THE EFFECTS OF ULTRAVIOLET RADIATION ON SPORES OF THE FUNGUS ASPERGILLUS NIGER

The survival ratio of Aspergillus spores exposed to ultraviolet radiation has been measured as a function of total incident energy for wave lengths of 2537 Å, 3022 Å, 3129 Å, and 3650 Å. The effect of humidity on killing of Aspergillus spores by ultraviolet radiation has been found to be negligible. A delay in germination as a result of irradiation has been found. The Bunsen-Roscoe reciprocity law has been found to hold within the limits of the radiation intensities studied. Certain morphological changes have been observed.     

昆明水源水和自来水水质致突变性及化学背景值1．Ames试验和水源水及自来水微量有机、无机污染物化学背景值

本文报道：用ＸＡＤ－２离子树脂吸附富集法制备自来水和滇池及松华坝水库源水提取物,以Ａｍｅｓ鼠伤寒沙门氏菌回复突变系统诱发致突变性。Ａｍｅｓ试验结果如下：来自滇池源水经氯化的自来水提取物,用ＴＡ９８菌株加Ｓ９或不加Ｓ９混合物,突变率＞２,结果为阳性。滇池源水提取物致突变性为可疑。使用化学分析法结合生物分析法评价昆明自来水和滇池及松华坝水库水中的化学微量污染物,估价在水中的微量污染物对人体健康的潜在致癌效应是有意义的。     

INTRA- AND INTERSPECIFIC VARIATIONS IN CALCIUM CONTENT OF FRESHWATER MOLLUSCA IN RELATION TO CALCIUM CONTENT OF THE WATER

Analyses of calcium content of molluscs collected from 53 freshwaterhabitats on a naturally occurring calcium gradient between theCanadian Shield and limestone formations in southern Ontarioshowed both intraspecific and interspecific variations in relationto pH, total alkalinity, total hardness and calcium hardnessof the water. The calcium content of individuals is relatedto the calcium concentration of the water for only about halfof the species analysed. Two species (Sphaerium rhomboideumand Sphaerium simile) showed negative correlations, while six(Cincinnatia cincinnatiensis, Pisidium casertanum, Pisidiumcompressum, Sphaerium striatinum, Anodonta grandis grandis,and Elliptio complanata showed positive correlations beteencalcium content of individuals and environmental calcium content.In general, species associated with the sediments (e.g. bivalves)showed better calcium concentrations than did species associatedwith macrophytes (e.g. gastropods). (Received 12 July 1982;     

FURTHER OBSERVATIONS ON THE BACTERIAL CONTENT OF WATER IN WATERCRESS BEDS

SUMMARY: Observations on two watercress beds in Kent have confirmed previous findings (Jones & Baker, 1955) that even in comparatively well-protected beds the coli-aerogenes content of the water may be high in summer. They have also shown that in spite of circumstances which would lead one to expect pollution, as in the case of one bed, the coli-aerogenes content can be low in winter. The season appears to influence the content in the water of coli-aerogenes bacteria, pectate liquefying bacteria and those capable of growing at 37°, but in the case of those growing at 22° other factors can play a more important part, as higher counts were not uncommon in winter. Seasonal effects were less marked with inlet samples; they were less influenced by atmospheric temperature, and little extraneous contamination occurred. Numbers increased as the sampling point moved from inlet to outlet.     

PRIMARY AND SECONDARY EFFECTS OF WATER CONTENT ON THE SPECTRAL REFLECTANCE OF LEAVES

Leaves of six species selected to represent a broad range in internal structure were collected in the field and studied in the laboratory to determine primary and secondary effects of water content on leaf spectral reflectance. Primary effects were those that resulted solely from the radiative properties of water. Secondary effects were those that could not be explained solely by these properties. Decreased leaf water content generally increased reflectance throughout the 400-2,500-nm wavelength range. For the aquatics Eichhornia crassippes and Nuphar luteum, the broadleaved trees Liquidambar styraciflua and Magnolia grandiflora, the cane-grass Arundinaria tecta, and the needle-leaved Pinus taeda, the sensitivity of reflectance to water content was greatest in the water absorption bands near 1,450, 1,940, and 2,500 nm. Sensitivity maxima occurred also between 400 and 720 nm, indicating secondary effects that resulted from decreased absorption by pigments. Secondary effects of water content on reflectance that were largely wavelength-independent, together with any wavelength-independent effects of leaf internal structure, were far less significant than primary and secondary effects resulting from decreased absorption by water and pigments, respectively.     

A NOTE ON THE THERMODURIC BACTERIAL CONTENT OF FARM WATER SUPPLIES

SUMMARY: Significantly higher thermoduric colony counts were obtained when 5 ml. of water were laboratory pasteurized in 5 ml. of sterile milk or 2 ml. of water were pasteurized in 8 ml. of sterile milk, than when 10 ml. of water were directly pasteurized; 86% of the water samples had higher thermoduric counts after pasteurization in milk. Large differences were not common, only 19% of the ratios being over 5 and 5% over 10. Aerobic sporing rods were dominant in the thermoduric microflora irrespective of the method of pasteurization.     

SOME OBSERVATIONS ON THE BACTERIAL CONTENT OF WATER IN WATERCRESS BEDS

SUMMARY: Samples of water flowing into watercress beds had higher bacterial contents during the summer months although this was less marked among samples from deep underground sources. Outlet samples showed higher contents than inlet samples and the bacterial content varied markedly with season, being highest in summer.
The presumptive coli-aerogenes contents at 30°, 37° and 44° also showed a similar seasonal variation among samples from the outlets but the marked inferiority of samples other than from bores was no longer apparent after the water had flowed through the beds. The dominant types were Bact. aerogenes type I, pectate liquefiers, Bact. coli type I, and Intermediate type I.
The importance of the pectate liquefiers was confirmed by plating on pectate gel and by their isolation from these plates and from MacConkey's broth.     

STUDIES OF THE DETERMINATION OF THE BACTERIUM COLI TYPE I CONTENT OF FARM WATER SUPPLIES

SUMMARY: A – comparison of the suitability of brilliant green bile broth and MacConkey's broth at 44° for the detection of Bacterium coli type I in farm water supplies, showed that 83.1% of the samples had no difference in the number of positive tubes at 44°, and only 5 samples (1.7%) had a significantly higher number of positive tubes in MacConkey's broth.
Of 707 strains of coli-aerogenes bacteria isolated from 44° positive tubes of both media, 94.5% were Bact. coli type I. Strains of Bact. coli type II and Bact. aerogenes type I which were 44° positive constituted 3.7% and 0.4% respectively, all of which were indole negative at 44°. In addition there were 10 strains (1.4%) of 44° positive Intermediate type II, 9 of which were indole positive at 44°.
An appreciable number (6.6%) of Bact. coli type I strains failed to give a positive indole reaction in 24 hr at 44°.     

THE EFFECT OF WATER CONTENT UPON THE RATE OF HEAT DENATURATION OF CRYSTALLIZABLE EGG ALBUMIN

1. The denaturation rate of partially dried crystallizable egg albumin is greatly decreased by decreasing its water content. 2. The temperature of denaturation, defined as the temperature at which half of the protein becomes insoluble in distilled water after a definite time of heating, is a linear function of the relative humidity with which the protein is in equilibrium. 3. By applying the Arrhenius equation it is shown that the rate of heat denaturation at a given temperature is an exponential function of the relative humidity. 4. The application of the observed relations to the analysis of the mechanism of thermal death of microorganisms is suggested. 5. The water content of native and heat-denatured egg albumin is determined as a function of the relative humidity of water vapor. It is shown that the heat-denatured modification takes up approximately 80 per cent as much water at all relative humidities as does native egg albumin.     

VARIATION OF WATER CONTENT IN HELIX ASPERSA MULLER IN A NATURAL ENVIRONMENT

1. Daily and seasonal variations occur in the water content ofHelix aspersa Müller.
2. The water content is not constantthroughout 24 hours but fluctuatesby 2 to 10%. There is noapparent daily rhythm.
3. Humidity has an effect on the watercontent. Falls in relativehumidity to 60% or less, triggera decrease of the snails' hydration,over a range of temperatures,as well as a brief pause in activity.
4. Only external climaticconditions produce noticeable fluctuationsof water content,and they more particularly affect juvenileswhich undergo greaterevaporo-transpiration.
5. A seasonal rhythm in water contentexists in Helix aspersa,with maxima during spring and autumnand minima in June andJanuary.
6. The water content of juvenilesis always superior to that ofthe adults.
7. The water contentaffects the duration of the snail's activephase.

(Received 22 September 1988; accepted 5 February 1989)