Nachweis und Vorkommen von Actinomyceten in der österreichischen Donau mittels selektiver Membranfilterverfahren, zusammen mit einigen anderen bakteriologischen Parametern
[Detection and enumeration of actinomycetes in the Austrian part of the Danube by means of selective membrane filtration methods together with some other bacteriological parameters]
Kasimir, Georg D.
published: May 6, 1987
A method, by which substrate mycelia of actinomycetes in chitin agar are counted, proved to be superior to other methods for the enumeration of actinomycetes in surface waters in which they occur in relatively small numbers. The method uses the ability of actinomycetes to grow through membrane filters. As chitin, the sole source of nitrogen and carbon in this medium, is not water soluble, other bacteria growing on the upper side of the membrane filter are not able to use it and thus are restricted in their growth. Before counting, these bacteria are removed with the filter. The examination of Danube water samples showed a marked dependence of the actinomycete population density on the water level thus documenting their terrestrial origin. A similar behaviour is shown by the aerobic spore formers which are also wash-in forms. In contrast to the above groups of bacteria, bacteria which are of waste-water origin (saprophytes, faecal coliforms, faecal streptococci) show a more complex dependence on the water level: On the one hand, high water dilutes the waste-water inflow, but on the other hand the number of these bacteria, which may have a long survival time (Kavka 1978), is increased by the disturbance of the sediment in the case of high water. The bacteriological quality of the Danube water varies considerably depending on the hydrological changes. The importance of a high sampling frequency is therefore emphasized, especially when river systems are to be examined.