Observation of the null mutants of cmdA-F orthologues in S. lividans and SAV4098 - 4103 genes in S. avermitilis under scanning electron microscopy. (A) S. lividans ZX7 and its cmdA-F null mutant were cultured on MS at 30°C for 5 days, and then subjected to observation by scanning electron microscopy. The mutant produced less abundant aerial mycelium, most of which consisted of relatively short spore chains (white arrows). (B) Observation of S. avermitilis NRRL8165 and a null mutant of the SAV4098-4103 genes. Short aerial hyphae are indicated by white arrows.