Hiroshi Hirotani

Fluctuation of bacteriophage and Escherichia coli densities in naturally developed riverbed biofilms were investigated for a 1-year period. E. coli ranged from 1,500 to 15,500 most probable number (MPN)/100 mL and from 580 to 18,500 MPN/cm(2) in the main channel in the river water and biofilms, respectively. However, the fluctuations were much greater in the tributary, ranging from 0.8 to 100 MPN/100 mL and from 0.3 to 185 MPN/cm(2) in water and biofilms, respectively. The fluctuations of coliphages were also greater in the tributary than in the main channel. FRNA phage serotyping results indicated no significant differences in the source type of the fecal contamination in the main channel and tributary sampling stations. Significant correlations between phage groups in biofilms and water were found at both main channel and tributary. It was assumed that natural biofilms developed in the streambed captured and retained somatic phages in the biofilms for a certain period of time in the main channel site. At the location receiving constant and heavy contamination, the usage of phage indicators may provide additional information on the presence of viruses. In the small tributary it may be possible to estimate the virus concentration by monitoring the E. coli indicator.

Microbial indicators such as heterotrophic bacteria, total conforms, and Escherichia coli in naturally developed riverbed biofilms were investigated. Pebbles covered with natural biofilm were sampled directly from the riverbed at sampling stations ranging from the upstream region within a quasi-national park to the midstream in the urban district. Heterotrophic bacteria densities in biofilm positively correlated with stream discharge. E. coli densities in biofilm positively correlated with temperature, which suggests the growth in the biofilm. It was considered that the attachment of planktonic bacteria to biofilm was negligible. The biofilm may serve as an internal source of false positive indication of fecal contamination in the water column. © IWA Publishing 2010.

In the Ishite River, Japan, the stream water is completely diverted at head works except under flood conditions. The occurrence of Aeromonas hydrophila in channel above and below the head works in a mountain stream was studied monthly for twenty months. A. hydrophila and fecal coliforms were measured by the membrane filter methods. A. hydrophila was present throughout our study period, and was more abundant than fecal coliforms. The analysis of environmental factors in multiple regression revealed that the bacterial densities were positively affected by water temperature, flow velocity, and stream diversion. The impact of stream diversion was much greater than that of temperature rise, and therefore it is suggested that withdrawal of stream diversion can balance the water temperature rise caused by global warming, and thus can keep the risk of waterborne infection of A. hydrophila.

Water quality parameters in the water column of a dam reservoir were measured monthly in 2001. From July to November, the vertical profiles of alkaline phosphatase activity (APA) and related parameters were examined in detail. APA increased during the summer in epilimnion while it was almost stable in hypolimnion. A small increase in APA was observed at a depth immediately above the bottom of the lake. APA fluctuation was independent of soluble reactive phosphorus. It was assumed that APA is not indicative of the phosphorus status of aquatic microorganisms in the lake. A positive correlation was observed between chlorophyll a content and APA in the photic zone. In the aphotic zone, APA correlated positively with the colony count of heterotrophic bacteria, but not with microscopic total bacterial count.

Fluctuations of alkaline phosphatase activities in two streams and in reservoirs receiving the stream waters located in two adjacent but not connected watersheds were investigated from January to December in 2000. Alkaline phosphatase activities (APA) remained nearly constant in both streams, whereas in reservoirs they increased during the summer season. No relation was found between APA and soluble reactive phosphorus concentration. At one sampling station located in the stream, phosphorus concentration extraordinarily increased later in the study, but there were no related change observed in APA. An examination of size-fractionated samples suggested that most the APA in stream could be attributed to dissolved enzymes, whereas in reservoir most APA was related to bacterial particles. It assumed that APA is not indicative of phosphorus status of aquatic microorganisms.

The occurrence of Aeromonas hydrophila in a mountain stream was studied quarterly for more than 3 years. A. hydrophila and fecal coliforms were measured by the membrane filter method, and heterotrophic plate counts (HPC) were measured by the pour plate method at 20 and 35 degrees C. A. hydrophila was detected from all samples collected and correlated with HPC, especially at 35 degrees C, but not with fecal coliforms. A. hydrophila densities along the main stream in a log scale correlated positively with the catchment areas in a log scale. The intercepts of the regression lines correlated positively with the mean water temperatures along the channel, which is considered to reflect the growth of the bacterium on the stream bed. The slopes correlated negatively with total precipitation in a 60-day period before each sampling. These results suggested that the Factors controlling A. hydrophila in a mountain stream were water temperature and precipitation, and that the bacterium was indigenous to stream environment rather than from contamination because of human activity.

Dryobalanops aromatica and D. Ianceolata (hereafter denoted as Lin and Dl, respectively) are major Dipterocarp species constituting an emergent layer in the Bornean Rain Forest, and their distributions are in proximity, but never overlap. Thus, we examined the relationship between the distribution of these species and soils with reference to the soil physico-chemical, morphological, and microbiological properties, <BR>Based on the topographical investigation, was located only on the upper slope, whereas Dl occupied on both upper and lower slopes. The soil solums examined around these two species were always deeper than 1,3 meter. Soil texture was always sandy for the soils around Da, on the other hand, ranging from sandy te clayey for these around Dl. Furthermore, the following differences were found; 1) organic layer was thicker {n the Da soils, 2) soil color of subsurface horizons was duller in the Dl soils, and 3) only the Dl soils contained coarse fragments. 4) the amounts of exchangeable cations such as Ca and/or Mg and total oxides' content of K₂O, MgO, and P₂O₅ were higher for the Dl soils, 5) the amounts of exchangeable At and H were higher in the Da soils, 6} proportion of air phase and volume of macropore, and the value of sand content were higher for the Da soils, showing that the Da soils easily attain to drier soil moisture condition after rainfall, which was proved by monitoring soil water potential, 7) ten times as much fungal colonies were detected in the Da soils as compared to the Dl soils.<BR> These result$ suggest that Da emerges on a sandy soil with a dominance of drier soil moisture condition for some period and a low nutrient status with high acidity on the reflection of stable pedogenetic processes, while Dl stands on either clayey or sandy soil with a dominance of reductive condition for a certain period and relatively high nutrient status with low acidity, reflecting weak pedogenctic processes. It was well-known that shifting cultivators utilize a land where Dl dominates as a productive crop field, Their traditional way of land selection proves to be rational from the standpoint of soil science.

From a monthly survey over a ten-year period (1983-1992) of the Ishitegawa Reservoir, Japan, two multiple regression equations describing the mean chlorophyll a (Chl-a) concentration at 0.5 m depth during July, August and September (C-S) and the maximum Chl-a concentration in the photic zone, including its subsurface maximum during this period (C-M), were obtained. The conductivity at 0.5 m depth in May and the mean air temperature during May or during May and June were used as independent variables. These equations were calculated using seven years of data (1983-1988 and 1992). From 1989 to 1991 two impermeable plastic-coated sheet fences were installed across the upper end of the reservoir along the top 5 m of water column. The equations were used to determine the effectiveness of this flow regulation on the summer Chl-a concentration. In 1989 and 1991, when the fences were in place from June to August, no effects were found on the observed C-S and C-M values. In 1990, when the fences had been in place since October 1989, the observed values were lower than the predicted values.

Positive correlations in logarithmic scale were found between catchment areas and densities of bacteria in the upper reaches of the Ishite River in Ehime Prefecture, Japan. The constants, i.e. the intercepts and the slopes, given in the regression lines were analyzed to examine the factors affecting the bacterial counts. For this purpose we introduced the term "effective precipitation" which gives weight to the rainfall recorded near the day of sampling. It was suggested that total bacterial counts were affected by effective precipitation and water temperature. On the other hand, fecal coliform counts appeared to relate only to water temperature.

The antiviral extract from Rhodopseudomonas capsulata was purified and the predominant active component was defined as cis-vaccenic acid (Cl-8:1-DELTA-11) by gas-liquid chromatography and gas chromatography-mass spectrometry analyses. Antiviral activities of unsaturated fatty acids and related alcohols against T5 phage were also tested. Among them, linoelaidic acid, oleic acid, and petroselenyl alcohol inactivated 98%, 53%, 67% of T5 phage at the concentration of 50-mu-g/ml, respectively.

An antiviral substance produced by phototrophic bacteria was partially purified. The characteristics of this substance were as follows: 1) The substance inhibited the replication of Poliovirus type I at the concentration of 0.1μg/ml. 2) Antiviral activity of the substance was enhanced by Cu cation or ascorbic acid at a concentration of 1μg/m1 or 50μg/ml, respectively. 3) Antiviral activity of the substance was inhibited by Fe cation at a concentration of 10μg/ml. Studies for the detection of an antiviral substance similar to that produced by phototrophic bacteria were carried out in several fresh vegetables.

1) It was observed that the phototrophic bacteria, Rhodopseudomonas capsulata produce a substance that inactivates the Sindbis virus and the T_5 phage of E. coli. 2) The molecular weight of the antiviral substance was below 10,000 and the substance was neither a protein nor a high molecular nucleic acid. 3) The active subtance exhibiting the antiviral activity was found to be relatively stable upon heating (60℃) under dark condition. The activity of the antiviral substance increased when it was kept in contact with the virus under light condition. However when the extraction was performed in the light; the activity tended to decrease. Therefore, it is concluded that the antiviral substance should be extracted under dark condition as much as possible.