Abstract: Antibiotic 10381a.sub.1, wherein R is hydrogen, is a cytosine-containing antibiotic producible by culturing the novel microorganism Streptomyces arginensis in an aqueous medium and isolation thereof. Derivatives wherein R is a C.sub.1 to C.sub.3 alkyl ester of antibiotic 10381a.sub.1, are also disclosed along with the pharmaceutically acceptable salts of both the native and esterified forms. Antibiotic 10381a.sub.1 inhibits the growth of selected species of yeast, fungi and bacteria. This invention also relates to a novel process for the preparation of the antibiotics 10381b and to a method of using antibiotics 10381b to promote growth in meat-producing animals. These antibiotics are also obtained by the fermentation of a nutrient medium with the novel microorganism Streptomyces arginensis and are active against selected species of bacteria.

Abstract: Antibiotic 10381a.sub.1, wherein R is hydrogen, is a cytosine-containing antibiotic producible by culturing the novel microorganism Streptomyces arginensis in an aqueous medium and isolation thereof. Derivatives wherein R is a C.sub.1 to C.sub.3 alkyl ester of antibiotic 10381a.sub.1, are also disclosed along with the pharmaceutically acceptable salts of both the native and esterified forms. Antibiotic 10381a.sub.1 inhibits the growth of selected species of yeast, fungi and bacteria. This invention also relates to a novel process for the preparation of the antibiotics 10381b and to a method of using antibiotics 10381b to promote growth in meat-producing animals. These antibiotics are also obtained by the fermentation of a nutrient medium with the novel microorganism Streptomyces arginensis and are active against selected species of bacteria.

Abstract: Antibiotic 10381a.sub.1, wherein R is hydrogen, is a cytosine-containing antibiotic producible by culturing the novel microorganism Streptomyces arginensis in an aqueous medium and isolation thereof. Derivatives wherein R is a C.sub.1 to C.sub.3 alkyl ester of antibiotic 10381a.sub.1, are also disclosed along with the pharmaceutically acceptable salts of both the native and esterified forms. Antibiotic 10381a.sub.1 inhibits the growth of selected species of yeast, fungi and bacteria. This invention also relates to a novel process for the preparation of the antibiotics 10381b and to a method of using antibiotics 10381b to promote growth in meat-producing animals. These antibiotics are also obtained by the fermentation of a nutrient medium with the novel microorganism Streptomyces arginensis and are active against selected species of bacteria.

Abstract: Antibiotic 10381a.sub.1, wherein R is hydrogen, is a cytosine-containing antibiotic producible by culturing the novel microorganism Streptomyces arginensis in an aqueous medium and isolation thereof. Derivatives wherein R is a C.sub.1 to C.sub.3 alkyl ester of antibiotic 10381a.sub.1, are also disclosed along with the pharmaceutically acceptable salts of both the native and esterified forms. Antibiotic 10381a.sub.1 inhibits the growth of selected species of yeast, fungi and bacteria. This invention also relates to a novel process for the preparation of the antibiotics 10381b and to a method of using antibiotics 10381b to promote growth in meat-producing animals. These antibiotics are also obtained by the fermentation of a nutrient medium with the novel microorganism Streptomyces arginensis and are active against selected species of bacteria.