biologia - Studia

MICROBIOLOGICAL AND ENZYMOLOGICAL STUDY ON RIVER SEDIMENTS AND WATER
also aimed to appreciate the level of the enzymatic activity in sediments of the same
river, at the same 5 sampling sites situated upstream the Gilău treatment plant.
Materials and methods
The microbiological analyses pursued the presence of coliform germs in water
of the Someş river before it reached the treatment plant in Gilău. The analyses were
carried out seasonally, in 2007, on water sampled from five sites, as follows:
P1 – Someşul Cald, 300 m upstream the filtration station Gilău;
P2 – Someşul Rece, 500 m upstream the filtration station Gilău;
P3 – the confluence of the rivers Someşul Cald and Someşul Rece;
P4 – left side of the Gilau dam reservoir;
P5 – right side of the Gilau dam reservoir.
We determined the total and faecal (thermotolerants) coliform bacteria,
according to the STAS 3001-91. In order to differentiate the genera of coliforms,
seven biochemical tests have been carried out on the water sampled in autumn, at the
P2 site, where the highest number of coliforms had been registered: indole production,
methyl red test, Voges-Proskauer test, citrate utilization (the four IMViC tests),
malate utilization, urea hydrolysis on Christensen medium and H 2 S production on
TSI medium (Drăgan-Bularda, 2000, Atlas, 2004, Garrity, 2005).
We also analysed the enzymatic potential of sediments at the same five
sampling sites in autumn. The following three enzymatic activities were studied:
phosphatase (Krámer and Erdei, 1959), catalase (Kappen, 1913) and potential
dehydrogenase (Casida et al., 1964).
Results and Discussion
Fig. 1 presents the seasonal variation of the number of total coliform germs in
the 5 sampling sites. High values of the number of total coliform germs (calculated
by McCrady matrix) have been noticed in most of the cases. The number of total
coliform germs was lower in winter and sometimes in spring, and higher in
summer and autumn. The highest value (35000 germs/l) was registered in P2, in
autumn, and the lowest one (54 germs/l) in P1, in winter.
A similar situation can be noticed in the case of the faecal coliforms (fig. 2).
The number of faecal coliforms was lower, generally by an order of magnitude as
compared to the total coliforms. The higest value (6400 germs/l) was also registered in
autumn in P2. A positive correlation (r = +0,983) with a good statistical significance
(p