Composition changes in the cuticular surface lipids of the helophytes Phragmites australis and Juncus effusus as result of pollutant exposure.

AIM OF THE STUDY: Helophytes like rush and reed are increasingly used for phytoremediation of contaminated water. This study characterises the response of rush and reed plants to chemical stressors such as chlorobenzene, benzene and methyl-tert-butyl ether. The extractable wax layer of the cuticle was chosen for detailed investigations due to its multiple, particularly, protective functions for plants and its easy availability for analysis. METHODS: The chemical composition of the cuticle wax layer of reed and rush was studied in dependence on chemical stress caused by contaminated water under wetland cultivation conditions. The lipid layer of leaves was extracted, derivatised and investigated by GC-MS using retention time locking and a plant-specific data base. RESULTS: In case of rush, a remarkable increase of the total lipid layer and a prolongation of the mean chain length resulted as response on a chlorobenzene exposure. The significant difference in the substance profiles of exposed plants and controls could be confirmed by multivariate data analysis. The lipid layer of reed was not changed significantly when the plants were exposed to water polluted with benzene and methyl-tert-butyl ether. However, scanning electron microscopic images of the exposed reed leaves indicated alterations in the crystal structure of their wax surface. CONCLUSION: The composition and morphology of cuticular waxes indicated the plants' response to chemical stress very sensitively thus, changes in the wax layer could be used as an indication for growing in a contaminated area.

Reclassification of Clostridium hydroxybenzoicum as Sedimentibacter hydroxybenzoicus gen. nov., comb. nov., and description of Sedimentibacter saalensis sp. nov..

Strain ZF2T, isolated from freshwater sediment, is a motile, rod-shaped, gram-positive, endospore-forming, amino acid- and pyruvate-utilizing, anaerobic bacterium. It requires yeast extract for growth. Carbohydrates are not utilized. The optimal temperature and pH for growth are 37 degrees C and 6.8-7.3, respectively. The G+C content of the DNA is 34.0 mol %. A 16S rDNA sequence analysis of strain ZF2T revealed that the highest similarity (94.4%) was shared with Clostridium hydroxybenzoicum JW/Z-1T. Strain ZF2T, however, was not able to carboxylate phenol or to decarboxylate 4-hydroxybenzoate, which are characteristic properties of strain JW/Z-1T. The degree of 16S rDNA relatedness, together with the physiological and chemotaxonomic properties, suggest that strain ZF2T represents a novel species that is clearly distinct from Clostridium hydroxybenzoicum JW/Z-1T. In a phylogenetic dendrogram, both strains form a separate cluster that is peripherally associated with the Peptostreptococcus group (cluster XIII) of the clostridia and the lineage of Helcococcus kunzii. Strains ZF2T and JW/Z-1T show a somewhat deeper branching from the cluster XII clostridia Clostridium purinolyticum and Clostridium acidiurici. The latter strains possessed the closest 16S rDNA similarity (between 88.4 and 90.7%), but were clearly separated by phenotypic markers. Therefore, a new genus, Sedimentibacter gen. nov., is described, comprising Sedimentibacter hydroxybenzoicus gen. nov., comb. nov., as the type species of the genus, with JW/Z-1T (= ATCC 51151T = DSM 7310T) as the type strain, and the novel species Sedimentibacter saalensis sp. nov., with strain ZF2T (= DSM 13558T = ATCC BAA-283T) as the type strain.