Sixteen identified and three unidentified species belonging to six genera of zoosporic fungi were isolated from forty water samples which were collected from different fish and fish hatcheries farms at Abbassa city, Sharkiya governorate, Egypt, using sesame seeds baiting technique at 20±2°C. Saprolegnia and Achlya contributed the broadest spectra of species diversity amongst the other genera of zoosporic fungi. Saprolegnia diclina and Aphanomyces sp. were the most prevalent species of zoosporic fungi. The abundance of zoosporic fungal species in these aquacultures was correlated with some physicochemical characteristics of the water samples. The two dominant species of zoosporic fungi were tested for their tolerance of NaCl solution and its impact on some morphological and metabolic activities of these fungi. Saprolegnia diclina tolerated concentrations of NaCl solution till 12000 μg/ml whereas the maximum resistance of Aphanomyces sp. was 8000 μg/ml. The examined morphological aspects of the two studied fungal species, which included the colony diameters, the vegetative hyphae, zoosporogenesis, zoospores discharge, sexual reproductive structures and gemmae formation, were generally affected depending upon the tested fungal species and the applied dose of NaCl solution. The low treatments of NaCl solution were significantly stimulative compared with the control for protease production by S. diclina but higher doses were significantly suppressive. A significant decline in protease activity at all applications was found when Aphanomyces sp. was treated with NaCl solution. The total free amino acids and total protein content of S. diclina and Aphanomyces sp. mycelia were almost significantly increased relative to untreated controls at the low dose of NaCl solution and they were significantly dropped at the higher concentrations by the two zoosporic fungi.
The paper gives a comprehensive insight into the role of zinc in the biosphere. It reviews numerous functions of this metal at various levels of the organisation of ecosystems. An attempt has ben made to assess its importance as a microelement, while not neglecting its toxicity due to excessive accumulation of zinc in the environment. Zinc is a natural component of the Earth's crust, but in many places it has accumulated in amounts near or above the safe levels. Currently, the use of this metal is very broad, and therefore attention should be drawn to possible consequences arising from elevated levels of zinc in the environment. Dispelling controversies surrounding heavy metals is a necessary step for gaining systematic and wider knowledge on these elements. This in turn will create an opportunity for the development of strategies and subsequent actions undertaken by everyone, from individuals to major international industrial corporations, aimed at achieving homeostasis in an environment polluted with heavy metals. Increased levels of zinc can adversely affect microbiological and biochemical processes occurring in the soil and the development of plants, which has a negative impact on the quantity and quality of crops. Therefore, low bioavailability of heavy metals, including zinc, in agricultural land is a key to the stability of ecosystems and food security.
The influence of crumbled sewage sludge on the biological properties of podzolic soil was studied under laboratory conditions during a five-month period. It was found that when compared to only slightly crumbled sludge, soil mixed with two different concentrations of crumbled sludge (1% and 10%) of a 0.5-mm particle diameter exhibited an increase in the numbers of all tested bacteria groups (total, lipolytic, cellulolytic, proteolytic). The stimulation of development of some fungi groups (cellulolytic, proteolytic) was also observed in soil with higher contents of crumbled sludge. Finally, strongly crumbled sludge stimulated most of the biochemical activities of the soil (ammonification, nitrification, dehydrogenases, lipase, protease). Such an effect was most evident in the cases of dehydrogenases and protease.
The effect of soil contamination with copper on soil biochemical properties and oat yields was assessed in a pot experiment. Copper was applied alone or in combination with other heavy metals. The study was conducted on samples of brown soil consisting of heavy loamy sand and brown soil developed from light silty clay. On days 28 and 56 of the experiment the following were determined: activity of dehydrogenases, urease, acid phosphatase and alkaline phosphatase in soil as well as oat yields. Contamination of soil with copper, zinc, nickel, lead, cadmium and chromium in concentrations of 50 mg kg-1 was found to have a negative influence on the activity of dehydrogenases, urease, acid phospha- tase, alkaline phosphatase and yield of oats. The soil enzymes can be arranged in terms of their sensitivity to heavy metals as follows: dehydrogenases > urease > alkaline phosphatase > acid phosphatase. Higher activity of dehydrogenases was determined in brown soil developed from heavy loamy sand, while urease, acid phosphatase and alkaline phosphatase were more active in brown soil formed from light silty clay. The contamination of copper with other heavy metals was inhibited in heavy loamy sand more than in light silty clay.
Emission of light as a result of biochemical activities of some living bacteria Vibrio fischeri (in the past known as Photobacterium phosphoreum) makes it possible to monitor environmental changes in ecosystems. Toxicity testing as an international standard operating procedure based on the use of this method has already been accepted. The bioluminescent test offers a rapid, simple and sensitive method to test a wide spectrum of chemical substances and environmental samples including water, wastewater, sludge extracts, etc. In this study, aimed at characterising and comparing bioluminescent properties, four different bacterial strains were cultivated in four different liquid mediums and temperature conditions. The bioluminescent intensity of bacterial suspensions was measured using a laboratory BioOrbit 1253 luminometer during bacteria culture. Based on obtained results and mathematical calculations of RLU (relative luminescent units) values strain Photobacterium phosphoreum + NCBE medium were indicated as the variant demonstrating proper bioluminescence intensity and characteristics most suitable for further applications.
Our study was conducted on a podzolic soil from a field experiment in which, 9 years earlier, municipal- industrial sewage sludge was introduced at doses of 30, 75, 150, 300, and 600 Mg·ha-1. Following the application of the sludge, the soil was planted with basket willow (Salix viminalis L.). Soil samples for the analyses were taken twice (at the beginning and at the end of the vegetation season of the 9th year) from depths of 0-20 cm and 20-40 cm. The soil material was used for determinations of the total numbers of bacteria with low and high nutrition requirements, the numbers of filamentous fungi, proteolytic bacteria and fungi, respiratory activity, rate of cellulose mineralization, rate of ammonification and nitrification, and of dehydrogenase and protease activity. The results obtained demonstrated that in the 9th year from the application of the sludge there was continued effect of its application on most of the microbiological properties (exception – proteolytic bacteria) and on all of the biochemical parameters. There was notable stimulation of the growth of cellulolytic bacteria and of the fungal groups under analysis. Increased activity was also displayed by almost all biochemical parameters, with the exception of ammonification (in both layers of the soil) and nitrification (in the deeper horizon of the soil), in which case significant inhibition was observed.
W wyniku przeprowadzonych badań właściwości chemicznych i biochemicznych gleby spod niekontrolowanego wysypiska w gminie Banie stwierdzono, że posiadała ona większą żyzność niż gleba ze znajdującego się nieopodal nieużytku rolnego. Jednak wykazano także, iż charakteryzowała się ona znaczącą fitotoksycznością, zwłaszcza dla roślin dwuliściennych.