A54145is a complex of new lipopeptide antibiotics that inhibits Gram-positive bacteria and acts as a growth promotant for broiler chicks. Eight factors; A, B, C, D, E, F, At and B^have been isolated and characterized. They contain four similar peptide nuclei, each of which is acylated with either an 2-decanoyl, rc-decanoyl, or undecanoyl side chain. Taxonomicstudies ascertained that the producing microorganism was a strain of Streptomyces fradiae. Fermentation studies determined that superior antibiotic yields were obtained in stirred bioreactors in a soybean flour-molasses medium employing a continuous glucose feed. These findings, interwoven with the selection of hyper-productive mutants, increased fermentation yields from < 50 /xg/ml to more than 1 mg/ml. An analytical HPLCsystem was developed for the identification and subsequent quantitation of each factor of the A54145 complex.While screening actinomycetes for novel antimicrobial substances, a new culture was isolated from a soil sample collected in Mexico. This isolate produced a complex of lipopeptide antibiotics from which eight factors; A, B, C, D, E, F, Ax and Bx; were isolated and characterized1*.These factors contained four different cyclic peptide nuclei which varied only in valine/isoleucine and/or glutamate/3-CH3-glutamate substitutions. The TV-terminus of each nucleus was acylated with either an 2-decanoyl (z"C10), rc-decanoyl («C10), or undecanoyl (flCn) lipid side chain (Fig. I)1'2*. Major factors were A and Bl9 both of which contained the zC10 fatty acyl units. Although four additional factors could presumably be produced by this combination of nuclei and side chains, these additional factors were not isolated. A54145B,Bl9 C and E exhibited in vitro MICvalues of 0.5~2/zg/ml vs. various strains of Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus. Factors A and B were also shown to be active vs. these organisms in mice3). The factors additionally increased weight gain and feed efficiency in swine and fowl, being especially effective in chicks and turkeys (R. Wellenreiter, personal communication). A natural variant of the original isolated, NRRL18158, was characterized as a strain of Streptomycesfradiae. This paper describes taxonomy and fermentation studies on the A54145-producing cultures and the analytical HPLCsystem developed to monitor the A54145 factors.
Materials and Methods
Cell Wall AnalysesDiaminopimelic acid (DAP) isomers were determined by the method of Becker et al.4). Cell wall sugars were identified by the procedure of Lechevalier5).
Taxonomic MethodsThe methods and media recommended by the International Streptomyces Project (ISP)6) for characterization of Streptomyces species were followed. Color names were assigned to reverse pigments
