Mn accumulation in a submerged plant Egeria densa (Hydrocharitaceae) is mediated by epiphytic bacteria.

Many aquatic plants act as biosorbents, removing and recovering metals from the environment. To assess the biosorbent activity of Egeria densa, a submerged freshwater macrophyte, plants were collected monthly from a circular drainage area in Lake Biwa basin and the Mn concentrations of the plants were analysed. Mn concentrations in these plants were generally above those of terrestrial hyperaccumulators, and were markedly higher in spring and summer than in autumn. Mn concentrations were much lower in plants incubated in hydroponic medium at various pH levels with and without Mn supplementation than in field-collected plants. The precipitation of Mn oxides on the leaves was determined by variable pressure scanning electron microscopy-energy dispersive X-ray analysis and Leucoberbelin blue staining. Several strains of epiphytic bacteria were isolated from the field-collected E. densa plants, with many of these strains, including those of the genera Acidovorax, Comamonas, Pseudomonas and Rhizobium, found to have Mn-oxidizing activity. High Mn concentrations in E. densa were mediated by the production of biogenic Mn oxide in biofilms on leaf surfaces. These findings provide new insights into plant epidermal bacterial flora that affect metal accumulation in plants and suggest that these aquatic plants may have use in Mn phytomining.

Effects of repeated short-term skin contact with proteolytic enzymes.

The objective was to investigate effects on the hand of protease used in dishwashing liquids (DWL). A group of 30 Koreans (normal skin) and 24 Japanese (12 atopic and 12 normal) were employed for two different studies, respectively. The 30 Koreans were divided into three groups. Each group immersed their hands for 15 min a day for 9 days into DWL containing 0.005% protease, 0.02% protease, or non-enzyme DWL. The 24 Japanese immersed their hands for 15 min a day for 4 days into 0.005% protease-containing or a non-enzyme DWL. The hand skin was evaluated by measuring overall and dry skin grades, estimated before and after exposures to the test products. The Korean study shows that 0.005% and 0.02% protease-containing DWL are less irritating to the skin than non-enzyme control, as measured by better overall skin grades and less dry skin. The Japanese study shows that 0.005% protease-containing DWL are less irritating to the skin than non-enzyme control in both atopic and normal subjects. The 0.005% protease use did not cause any adverse dermatological effects to atopic subjects compared with non-enzyme control. Both studies indicate that 0.005% and 0.02% protease resulted in better skin mildness profile, without causing adverse dermatological complications to the subjects.