The nutrient ion concentrations in the interstitial waters of biofilms (BFs) formed on reed and stone surfaces were investigated in the northern and southern basins of Lake Biwa over several years. The following were observed for both types of BF: 1) Concentrations of ammonium, nitrate, nitrite, and phosphate ions were much (hundreds to thousands of times) higher in the BFs than in the surrounding lake water; 2) the concentration of ions, especially nitrate ions, in the BFs changed seasonally, being higher from winter to spring and lower from summer to autumn, synchronizing with the changes in the lake water; 3) dissolved-form N:P ratios were higher in the lake water than BFs; and 4) the bacterial flora of the BFs differed from that of the lake water, with smaller seasonal variations. The present study reveals for the first time that the inside of BFs in a natural environment is rich in nutrient ions and shows similar seasonal changes as the lake water. The BFs in an aquatic environment provide a microenvironment capable of sustaining a specific bacterial flora different from that in the surrounding lake water.Key words: biofilm, nutrient ions, bacterial flora, Lake Biwa Microbial biofilms (BFs) are ubiquitous in aquatic environments and perform important environmental functions, including nutrient recycling (2, 5, 27) and purification of pollutants (8,14,15). Natural BFs are generally composed of a variety of microbes and their secretory products, such as extracellular polymeric substances (EPS). The EPS-containing matrix confers on the constituent microbes certain advantages over their free-living counterparts (16,17). An important advantage is the ability to trap and retain dissolved nutrients through an entrapment mechanism that has been proposed (4, 7, 11) and proven (9) to depend on ion exchange processes.However, few studies have been conducted on the nutrient conditions inside BFs formed in natural environments over a long period of observation. Therefore, the present study was designed to compare over several years the concentrations of various nutrient ions in the interstitial waters of BFs and the surrounding lake water. An additional aim was to examine the relationship between the nutrient conditions and bacterial flora inside the BFs. Moreover, the BFs formed on reed and stone surfaces were compared, to clarify the influences of the substratum surfaces.Here, we report for the first time that the nutrient conditions in a BF and in the surrounding water are significantly different with respect to concentrations of ions, particularly nitrate ions, while exhibiting similar seasonal variations. The relationships among the nutrient conditions, bacterial flora constitution, and the physicochemical properties of the BFs are discussed. Materials and Methods Study area and samplingLake Biwa is located in the central part of the Japanese Archipelago (Lat. 35°15' N, Long. 136°05' E). The lake has a surface area of 670 km 2 and a total storage volume of 2.75×10 10 m 3 , consisting of two basins that differ in wa...

The seasonal change of bacterial community structure in biofilms on the surface of reed (Phragmites australis) was investigated for about three years (from 2005 June to 2008 March) in Lake Biwa by comparing it with that in surrounding lake water. The community structure in biofilms was different from that in the lake water throughout the seasons and years. The community structure in lake water was similar in the same seasons of different years, corresponding to similar environmental factors (i.e., temperature, dissolved oxygen, and light intensity) and nutrient ion concentrations at the same season. However, the community structure in the biofilms was not similar in the same season of different years. This seems to be due to the formation of new biofilms on sprouted reeds in every early summer and the high nutrient concentrations and bacterial density in subsequently formed biofilms. Although the community structure in the biofilms changed along with the seasonal change, the bacteria belonging to Bacillus and Paenibacillus were detected in any season. This study revealed the possibility that the bacterial community structure in the initial stage of the biofilm formation govern the subsequent seasonal change of the community structure in biofilms.Key words: biofilm, bacterial community, seasonal change, Lake BiwaIn natural environments, microorganisms attach to surfaces and form biofilms. Biofilms are ubiquitous in aquatic environments and have been proposed and confirmed to have the ability to trap and retain ions, including nutrient ions (7,10,39).In Lake Biwa, where water temperature, dissolved oxygen (D.O.), and light intensity change seasonally with similar patterns every year, we have studied the biofilms on the surfaces of reeds and stones for about three years (from June 2005 to March 2008), and revealed that the interior of the biofilms is rich in nutrients, hundreds to thousands of times greater in nutrient ion concentrations, compared with the surrounding lake water. Furthermore, we have clarified for the first time that the nutrient ion concentrations in biofilms showed a similar seasonal change every year (high in winter and low in summer) synchronized with the change of lake water (39). We found that the extracellular polymeric substances (EPS) of biofilms have electric charges (17), and in a preliminary experiment, that biofilms accumulated the nutrient ions from surrounding water (unpublished data). The biofilms seem to accumulate the nutrient ions by the ion exchange process as proposed other study (10), and form a nutrient-rich environment showing similar seasonal change to the lake water. The higher nutrient ion concentrations in biofilms and the seasonal change of the concentrations may influence the microbial community structure and activity in the biofilms. To investigate microbial community structures in biofilms by considering the internal environment of biofilms will lead to the understanding of the ecology of natural biofilms.Several studies, although based on a short period (one year at...

There is limited information available about the physiological content of glyceraldehyde, a precursor of toxic advanced glycation end products. The conventional derivatization method for aldoses using 1-phenyl-3-methyl-5-pyrazolone did not allow reproducible quantification of glyceraldehyde due to the instability of glyceraldehyde compared to other aldoses. We optimized the derivatization condition to achieve high and reproducible recovery of derivatives for liquid chromatography tandem mass spectrometry quantification. Based on the stability of glyceraldehyde during sample preparation and high recovery of spiked standard, the present method provides reproducible quantification of glyceraldehyde in the body. The glyceraldehyde contents in fasting conditions in the rodent liver (mice: 50.0 ± 3.9 nmol/g; rats: 35.5 ± 4.9 nmol/g) were higher than those in plasma (9.4 ± 1.7 and 7.2 ± 1.2 nmol/mL). The liver glyceraldehyde levels significantly increased after food consumption (p < 0.05) but remained constant in the plasma. High fat diet feeding significantly increased plasma glyceraldehyde levels in mice (p < 0.005). In healthy human volunteers, the plasma glyceraldehyde levels remained unchanged after the consumption of steamed rice. In patients with type 2 diabetes, the plasma glyceraldehyde level was positively correlated with the plasma glucose level (r = 0.84; p < 0.0001).

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