Spatio-temporal expression of the pathway-specific regulatory gene redD in S. coelicolor

Abstract

Confocal laser scanning microscopy was used to observe the spatio-temporal expression of the pathway-specific gene redD during S. coelicolor cell cultivation. The corresponding mutant S. coelicolor lyqRY1522 carrying redD::eyfp in the chromosome was constructed. The temporal expression results of the fusion protein during submerged cultivation demonstrated that expression of redD began in the transition phase, continuing through the exponential growth phase to the stationary phase, and reached maximum in the stationary phase. On the other hand, redD was expressed only in substrate mycelia during solid-state culture, while aerial mycelia remained essentially non-fluorescent throughout culture. Results demonstrated that the expression pattern of redD coincides with that of the biosynthesis of the antibiotics during culture, revealing a direct correlation between the spatio-temporal distribution of regulatory gene expression and second metabolism.

Mycelium Differentiation and Antibiotic Production in Submerged Cultures ofStreptomyces coelicolor

“…This mycelium, as previously seen in the presporulating aerial mycelium in solid cultures, emerges after a death process which affects a compartmentalized mycelium (41). These results clarify data from other authors who have claimed that redD expression is correlated with secondary metabolism, but they were unable to associate it with any specific mycelial structure (67). Consequently, from a phenotypic point of view, S. coelicolor hyphae can be considered to experience a differentiation process under submerged conditions until the presporulation phase; this corresponds to the antibiotic-producing second, multinucleated, mycelium.…”

“…Most authors assume that no differentiation processes occur in submerged cultures and that antibiotics are produced by the substrate mycelium when it reaches the stationary phase (13,25,43,46,61,67). On the other hand, it is known that mycelial morphology correlates with the production of secondary metabolites, and most authors state that cellular aggregation, and therefore pellet and clump formation, is fundamental to obtaining good production.…”

“…There is a general consensus that a transient arrest of growth characterizes Streptomyces grown in submerged cultures (13,25,43,46,52,67). This growth arrest precedes antibiotic production (28) and can activate antibiotic biosynthetic genes (31,43), antibiotic resistance genes (50), and stress response stimulons (48), as well as arrest of ribosomal protein synthesis (3).…”

Pre-sporulation stages ofStreptomycesdifferentiation: state-of-the-art and future perspectives

“…Most Streptomyces species do not sporulate in liquid cultures and it was widely accepted that no morphological differentiation took place in these conditions. Secondary metabolites would be produced by the substrate mycelium at the stationary phase after a transient growth arrest (Granozzi et al, 1990;Neumann et al, 1996;Novotna et al, 2003;Zhou et al, 2005;Chouayekh et al, 2007). Despite that, sporulation was reported in liquid cultures for several streptomycetes, such as Streptomyces venezuelae (Glazebrook et al, 1990), S. griseus (Kendrick & Ensign, 1983), Streptomyces chrysomallus (Kuimova & Soina, 1981), S. antibioticus ETHZ7451 (Novella et al, 1992), Streptomyces albidoflavus SMF301 (Rho & Lee, 1994), or Streptomyces brasiliensis (Rueda et al, 2001).…”

Prodiginine Production inStreptomyces coelicolorCorrelates Temporally and Spatially to Programmed Cell Death

“…Such a broad spectrum of activity suggests that the PdGproducing species should be sensitive to their own molecules. Indeed, in Streptomyces coelicolor the onset of expression of the red cluster (encoding the PdG biosynthetic pathway) coincides with the entrance of this species into a period of growth cessationthe so-called transition phase (44)(45)(46)(47)(48)(49)(50). In addition, prodiginine production coincides with a round of massive cell death in the course of which the Streptomyces multicellular filamentous network undergoes drastic morphological changes associated with the sporulation process.…”