~ ~~A transitory cessation of growth was recorded in Sfrepfomyces coelicolor A3(2) at the end of vegetative mycelium formation on solid medium. In the same phase a striking reduction in protein and nucleic acid synthesis was detected. Growth and macromolecular synthesis resumed, nearly reaching the original values, when morphological differentiation occurred. It is concluded that a physiological stress occurs within the bacterial population just before the onset of the morphological differentiation.
In Streptomyces coelicolor A3(2) the whiB and whiG genes are essential for sporulation, their deduced products being a possible transcriptional activator and an RNA polymerase sigma factor, respectively. In a survey of DNA from diverse actinomycetes by Southern blotting, all samples tested hybridized with whiB, but only those representing genera capable of producing sporulating aerial mycelium hybridized with whiG. It is postulated that whiB may play a more intimate role in hyphal fragmentation processes (including sporulation) than whiG. The whiB and whiG homologues (whiB-Stv and whiG-Stv) of Streptoverticillium griseocarneum were cloned and sequenced, and subjected to functional tests in S. coelicolor whiB and whiC mutants. The genes were closely similar, but not identical, to their S. coelicolor counterparts at the DNA and deduced protein levels, and both Stv. griseocarnum gene products could function well in S. coelicolor. However, studies with hybrid transcription units suggested that the promoter region of whiB-Stv is somewhat inefficient in S. coelicolor.
Teicoplanin is a glycopeptide antibiotic, produced by Actinoplanes teichomyceticus, active against Gram positive bacteria and recently introduced into clinical practice. It blocks cell wall biosynthesis by inhibiting peptidoglycan polymerization. The mechanism(s) of resistance of the producer strains of this class of antibiotics have not yet been characterized. We have constructed a genomic bank of A. teichomyceticus in Streptomyces lividans. A clone from this bank, pTR168, was able to confer resistance to teicoplanin on its sensitive host. The restriction map of plasmid pTR 168 and the hybridization pattern to A. teichomyceticus DNA were determined; we have also studied the mechanism of this resistance which seems correlated with a reduced binding of the antibiotic to the cell wall.
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