Identification and study of cultural conditions affecting Neomycin antibiotic produced by Streptomyces sp. N

: Cuftural conditions affecting antibiotic production by local isolate of Streptomyces sp. N were studied. Cultural conditions included groMh medium, growth temperature,pH, and ion effect. The study showed that this local isolate was able to produce neomycin antibiotic. This compound showed a biological activity against gram - positive, and gram - negative bacteria. This effect was variable depending on the factors studied. Media of antibiotic production, R2 medium, and complete medium rvere better for Slreptomyces growth. Growth of the organism for 5 days gave the largest inhibition zones against test bacteria. The organism shorved better gror,l,th and antibiotic production when cultivated at 370C. The pH of the medium showed a dramatic effect on antibiotic production since low pH had increased antibiotic release to the medium resulting in observed increased in the biological activity. Ions like phosplrate and citrate shorved diff'erenteff'ecton the antibiotic production. Tlrc phosphate had shorvn an enltancing effect rvhere as citrate inhibit antibiotic production and lowercd the grolvth of the organism on cultivation media.

Antibiotics are compounds that inhibit the growth of other microorganisms by some specific interference in their normal biochemistry. The specificity of action of antibiotics for particular targets, and hence for particular groups of organisms, is the reason why many of them are so valuable in medical, veterinary, and agricultural practice, and thcrcfore, as industrial products (ll).
Biochemical analysis of the end product ' had revealed that many streptomycetes might produce more than one type of a-ntibiotics during their grorvth and development (16).
Other studies founcl that other nrolecules may have an adverse effect in antibiotic production. The Afactor (2 -sisocapryloyl -3shydroxyrnethylybutyrolacton) is a potent autoregulatory factor essential for antibiotic production and spore formation in Streptony'ces (e).
In Streptomyces, antibiotic production nearly ahvays takes place only after rapid grorvth has ceased. When nutrients are abundant and readily available, microorganisms grow fast. In mixed communities, rapid conversion of nutrients to biomass is the overriding theme of the metabolism and its efficiencv is maximized by the wellknown regulatory system that governs such assimilation. Considering this fact, Streptomyces grown in a liquid media generally produce antibiotics during stationary phase or at low growth rate. This may reflect production by cell inside mycelial pellets that may be nutritionally limited and that have, therefore. entered stationary phase ('o).Gen.i specifically involved in the production of particular antibiotic are invariably found clustered together, and only one set for methylenomycin production is known to be plasmidlocated rather than chromosomal, while most of other antibiotics were found to be chromosomally determined (5).
The biosynthetic clusters usually also contain one or more genes that confer immunity to the antibiotic which vary considerably in their mode of action. Many genes have been identified that pleiotropically affecting antibiotic production in Strcptorttyccs, and several of these arc likely to play a global role in regulation of antibiotic production. Mutants in about half of thcsc pleiotropic genes also shorved deficiencies in nrorphological di ffercntiation (8 Results and Discussion:-Antibiotic production is a common feature in Streptotnyces. It is so rare to find a bacterium of tlrese genera deficient in production of such secondary metabolite in nature, only but those deficient in aerial mycelium production as a result of mutation. This proposed a complex network connecting antibiotic production with differentiation.This proposal lcd to the discovery of plieotropic gcnes that affect differentiation as lvcll as antibiotic production (').tn normal isolates ol strcptonlycetcs, production of antibiotic nray dcpcnd mostly on physiological and nutritional conditions. l'lrc organism rvas first grorvn orr rncdia mentioncd previously to dctcct the bcst grorvth nrediunr. Results shorved R2 Mcdium, antibiotic production medium, and cornpletc ntccliunr wcrc more stritable for the grorvth of the organism, since they allolved fast grorvth and diffbrcntiation that rvas complete in 7 days, rvhcre as other media allorved gror.vth and spore forrnation in l4 days. The reason may be attributed to the presence of nitrogen and carbon sources that are easily to be consumed by the organism and enhance differentiation in shorter time. These media rvere used for further research.
The isolate sholved an antibacterial activity against grampositive, and gramnegative bacteria that may indicate the presence of an antibacterial agent produced (table l).   Growth temperature was tested as a factor affecting antibiotic production from the bacterium. Results showed that 370C represenr the best growth temperature and aniibiotic production, since no biological activity was observed when the local isolate was grown at 270C, ancl it fail to grow at qSdC.--.- The efFect of ions was also investigated as a factor controlling antibiotic production. Two types of ions referred to by Hopwood and Chater (1994) were tested phosphate and citrate.
Whcn those ions rvere added to the medium thcy sholved different effects. The citrate ion shorved an inhibition effect while the phosphate shorvcd an enhancing eftbct on antibiotic production.
This may be attributed to the intcrfcrence of tlrcsc ions rvith the primary metabolic pathrvay producing the prccursors ncedcd for tht antibacterial agent pr.oduction (a).

Conclusions:-
This study had focusecl on identification of Neornycin antibiotic produced by local StreptotrU,sgs isolate and studying factors affecting this antibiotic production thal included grow'th condition, physical, and chemical factors. Among these factors, pH shorvecl the most drastic effect on antibiotic production not only as an eflect on cell rvall permeability but it may interfere rvith other biological activities of the bacterium that need more studv.
Streptomyces strain Inhibition zone in mm against test organisms Pseudomonas