Antibacterial activity of cyclo(L-Pro-L-Tyr) and cyclo(D-Pro-L-Tyr) from <i>Streptomyces</i> sp<i>.</i> strain 22-4 against phytopathogenic bacteria

<p>Two bioactive cyclic dipeptides, cyclo(L-Pro-L-Tyr) and cyclo(D-Pro-L-Tyr), were isolated from the culture broth of <i>Streptomyces</i> sp. strain 22-4 and tested against three economically important plant pathogens, <i>Xanthomonas axonopodis</i> pv. citri, <i>Ralstonia solanacearum</i> and <i>Clavibacter michiganensis</i>. Both cyclic dipeptides were active against <i>X. axonopodis</i> pv. citri and <i>R. Solanacearum</i> with MIC of 31.25 <i>μ</i>g/mL<i>.</i> No activity could be observed against <i>C. michiganensis</i>.