Artikkelit jotka sisältää sanan 'Bacteria'

The aim of is study was to elucidate the bacterial quality of the River Nile water at Cairo region in Egypt. The microorganisms such as heterotrophic bacteria and faecal coliforms were examined. The bacterial isolates were identified using different keys of identification and Biolog metabolic fingerprint system. The results showed the presence of different genera of microorganisms, which were. Alcaligenes, Escherichia, Aeromonas, Pseudomonas, Klebsiella, Enterobacter, Rahnella, Xanthobacter, Streptomyces, Rhodococcus and Arthrobacter. The significance of the results was shortly discussed.

• Rifaat, Microbial Chemistry Department, National Research Centre, Cairo, Egypt Sähköposti: ei.tietoa@nn.oo

The gaseous plant hormone and air pollutant ethylene (C2H4) has a strong effect on plant physiological processes, such as ripening and senescence, and its removal is often required from contaminated air.This study tested the efficiency of indigenous microor ganisms in horticultural peat-soil to purify C2H4 contaminated air under biofilter condi tions.Peat-soil, acclimated to C2H4 removal, was placed in a biofilter (687 cm3) and subjected to an air flow (73 mL min–1 ) with ~117 ppm C2H4 (ppm, parts per million; equivalent to µL L–1 ).C2H4 was removed to a lowest level of 0.034 ppm after operation of the biofilter for 12 days at 26°C. This corresponded to a C2H4 removal efficiency of >99.9%and a specific C2H4 removal rate of 6.4 µg C2H4 g–1 dry wt soil h–1 (wt, weight). However, this efficient C2H4 removal was only transient (4 days), and during day 16 to 21, the C2H4 removal efficiency decreased to 51%. In contrast to this result, it was previously found that, under comparable biofilter conditions, cultivated ethylene-oxidizing bacteria were able to survive and efficiently remove C2H4 for at least 75 days. Thus, prolonged and efficient purification of highly C2H4 contaminated air by horticultural peat-soil under biofilter conditions apparently depended on bacterial inoculation.

• Elsgaard, Danish Institute of Agricultural Sciences, Department of Crop Physiology and Soil Science, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark Sähköposti: ei.tietoa@nn.oo

Two main factors control the rates of methane production in peat (in senso microbial formation of methane): the water table level and the chemical characteristics of the peat material. The water table restricts oxygen penetration into the peat because of the much slower diffusion of gases in water compared to gaseous phases. The oxygen distribution will govern the location of the strictly anaerobic, methanogenic bacteria in the peat profile. The degree of waterlogging will also influence the availability of the peat plant material for microbial decomposition, when it reaches the anaerobic zone. In waterlogged environments, the surface litter will quickly enter anoxic conditions. In such environments, high methane formation potentials are often found in the uppermost peat layers. Where the water table is positioned further down in the peat profile, a higher proportion of the easily degradable compounds are degraded under oxic conditions and therefore gone by the time the litter enters the anoxic layers. Lignified organic matter reaching the anaerobic zone will be little further degraded. This effect is most likely to be compounded if the nitrogen content of the litter is low. The net flux of methane from peat surfaces is highly dependent on the extent of microbial methane oxidation in the peat profile. Methane oxidizing bacteria need oxygen for the primary oxidation of methane and for their oxygen dependent respiration. The oxygen distribution, and hence the water table position, will therefore also affect the activity of the methanotrophic bacteria. Typically, highest methane oxidation activity is found around the most frequent position of the water table. At this level, high concentrations of methane meet oxygen diffusing down from the peat surface. Methane oxidation potentials in peat have been observed to correlate with the level of the water table, the concentration of methane just below this level, and in some sub-habitats, with the emissions of methane. Field studies have also shown that comparatively dry environments with fluctuating water table levels may act as sinks as well as sources for atmospheric methane. Some habitats show diurnal rhythms, with higher emissions during night. This is probably due to temperature limitation of the methanotrophic bacteria during the night. Keywords: Carbon flow, methanogenic bacteria, methanotrophic bacteria, mire ecology

• Svensson, Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, S-750 07 Uppsala, Sweden Sähköposti: ei.tietoa@nn.oo
• Sundh, Sähköposti: ei.tietoa@nn.oo