration and allocation) of heather (Calluna vulgaris) and purple moor-grass (Molinia caerulea) seedlings in monocultures and mixtures in relation to N, P, and N + P fertilisation in a greenhouse experiment in order to simulate a heath’s pioneer phase under high airborne nitrogen (N) loads. N fertilisation increased the total biomass of both species in monocultures. In mixtures, M. caerulea sequestered about 65% of the N applied, while C. vulgaris suffered from N shortage (halving of the total biomass). Thus, in mixtures only M. caerulea will benefit from airborne N loads, and competition will become increasingly asymmetric with increasing N availability. Our results demonstrate that the heath’s pioneer phase is the crucial tipping point at which the competitive vigour of M. caerulea (high belowground allocation, efficient use of belowground resources, shortened reproductive cycles) induces a shift to dominance of grasses under increased N availability.     

Ultrafine particles at workplaces of a primary aluminium smelter

The number concentration and size distribution of ultrafine particles in a S?derberg and a prebake potroom of an aluminium primary smelter have been measured using a scanning mobility particle spectrometer. The particle morphology was studied by transmission electron microscopy (TEM). The study shows the existence of elevated number concentrations of ultrafine particles in both potrooms. The main source of these particles is likely to be the process of anode changing. The ultrafine particles were measured directly at the source but could also be identified as episodes of high number concentrations in the general background air. Unlike the larger particles belonging to the 50-100 nm mode, the nanoparticle mode could not be detected in the TEM indicating that they may not be stable under the applied sampling conditions and/or the high vacuum in the instrument.     

Forest ecosystems and the changing patterns of nitrogen input and acid deposition today and in the future based on a scenario

A global assessment of the impact of the anthropogenic perturbation of the nitrogen and sulfur cycles on forest ecosystems is carried out for both the present-day [1980-1990] and for a projection into the future [2040-2050] under a scenario of economic development which represents a medium path of development according to expert guess [IPCC IS92a]. Results show that forest soils will receive considerably increasing loads of nitrogen and acid deposition and that deposition patterns are likely to change. The regions which are most prone to depletion of soils buffering capacity and supercritical nitrogen deposition are identified in the subtropical and tropical regions of South America and Southeast Asia apart from the well known 'hotspots' North-Eastern America and Central Europe. The forest areas likely to meet these two risks are still a minor fraction of the global forest ecosystems, though. But the bias between eutrophication and acidification will become greater and an enhanced growth triggered by the fertilizing effects of increasing nitrogen input cannot be balanced by the forest soils nutrient pools. Results show increasing loads into forest ecosystems which are likely to account for 46% higher acid loads and 36% higher nitrogen loads in relation to the 1980-1990 situation. Global background deposition of up to 5 kg N ha-1 a-1 will be exceeded at more than 25% of global forest ecosystems and at more than 50% of forest ecosystems on acid sensitive soils. More than 33% of forest ecosystems on acid sensitive soils will receive acid loads which exceeds their buffering capacity. About 25% of forest areas with exceeded acid loads will receive critical nitrogen loads.     

Feeding ecology and energetics of the Antarctic chaetognaths Eukrohnia hamata, E. bathypelagica and E. bathyantarctica

Ecological and physiological studies focused on dietary preferences, lipid biochemistry and energetics within the three Antarctic chaetognaths Eukrohnia hamata, E. bathypelagica and E. bathyantarctica from meso- and bathypelagic depths. Eukrohnia hamata and E. bathypelagica respired 0.15 μL O₂ mg dry mass (DM)⁻¹ h⁻¹, which translates to an average metabolic loss of only <1.1% of body carbon per day. Lipid storage was not substantial in E. bathypelagica (mean 11.5 ± 6.5% DM) and E. bathyantarctica (mean 15.4 ± 4.1% DM) during summer and winter, suggesting year-round feeding of these predators mainly on copepods. In E. bathypelagica, total fatty acids were dominated by the fatty acids 16:0, 20:5(n-3) and 22:6(n-3) and in E. bathyantarctica also by 18:1(n-9), a fatty acid usually found in storage lipids. Only the latter species was characterized by significant amounts of wax esters, consisting largely of the common fatty alcohols 16:0, 20:1(n-9) and the unusual fatty alcohol isomer 22:1(n-9).