Antibiotics produced by microorganisms

Ouglone is the only quinone identified as an allelopathic compound from higher plants (5). It is produced by walnut trees and is a potent inhibitor. Numerous antibiotics produced by microorganisms are quinones, including the tetracycline antibiotics such as aureomycin (80). 

For control of some pest problems, materials from natural sources have proved extremely successful. In particular, many plant, human, and animal diseases are controlled by antibiotics produced by microorganisms. Insecticides from plant sources have been used effectively for many years, but the scale on which they have been used does not compare with that of the synthetic organic insecticides Introduced in the years following World War II. 

To date, several naturally occurring organoboron compounds have been identified all of these are boroesters. These compounds include antibiotics produced by microorganisms (Dunitz etal. 1971, Sato etal. 1978, Schummer etal. 1994), the plant cell wall component, rhamnogalactur-onan-II (O Neill etal. 1996, Matoh 1997), and a bacterial extracellular signaling molecule (Ghen et al. 2002). 

Antibiotic A specific type of chemical substance that is administered to fight infections usually caused by bacteria, in humans or animals. Many antibiotics are produced by microorganisms some are chemically synthesized. 

All of the transport systems examined thus far are relatively large proteins. Several small molecule toxins produced by microorganisms facilitate ion transport across membranes. Due to their relative simplicity, these molecules, the lonophore antibiotics, represent paradigms of the mobile carrier and pore or charmel models for membrane transport. Mobile carriers are molecules that form complexes with particular ions and diffuse freely across a lipid membrane (Figure 10.38). Pores or channels, on the other hand, adopt a fixed orientation in a membrane, creating a hole that permits the transmembrane movement of ions. These pores or channels may be formed from monomeric or (more often) multimeric structures in the membrane. 

Originally, the term antibiotics referred to substances produced by microorganisms that suppressed the growth of other organisms. Today, the term antibiotics often includes synthetic antimicrobial agents. 

Apropos nomenclature antibiotics are produced by microorganisms (fungi, bacteria) and are directed against life at any phylogenetic level (prokaryotes, eukaryotes). Chemotherapeutic agents originate from chemical synthesis. This distinction has been lost in current usage. 

Antibiotics are essentially natural compounds produced by microorganisms that are capable of inhibiting growth of pathogenic microbes, bacteria, and a few of the more simple microorganisms. 

Many antibiotics produced by various microorganisms are nucleosides (2). Among these are nebularine, cordycepin, and nucleocidin. The only known purines in higher plants shown to be involved In allelopathy are caffeine, theophylline, paraxanthine, and theobromine from the coffee tree... 

This was the first report of the successful screening of antibiotics for antitumor activity. Antibiotic research was thus expanded to also cover antitumor research. The term antitumor antibiotics was coined to include those compounds that are produced by microorganisms and inhibit the growth of tumor cells and tumors. Since that time, I have been continuing the study of new antitumor 2Uitlbiotics. Up to now with my collaborators I discovered eibout 65 antitumor antibiotics and elucidated structures of about 50 of them. Among them, bleomycin which we discovered in 1966 (76,79) has been used in the treatment of Hodgkin s lymphoma, tumors of the testis, and carcinomas of the skin, head, neck, and cervix. 

Penicillins, such as penicillin G and cephalosporins, such as cephalexin, as well as most other antibiotics, are produced by microorganisms that can be mass-produced in large vats. The antibiotics are then harvested and purified. 

Caffeine is one more example of compounds belonging to the purines. Evenari (21) has reported that it is one of the potent inhibitors of seed germination. Several substituted purines and nucleosides produced by microorganisms are effective antibiotics (see the Section 11). They include nebularine, cordycepin and nucleocidine which may also possess growth-inhibiting properties, as is the case with other antibiotics (Figure 10). 

Sulbactam sodium is semi-synthetic antibiotic of penicillinic group. Start material for it s synthesis is 6-aminopenicillanic acid. First 6-aminopenicillanic acid was isolated in 1957 year from benzylpenicilline as resalt of treating of it by penicillinaze. Benzylpenicilline is produced by microorganism of genus Streptomyces. 

The term antibiotic is broad and is defined as a substance produced by microorganisms that has the capacity of inhibiting the growth of and even of destroying other microorganisms by the action of very small amounts of the substance. 

Some saccharides are branched and these types are found as constituents of various natural products. For example, D-apiose occurs widely in plant polysaccharides. Antibiotics produced by the microorganism Streptomyces are another rich source of branched chain sugars. 

Following antibiotics production, microbial industrial fermentations have been used for the production of different metabolites endogenously produced by microorganisms, e.g., enzymes for different applications and large-scale production of bioethanol for fuel usage. 

In 1939, principally as an academic exercise, Florey and Chain undertook an investigation of antibiotics, i.e. substances produced by microorganisms that are antagonistic to the growth or life of other microorganisms. They prepared penicilltn and confirmed its remarkable lack of toxicity. ... 

Phenoxazinone production was as well observed in incubation media of Secale cereale, but not in such of Vida faba and Triticum aestivum [180]. The compounds can be detected is well in incubation media of several dicotyledonous species [187]. Since surface sterilization of oat caryopses with NaOCl did not prevent phenoxazinone production, it is possible that the responsible microorganism(s) are located within the caryopses. Phenoxazinone itself has an inhibitory effect on oat radicle elongation, probably caused by intercalation of the phenoxazinone ring system to DNA, as it is known from the phenoxazinone ring system of the transcription inhibitor actinomycin D, an antibiotic produced by Strepto-myces species. 

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