[The sensitivity to landomycins A and E of streptomycetes, producers of polyketide antibiotics].

Streptomycetes, which are the producers of different polyketide antibiotics, can be divided into 4 groups as to their sensitivity to landomycins A and E: 1) S. glaucescens Tü49, producer of tetracenomycin and S. aureofaciens 019, producer of chlortetracycline belong to the most landomycin-sensitive strains. 2) S. cyanogenus S136, producer of landomycin A, and S. lividans TK24, producer of actinorhodin, were sensitive to mean and high doses of landomycin E (more than 60-80 ug/ml). 3) S. globisporus 1912 (producer of landomycin E), S. cyanogenus S136, S. fradiae Tü2717, producer of urdamycins and S. coelicolor A3(2), producer of actinorhodin have moderate sensitivity to all doses of the both antibiotics but strain S136 only to low doses. 4) Resistance to landomycins A and E was observed in strain S. olivaceus Tü2353, producer of elloramycin. In all the experiments landomycin E showed the 1-2 orders higher lethal activity in comparison with landomycin A which molecule is composed of the same aglycon landomycenone A but a longer polysaccharide chain which probably hampers the penetration of antibiotic through the cell membrane.