الفهرس 
General introductionOnly 14 pages are availabe for public view
 |  | from | 247 |  |  |
| | | from | 247 | | |
Abstract
The work in the present study began by collection of thirty soil lamples from different six localities representing Wadi Araba, Egypt. PVadi Araba is a big valley in the Eastern Desert of Egypt, and to our knowledge was not investigated microbiologically up till now.
The geomorphology, climatic factors and soil analysis of the study area were given. The climatic parameters recorded revealed that this area Is located in the hyperarid zone of Egypt with a mean annual temperature of 21.4°C and mean annual rainfall of 1 mm/year. The physicochemical [characteristics of the collected soil samples showed that all of them were bandy soils. The soil samples varied from slightly to moderate alkaline and also from non-saline to slightly saline.
We tend to isolate alkalophilic and alkaline-resistant microorganisms as a possible source of new antimicrobial compounds. Dilution plate technique was used for this purpose using Sato medium A recommended for isolating microorganisms on high alkaline medium. |The number of microbial colonies from the different soil samples varied from 102 to 104 CFU/g of soil. It was obvious that the viable microbial Runts were affected by the organic matter content and the pH of the soil.
A total of 117 alkalophilic and alkaline-resistant microorganisms ;were isolated. Among them, 73 isolates were bacteria, 40 isolates were fctinomycetes and the remaining 4 isolates were fungi. The purified alkalophilic and alkaline-resistant microorganisms were then investigated for their antimicrobial activities using the classical diffusion method. Certain Gram-positive & Gram-negative bacteria and fungi were used as ■est organisms for such a purpose. The alkalophilic actinomycetes were -Jie most active group and so we choose to continue work with them. The
diameter of inhibition zones of growth was used to select the working Isolate. The most potent isolate was the isolate WA52, which was ■elected for further studies. These included its identification to the species level; the effect of different environmental and nutritional factors on the biosynthesis of the active metabolite; and separation, purification and ■entification of the active compound.
The methods of characterization and identification of ■Sinomycetes were used for identification of the most potent alkalophilic Hfinomycete isolate WA52 under study. These methods included ■lalysis of the cells hydrolysate, morphological, physiological and Biochemical characteristics.
The analyses of cells hydrolysate of the alkalophilic actinomycete isolate WA52 under study showed that it contained meso- diaminopimelic pcid (maso-DAP) and no diagnostically sugars were detected. Due to that land other morphological characteristics, the most potent alkalophilic Bctinomycete isolate WA52 belongs to the genus Nocardiopsis.
Further identification of alkalophilic isolate WA52 under stud} were continued to the species level. For this purpose the available keys introduced in the Bergey’s Manual of Systematic Bacteriology and in the Bergey’s Manual of Determinative Bacteriology were used. B} [comparing the characteristics of alkalophilic isolate WA52 with th< [reference species of the genus Nocardiopsis, it matches wit! wfocardiopsis dassonvillei.
On the basis of differences in colors of substrate and aerial myceli; [and carbon sources utilization, the isolate WA52 under study may be ; inew subspecies and it was given the name Nocardiopsis dassonville IVA52.
A trail was made to optimize the conditions controlling th antimicrobial activity. Subsequently, the role played by various
od soluble in methanol, ethanol, acetone, ethyl acetate and chloroform; bartially soluble in water, ether and hexane; and insoluble in petroleum ether and benzene.
On the basis of the elemental analysis (C, 62.25; H, 9.3; N, 1.95 and O, 27.5) and mass spectra [(M-H)” = 716m/z] of the antibiotic WA52-■ under study, the molecular weight was calculated to be 717m/z and the molecular formula was deduced to be C^VHOTNOO.
The active compound exhibited positive reactions with Molish’s d Fehling reactions indicated the presence of a sugar moiety and free ehyde and/or ketone groups in its structure.
I Further studies including the spectroscopic characteristics (UV, IR, ss and NMR spectra) and the biological activities (minimum inhibitory Jcentration and the median lethal dose) of the purified antibiotic E52-A were also carried out. • The active compound under study is active against all the tested pram-positive bacteria and Klibsella penuminae NCIB 9111 from the -negative bacteria but no activity was detected against the tested Ip. It also exhibited low mammalian toxicity (LD50 = 230). I The antibiotic WA52-A under study was then subjected to an Btification process using the known keys of the antibiotics itification. It is one of the macrolide antibiotics particularly hromycins. This identity agrees with the chemical reactions, lecular formula and most physicochemical characteristics of the antibiotic WA52-A. Its identity to the erythromycin family is confirmed by the spectroscopic characteristics. To our knowledge, there was not any Nocardiopsis strain reported to be a producer of one of the fcrythromycins. So, the isolated alkalophilic isolate Nocardiopsis sonvillei WA52 was thus found to be a new producer of erythromycins.