Differentiation of Streptomyces coelicolor A3(2) under nitrate-limited conditions

Abstract

The life cycle of Streptomyces coelicolor during development on solid medium has been studied from a physiological perspective. A biphasic growth pattern was demonstrated, evidenced by a continuous transition from an initial exponential growth period into a slower phase of biomass accretion. The switch between the two phases coincided with the exhaustion of nitrate from the medium. The depletion of nitrate from the medium coincided with the initiation of aerial mycelium formation within the cultures and the development of hydrophobic surface properties. During secondary growth, cultures remained metabolically active, continuing to accumulate DNA, despite a cessation in the levels of RNA and cell protein accretion. In addition, the accumulation of glycogen and lipid contributed to the observed accretion of biomass in this phase. The depletion of nitrate also marked an increase in the production of a-ketoglutarate by the culture and a coincident decrease in medium pH. Latter stages of the secondary growth phase saw the development of spores within the culture, this in turn was associated with a decrease in cellular glycogen. This supported previous observations that glycogen degradation and spore maturation were intimately associated.

Oxygen-Dependent Control of Respiratory Nitrate Reduction in Mycelium of Streptomyces coelicolor A3(2)

“…When growing as colonies on such minimal medium (or as cell aggregates in liquid culture), the possibility of a temporary intracellular nitrite accumulation cannot be excluded. Indeed, our studies on the differentiation of S. coelicolor A3(2) on such solid medium also demonstrated a negative influence of nitrite on sporulation, which was previously ascribed by other authors to nitrate limitation (42). The findings reported here revealed a strong developmental effect of nitrite accumulation in our rich solid medium assay and suggest that this hypothetical nitrate limitation might instead be due, at least in part, to nitrite toxicity.…”

Study of the bldG locus suggests that an anti-anti-sigma factor and an anti-sigma factor may be involved in Streptomyces coelicolor antibiotic production and sporulation The GenBank accession numbers for the sequences reported in this paper are AF134889 and AL035636

“…Of particular note is bldB, which encodes a putative DNA-binding regulatory protein and mutations in which, along with many of the other bld mutations (bldA, -B, -C, -D, -G and -H), causes a deregulation of carbon utilization (Pope et al, 1996). That these mutants activate the gal operon promoter under conditions where it is normally repressed, is consistent with the idea that a change in metabolic state is associated with the onset of aerial mycelium formation (Karandikar et al, 1997 ;Nodwell et al, 1999). This idea is further supported by the finding by Susstrunk et al (1998) that mutations in the adenylate cyclase gene, cya, which result in a classic bald phenotype, also cause a medium pH decrease, suggesting that the onset of differentiation involves a switch in metabolism to utilize organic acids released to the medium.…”

Duplicated gene clusters suggest an interplay of glycogen and trehalose metabolism during sequential stages of aerial mycelium development in Streptomyces coelicolor A3(2)

“…Glycogen accumulates biphasically over time (e.g. Karandikar et al 1997;MartõÂ n et al 1997). This is correlated with its observed accumulation in two locations in colonies: in the older parts of the substrate mycelium, from which aerial hyphae emerge (phase I accumulation); and in immature spore chains (phase II accumulation) (BranÄ a et al 1986;Bruton et al 1995;Plaskitt and Chater 1995;MartõÂ n et al 1997).…”

“…Glycogen appears to be virtually absent from the stalks of aerial hyphae and the mature spores. On the other hand, trehalose appears to be present at all growth stages, though there are disparities between available data with respect to its relative Mol Gen Genet (2000) 263: 543±553 abundance at dierent growth stages in dierent streptomycetes: in S. antibioticus, trehalose levels are relatively high in aerial hyphae and, particularly, in spores (BranÄ a et al 1986), whereas in S. coelicolor the highest levels coincide with the most rapid growth phase (Karandikar et al 1997). The periods of maximum abundance of the two carbohydrates given in published reports do not coincide.…”