The Distribution of Perkinsus marinus in Gulf Coast Oysters: Its Relationship with Temperature,Reproduction, and Pollutant Body Burden

Oysters from 48 Gulf of Mexico sites were examined for presence and infection intensity of the endoparasite, Perkinsus (= Dermocystidium) marinus (Mackin, Owen and Collier, 1950) as part of NOAA's Status and Trends Mussel Watch Program. Prevalence exceeded 75% at 25 sites. Infection intensity did not vary with sex or reproductive stage. Latitude, total polynuclear aromatic hydrocarbon (PAH) content and industrial and agricultural land use significantly affected the parasite's distribution. PAH and pesticide concentrations were latitudinally dependent, suggesting an impact of spawning frequency on uptake and depuration. P. marinus analysis complements the use of pollutant body burden for determining change in environmental quality because it responds differently than pollutant body burden to the biology and ecology of the oyster.     

Behavioural and chemical mechanisms behind a Mediterranean ant–ant association

1. Interspecific competition among ants is common, and so is competitive exclusion among dominant ant species. In contrast, specific associations between non‐parasitic ant species are rare, especially in the temperate zones. As an exception, the subordinate ant Camponotus lateralis frequently co‐occurs with the dominant Crematogaster scutellaris but rarely with other dominant ants. 2. This association is one of various associations between Camponotus and Crematogaster species across the world. However, the mechanisms behind these co‐occurences are largely unknown. 3. In the present study, we therefore investigated the association of Ca. lateralis and Cr. scutellaris. We studied the spatial association of the nests, interspecific aggression, both species' cuticular hydrocarbon profiles, and their propensity to follow the other species' pheromone trails. 4. Crematogaster scutellaris usually attacked and displaced the generally submissive Ca. lateralis, but was significantly less aggressive at jointly used trails. Camponotus nests were always in close proximity to Crematogaster nests. 5. The cuticular hydrocarbons of both species consisted of alkanes with chain lengths between C21 and C35. The two species had 25 hydrocarbons in common, including mono‐, di‐, and tetramethyl alkanes. Despite this qualitative similarity, however, the quantitative hydrocarbon composition differed between the two species. 6. Camponotus lateralis followed artificial trails containing trail pheromones of Cr. scutellaris, but the latter did not follow Ca. lateralis trail pheromones. Interspecific trail‐following by Camponotus, but not vice versa, has been observed in another Camponotus–Crematogaster association and may be a more general mechanism that facilitates associations between the two ant genera.     

Sexual dimorphism of arrestment and gregariousness in the bed bug (Cimex lectularius) in response to cuticular extracts from nymphal exuviae

Releaser pheromones have direct behavioural effects to arrest, attract or disperse insects, whereas interactions within groups of social insects are often influenced by primer pheromones. The behaviour of insects displaying intermediate levels of sociality is largely unexplored in this context. In the present study, both the gregariousness and arrestment (settling near the odour source) of bed bugs Cimex lectularius L. (Hemiptera: Cimicidae) in response to conspecific exuvial extracts are described. Adult males are arrested on filter papers with extracts derived from exuviae of fifth‐instar nymphs. Adult females and nymphs display no significant evidence for such behaviour. Adults of both sexes show no preference for extracts of male versus female fifth‐instar exuviae. Arrestment of adult males does not occur on papers treated with fourth‐instar exuvial extracts. Because the insects are assayed behaviourally in groups, an index is calculated describing how far bugs are away from being located independently of one another, as a measure of gregariousness. Adult males have lower values for this index (i.e. locations are closer to independence). Adult females, nymph cohorts and mixed age groups all have higher values for this index, which tend to increase over time. Females exhibit a clear increasing dose‐dependent relationship for this index. It is concluded that the extracts of fifth‐instar nymphal exuvia arrest males on refuges that possess the odour source. However, gregariousness is induced in females, without evidence of a tendency to assemble near the odour source.     

Extracellular oxidative enzyme production and PAH removal in soil by exploratory mycelium of white rot fungi

Selected strains of three species of white rot fungi, Pleurotus ostreatus, Phanerochaete chrysosporium and Trametes versicolor, were grown in sterilized soil from straw inocula. The respective colonization rates and mycelium density values decreased in the above mentioned order. Three- and four-ringed PAHs at 50 ppm inhibited growth of fungi in soil to some extent. The activities of fungal MnP and laccase (units per g dry weight of straw or soil), extracted with 50 mM succinate-lactate buffer (pH 4.5), were 5 to 20-fold higher in straw compared to soil. The enzyme activities per g dry soil in P. ostreatus and T. versicolor were similar, in contrast to P. chrysosporium, where they were extremely low. Compared to the aerated controls, P. ostreatus strains reduced the levels of anthracene, pyrene and phenanthrene by 81–87%, 84–93% and 41–64% within 2 months, respectively. During degradation of anthracene, all P. ostreatus strains accumulated anthraquinone. PAH removal rates in P. chrysosporium and T. versicolor soil cultures were much lower.     

Soil lipase activity – a useful indicator of oil biodegradation

The evaluation of soil lipase activity as a tool to monitor the decontamination of a freshly oil-polluted soil was tested in a laboratory study. An arable soil was experimentally contaminated with diesel oil at 5 mg hydrocarbons g^–1 soil dry weight and incubated with and without fertilization (N-P-K) for 116 days at 20°C. Lipase activity and counts of oil-degrading microorganisms were measured at regular time intervals, and the correlations with the levels of hydrocarbon concentrations in soil were investigated. The residual soil hydrocarbon concentration correlated significantly negatively with soil lipase activity and with the number of oil-degrading microorganisms, independent of fertilization. The induction of soil lipase activity is a valuable indicator of oil biodegradation in naturally attenuated (unfertilized) and bioremediated (fertilized) soils.     

Unconventional interactions between water and heterocyclic nitrogens in protein structures

We report an unusual interaction in which a water molecule approaches the heterocyclic nitrogen of tryptophan and histidine along an axis that is roughly perpendicular to the aromatic plane of the side chain. The interaction is distinct from the well-known conventional aromatic hydrogen-bond, and it occurs at roughly the same frequency in protein structures. Calculations indicate that the water-indole interaction is favorable energetically, and we find several cases in which such contacts are conserved among structural orthologs. The indole-water interaction links side chains and peptide backbone in turn regions, connects the side chains in beta-sheets, and bridges secondary elements from different domains. We suggest that the water-indole interaction can be indirectly responsible for the quenching of tryptophan fluorescence that is observed in the folding of homeodomains and, possibly, many other proteins. We also observe a similar interaction between water and the imidazole nitrogens of the histidine side chain. Taken together, these observations suggest that the unconventional water-indole and water-imidazole interactions provide a small but favorable contribution to protein structures.     

Identification of common structural features of binding sites in galactose-specific proteins

Galactose-binding proteins characterize an important subgroup of sugar-binding proteins that are involved in a variety of biological processes. Structural studies have shown that the Gal-specific proteins encompass a diverse range of primary and tertiary structures. The binding sites for galactose also seem to vary in different protein-galactose complexes. No common binding site features that are shared by the Gal-specific proteins to achieve ligand specificity are so far known. With the assumption that common recognition principles will exist for common substrate recognition, the present study was undertaken to identify and characterize any unique galactose-binding site signature by analyzing the three-dimensional (3D) structures of 18 protein-galactose complexes. These proteins belong to 7 nonhomologous families; thus, there is no sequence or structural similarity across the families. Within each family, the binding site residues and their relative distances were well conserved, but there were no similarities across families. A novel, yet simple, approach was adopted to characterize the binding site residues by representing their relative spatial dispositions in polar coordinates. A combination of the deduced geometrical features with the structural characteristics, such as solvent accessibility and secondary structure type, furnished a potential galactose-binding site signature. The signature was evaluated by incorporation into the program COTRAN to search for potential galactose-binding sites in proteins that share the same fold as the known galactose-binding proteins. COTRAN is able to detect galactose-binding sites with a very high specificity and sensitivity. The deduced galactose-binding site signature is strongly validated and can be used to search for galactose-binding sites in proteins. PROSITE-type signature sequences have also been inferred for galectin and C-type animal lectin-like fold families of Gal-binding proteins.     

Isolation and characterization of genes encoding polycyclic aromatic hydrocarbon dioxygenase from acenaphthene and acenaphthylene degrading Sphingomonas sp. strain A4

Sphingomonas sp. strain A4 is capable of utilizing acenaphthene and acenaphthylene as sole carbon and energy sources, but it is unable to grow on other polycyclic aromatic hydrocarbons (PAHs). The genes encoding terminal oxygenase components of ring-hydroxylating dioxygenase (arhA1 and arhA2) were isolated from this strain by means of the ability to oxidize indole to indigo of the Escherichia coli clone containing electron transport proteins from phenanthrene-degrading Sphingobium sp. strain P2. The translated products of arhA1 and arhA2 exhibited moderate sequence identity (less than 56%) to large and small subunits of dioxygenase of other ring-hydroxylating dioxygenases. Biotransformation with recombinant E. coli clone revealed the broad substrate specificity of this oxygenase toward several PAHs including acenaphthene, acenaphthylene, naphthalene, phenanthrene, anthracene and fluoranthene. Southern hybridization analysis revealed the presence of a putative arhA1 homologue on a locus different from that of the arhA1 gene. Insertion inactivation of the arhA1 gene in strain A4 suggested that the gene but not the putative homologue one was involved in the degradation of acenaphthene and acenaphthylene in this strain.     

Isolation and characterization of a novel sphingomonad capable of growth with chrysene as sole carbon and energy source

A bacterial strain able to grow in pure culture with chrysene as sole added carbon and energy source was isolated from PAH-contaminated soil after successive enrichment cultures in a biphasic growth medium. Initially, growth occurred in the form of a biofilm at the interface between the aqueous and non-aqueous liquid phases. However, after a certain time, a transition occurred in the enrichment cultures, with growth occurring in suspension and a concomitant increase in the rate of chrysene degradation. The strain responsible for chrysene degradation in these cultures, named Sphingomonas sp. CHY-1, was identified by 16S rDNA sequencing as a novel sphingomonad, the closest relative in the databases being Sphingomonas xenophaga BN6T (96% sequence identity). Both these strains clustered with members of the genera Sphingobium and Rhizomonas, but could not be categorically assigned to either genus. Sphingomonas sp. CHY-1 was characterized in terms of its growth on chrysene and other PAH, and the kinetics of chrysene degradation and 14C-chrysene mineralization were measured. At an initial chrysene concentration of 0.5 g l(-1) silicone oil, and an organic/aqueous phase ratio of 1:4, chrysene was 50% degraded after 5 days incubation and 97.5% degraded after 35 days. The protein content of cultures reached a maximum value of 11.5 microg ml(-1) aqueous phase, corresponding to 92 mg g(-1) chrysene. 14C-labelled chrysene was 50% mineralized after 6-8 weeks incubation, 10.7% of the radioactivity was incorporated into cell biomass and 8.4% was found in the aqueous culture supernatant. Sphingomonas sp. CHY-1 also grew on naphthalene, phenanthrene and anthracene, and naphthalene was the preferred substrate, with a doubling time of 6.9 h.     

Sesquiterpenes of the liverwort Scapania undulata

The essential oil of the liverwort Scapania undulata, collected in the Harz mountains, Northern Germany, was analysed by gas chromatography (GC), GC-mass spectrometry (MS) and several new components were isolated and investigated by various NMR techniques. As new natural compounds the sesquiterpene hydrocarbons (+)-helminthogermacrene (1) [the 4Z-isomer of germacrene A (9)], (-)-cis-beta-elemene (2) as a Cope-rearrangement product of 1, (+)-beta-isolongibornene (3) and (-)-perfora-1,7-diene (4) could be identified. 1 has an identical mass spectrum and identical GC retention time on a non-polar stationary phase as germacrene A (9) but is considerably more stable than the latter. The Cope-rearrangement of 1 proceeds slowly at 350 degrees C and (-)-cis-beta-elemene (2) is formed together with small amounts of other diastereoisomers.