Glucose control of staphylococcal enterotoxin A synthesis and location is mediated by cyclic AMP

The regulation of staphylococcal enterotoxin A (SEA) synthesis in a defined medium was studied using continuous culture techniques. SEA production was repressed by glucose and repression could be overcome by addition of exogenous cyclic AMP. As well as this classical catabolite repression control, addition of glucose to de-repressed steady-state cultures resulted in rapid disappearance of toxin from the medium (also mediated by loss of cyclic AMP). When the toxin dissappeared from the medium, it was taken up again by the bacteria without apparent modification.     

Hematological indices and oxidative stress biomarkers response to the starvation of Clarias gariepinus

Starvation effects for five weeks on energy reserves, oxidative stress and hematological indices in Nile catfish Clarias gariepinus was studied. The low protein level in starved fish may result from the lowering effect of prolonged starvation on protein synthesis rather than due to its degenerating protein. Moreover, the elevated level of serum amino acids may promote gluconeogenesis in liver. In addition, the lipid depletion in starved fish may be related to the preferential uses of lipids as an energy to starve fish. Also, unchanged glycemic level may introduce a potent evidence for the presence of active gluconeogenesis, depending on both amino and fatty acids precursors. Also, kidney and liver showed disturbances in metabolites associated with oxidative damage such as elevations in total peroxide, carbonyl protein and DNA fragmentation; these may cause dysfunction to these organs after five weeks of starvation. Total peroxide, carbonyl protein and DNA fragmentation were significantly increased in gills, liver and kidney by 29.9, 30.9 and 30.5; 83.6, 84.6 and 53.7; 82.4, 43.3 and 75.7%, respectively. Starvation induced severe anemia and loss of body weight in the fish. However, white muscle did not show any oxidative damage after five weeks of starvation.     

Integrated Use of Organic and Bio-fertilizers to Improve Yield and Fruit Quality of Olives Grown in Low Fertility Sandy Soil in an Arid Environment

Olive productivity should be improved through stimulating nutrition, particularly under poor fertility soils. Consequently, the objective of this study was to assess the efficacy of applying organic and bio-fertilizers on the physiological growth, yield and fruit quality of olive trees under newly reclaimed poor-fertility sandy soil in an arid environment. During a field experiment carried out at El-Qantara, North Sinai, Egypt over two consecutive seasons (2019–2020 and 2020–2021), olive Kalamata trees were evaluated under three organic fertilizer treatments alone or in combination with three bio-fertilizers treatments. Organic fertilizer was applied as goat manure (16.8 kg/tree/year), or olive pomace (8.5 kg/tree/year) in mid-December of each season vs. untreated trees. The bio-fertilizers were applied as N-fixing bacteria (150 g/tree) was inculated in early March of each season, or amino acid mixture (1.5%) was applied three times, at 70% of full bloom, 21 days after full bloom, and a month later in comparison to a non-fertilized trees (control). The cultivar used was Kalamata, a dual-purpose cultivar for oil and table olives whose value increases when processed as table olives. The results indicated that the goat manure followed by olive pomace significantly enhanced photosynthetic pigments (chlorophyll a, b, and carotenoids), leaf mineral contents (N, P, K, Ca, Mg and Fe), tree canopy volume, number of flowers per inflorescence, number of inflorescences per shoot, initial fruit set, fruit retention. For fruit quality, fruit length and width, fruit weight, and total fruit yield was increased compared to the non-fertilized control. Likewise, The bio-fertilizer N-fixing bacteria followed by the amino acid mixture significantly improved all of the aforementioned parameters. Accordingly, it is recommended, both environmentally and economically to utilize organic and bio-fertizers, particularly goat manure combined with N-fixing bacteria, in low-fertility soil to sustain olive production as well as reducing mineral fertilization.