BIOCHEMICAL AND MOLECULAR CHARACTERIZATION OF AN AZOTOBACTER-VINELANDII STRAIN WITH RESPECT TO ITS ABILITY TO GROW AND FIX NITROGEN IN OLIVE MILL WASTE-WATER

The bacterial strain A belongs to a collection of nitrogen fixing bact eria isolated from soil treated with olive mill wastewater (OMW). This strain can grow in OMW showing significant nitrogen fixing capacity. The study of growth and nitrogenase activity of the above strain durin g its growth into the waste showed that the maximum value of total ace tylene reduction activity (expressed in nmol Ethyl/24h/ml of culture) was obtained after 24h of incubation as well as the maximum value of b acterial population. When the above nitrogen fixing capacity was expre ssed in reference to the bacterial population (nmol Ethyl/24h/mu g bac terial protein) its maximum value was observed earlier, since the firs t 7h of incubation. Western blot analysis of total bacterial proteins, extracted at specific time intervals showed that nitrogenase activity was induced 30 mins after the inoculation of the waste with the strai n A, The respective time of the enzyme's induction in chemical media ( N-free) was Ih. Southern blot analysis of total genomic DNA of strain A using as probes the three structural genes (nifH, nifD, nifK) encodi ng nitrogenase-l in Azotobacter vinelandii gave hybridization patterns which are conserved between the above two bacteria. These results str ongly support parallel biochemical taxonomy data indicating that strai n A may belong to Azotobacter vinelandii species. (C) 1997 Published b y Elsevier Science Limited.