Prodigiosin is a natural red pigment, it is an alkaloid secondary metabolite with a unique tripyrrole structure produced by Serratia marcescens, it's motile, short-rod shaped, Gbacteria, classified in the large family of Enterobacteriaceae. 13 isolates were isolated from 32 soil samples, which showed clear red pigmented colonies. The Egyptian Serratia marcescens isolates were identified based on morphological, biochemical and then only the two best isolates for pigment production (M1, S1) were identified by MALDI-TOF mass spectrometry technique. The two selected species gave a score value between 2.565 to 2.668 (100%) were correctly identified by MALDI-TOF-MS to the genus and species levels. The average daily rate of pigment production by M1 and S1 isolates estimated by 421.6 and 326.1 unit/cell, respectively. Antibacterial activity of prodigiosin was determined by disc diffusion assay against 7 types of Gand 4 types of G + pathogenic bacteria. Minimum inhibitory concentration (MIC) and the concentration inducing 50% inhibition of the bacterial growth (IC 50) against the mentioned bacteria were determined and prodigiosin was proved to be effective in inhibiting bacterial growth. Prodigiosin possess antioxidant activity assayed by 2,2diphenyl-1-picrylhydrazyl (DPPH) reduction method and this activity increased gradually with increasing concentrations.
A total of 20 isolates of lactic acid bacteria (LAB) were isolated anaerobically from different food sources (Domiati cheese; raw milk and mixed pickles). Three out of 20 isolates showed high inhibition of growth pathogenic bacteria by well diffusion assay method and therefore they were chosen for bacteriocin production and further studies. The selected isolates were identified based on morphological, biochemical and MALDI-TOF mass spectrometry. All of the tested species gave a score value between 2.116 to 2.165 (100%) were correctly identified by MALDI-TOF-MS to the genus and species levels. They were identified as L. brevis, L. plantarum and L. fermentum. The bacteriocin was purified by salt precipitation and gel chromatography methods. The molecular weight was determined by SDS-PAGE and amino acid composition was also analysed. The purified bacteriocin was characterized and found to be thermostable at temperatures up to 90°C for 30min, pH from 3 to 11 and its activity improved in the presence of Tween 80, SDS and EDTA. The contents of bacteriocin from the acidic amino acid residues aspartic + glutamic (asp+glu) were 0.74% for all tested samples. The contents of the basic amino acids argnine + lysine + hisitidine (arg + lys + his) were 0.23% for all the tested samples.
Forty-two cyanoprokaryota strains were isolated from 10 diverse sites along Sharkia Governorate, Egypt (7 sites representing the fertile soils and 3 sites representing the new reclaimed soils). Eight genera and 11 species of N 2 -fixing cyanoprokaryota were identified based on available morphological distinction and physiological characterization. On the basis of the obtained results, we classified these isolates to 3 genera and 5 species isolated from fertile soils and 7 genera and 8 species isolated from new reclaimed soils. Nostoc spp strains were the most common filamentous heterocyst-forming cyanoprokaryota (22 strains) and two species of Nostoc including 11 strains of N. muscorum and 11 strains of N. calicicola. Anabaena includes 10 strains in three species (A. oryzae (6 strains), A. circinalis (2 strains) and A. oscillarioides (2 strains). Nodularia spumigena were represented in this work by two strains from fertile soils. In addition Calothrix clavata (2 strains), Synechococcus sp. (3 strains) and one strain of each Oscillatoria homogenea, Dermocarpa olivacea and Xenococcus kerneri were inhabited in the reclaimed soils. This indicates that Nostoc spp. and Anabaena spp. were highly distributed in fertile soils more than new reclaimed soils. The latter species were the most important cyanoprokaryota genera to fix atmospheric nitrogen in rice field.
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