The composition of the microflora, N2‐fixing bacteria particularly, in different soils cultivated with wheat in Egypt was investigated in some samples collected from the fields after applying the agricultural practices recommended for wheat cultivation and just before sowing. The influence of carbon sources, mineral nitrogen and water regimes on potential dinitrogen fixation (acetylene reduction assay) in soils was investigated. The bacterial population densities including‐N2‐fixing organisms were related to a number of environmental factors such as organic matter content. Among diazotrophs, Azotobacter spp. and Azospirillum spp. were encountered in higher densities in comparison with clostridia. Unamended soils showed a lower acetylene‐reducing activity (0.5–61.5 nmoles C2H4 g−1 h−1). Addition of glucose (1% w/w) greatly enhanced such activity being the highest (86.9–2846.5 nmoles C2H4 g−1 h−1) in the clay soil with the highest organic carbon content (1.42%). Glucose amendment had no significant influence on acetylene reduction in the saline soil. N2‐fixation in barley straw‐amended (1%) soils was not much higher than in unamended soils. Concentrations of up to 70 ppm ammonium‐nitrogen depressed N2‐fixation in soils that received barley straw. Acetylene reduction in submerged soil increased after addition of cellulose. Non‐flooded conditions favoured N2‐fixation in the fertile clay soil amended with sucrose. Copyright © 1989 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim

Some fish species are suffering from continuous depletion due to devastating environmental changes at their native aquatic environment. Qarun Lake and Suez Gulf are among the most vulnerable areas. Thus, representative fish samples from those areas were inspected for the presence of any fish pathogenic bacteria. The inspected samples included six different species; Epinephelus tuvina, Siganus rivulatus, and Dedlechilus labiosus native to Suez Gulf at Suez governorate; Tilapia zilli, Mugil capito and Solea vulgaris native to Qarun Lake at El- Fayoum governorate. A total of 600 samples were examined throughout the different year seasons. Gram positive and negative fish pathogenic bacteria were isolated from a total of 245 fish sample. Among those samples, the following bacteria were retrieved in the following percentages respectively, 17.55% (V. anguillarum), 16.73% (V. alginolyticus), 15.51% (P. piscicida), 15.91% (Ps. fluorescens), 13.46% (S. fecalis), 11.02% (A. hydrophila), 6.12% (A. sobria) and 3.67% were infected with Staph. aureus. The Siganus rivulatus was the highest infected fish species with a prevalence of 8.33%, while Mugil capito was the lowest infected species (5.67 %). The highest total prevalence of bacterial infection was recorded in summer season (40.81%) while the lowest was recorded in winter (15.91%). The aforementioned bacterial isolates were successfully re-isolated from experimentally infected fish. The retrieved isolates were matched against standard isolates as well as confirmed to be positive using semi- automated (API 20 E) and conventional biochemical tests.

Some fish species are suffering from continuous depletion due to devastating environmental changes at their native aquatic environment. Qarun Lake and Suez Gulf are among the most vulnerable areas. Thus, representative fish samples from those areas were inspected for the presence of any fish pathogenic bacteria. The inspected samples included six different species; Epinephelus tuvina, Siganus rivulatus, and Dedlechilus labiosus native to Suez Gulf at Suez governorate; Tilapia zilli, Mugil capito and Solea vulgaris native to Qarun Lake at El- Fayoum governorate. A total of 600 samples were examined throughout the different year seasons. Gram positive and negative fish pathogenic bacteria were isolated from a total of 245 fish sample. Among those samples, the following bacteria were retrieved in the following percentages respectively, 17.55% (V. anguillarum), 16.73% (V. alginolyticus), 15.51% (P. piscicida), 15.91% (Ps. fluorescens), 13.46% (S. fecalis), 11.02% (A. hydrophila), 6.12% (A. sobria) and 3.67% were infected with Staph. aureus. The Siganus rivulatus was the highest infected fish species with a prevalence of 8.33%, while Mugil capito was the lowest infected species (5.67 %). The highest total prevalence of bacterial infection was recorded in summer season (40.81%) while the lowest was recorded in winter (15.91%). The aforementioned bacterial isolates were successfully re-isolated from experimentally infected fish. The retrieved isolates were matched against standard isolates as well as confirmed to be positive using semi- automated (API 20 E) and conventional biochemical tests.

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