Environmental signals triggering methylenomycin production by Streptomyces coelicolor A3(2)

Abstract

Methylenomycin production by Streptomyces coelicolor A3(2) may be triggered by either of two environmental signals: alanine growth-rate-limiting conditions and/or an acidic pH shock. The production of this SCP1-encoded antibiotic was studied by using batch and chemostat cultures. Batch cultures indicated a role for both nutritional status and culture pH in its regulation. Steady-state methylenomycin production and transcription of an mmy gene under alanine but not glucose growth-rate-limiting conditions was demonstrated in chemostat culture. Transient mmy expression and methylenomycin production occurred following an acidic pH shock. This stimulation of methylenomycin production occurred independently of the nutritional status of the growth environment. Antibiotic production was partially suppressed under alanine compared with glucose growthrate-limiting conditions following the acidic pH shock. A low specific growth rate was a prerequisite for both steady-state and transient production of methylenomycin.The traditional view of antibiotic production in Streptomyces bacteria is that it is restricted to the stationary phase (idiophase) of the batch growth cycle and is triggered by environmental factors which give rise to this state (reviewed in reference 2). This view has arisen from the extensive use of batch culture in academic studies and industrial processes. To decipher the mechanisms whereby Streptomyces bacteria sense changes in their environment and transduce them into expression of specific secondary metabolic gene sets, it is essential to clearly define the environmental conditions which trigger antibiotic production. The dynamic behavior of batch cultures (23) hinders this effort.A number of authors (1,8,10,16,18,21,24,28,31,32) have studied antibiotic production by streptomycetes by using chemostat culture. From these studies, it is clear that secondary metabolism is not strictly associated with zero growth (22) and that antibiotic production is subject to a growth rate dependence. Also, in a number of cases, antibiotic production has been demonstrated to be influenced by the nutritional status of the growth environment and hence is dependent on a type of catabolite repression or metabolite interference (2). However, in many cases, researchers have reported the presence of metabolite interference based solely on studies using batch culture.The antibiotic methylenomycin is one of at least five secondary metabolites synthesized by Streptomyces coelicolor A3(2) (33). Its biosynthetic genes (mmy), together with a resistance determinant (mmr), are all carried on a large, linear plasmid, SCP1 (17). In a previous report (12), we described a set of nutritional conditions which permitted the biosynthesis of methylenomycin in batch culture. Methylenomycin was produced toward the end of the active growth phase but prior to the complete consumption of the growth stoichiometrically limiting substrate, alanine. In these experiments, the pH was not controlled and decreased during the growth phase from 7.2 to 5.5. Low...

Bioprocess Intensification for Production of Novel Marine Bacterial Antibiotics Through Bioreactor Operation and Design

“…Similarly, P. fluorescens phenazine production declined rapidly at pH 8, after an optimum at pH 7 (Slininger and Shea-Willbur, 1995). Hays et al (1997) used pH as a stressor to induce methylomycin synthesis by Streptomyces sp., a technique that merits further investigation as a bioprocess intensification tool.…”

The Application of Regulatory Cascades in Streptomyces: Yield Enhancement and Metabolite Mining

“…S. coelicolor can produce ectoine and 5hydroxyectoine under high salt conditions and temperature stress (Bursy et al, 2008). Methylenomycin production can be activated in S. coelicolor by either alanine growth-rate-limiting conditions and/or acidic pH shock (Hayes et al, 1997).…”

Deletion of the signalling molecule synthase ScbA has pleiotropic effects on secondary metabolite biosynthesis, morphological differentiation and primary metabolism in Streptomyces coelicolor A3(2)

“…Overexpression of csp1 (homologue to scoF4) of Streptomyces hygroscopicus in S. coelicolor has been reported to induce overproduction of both Red and Act (Martinez-Costa et al, 2003). Furthermore, several studies have been carried out to increase antibiotic production by shock stimuli, for example heat, cold, oxidative or osmotic stress (Hayes et al, 1997;Mikulik et al, 1999;Kim et al, 2000;Sevcikova and Kormanec, 2004), and it is widely known that stress induces antibiotic production. Also the pleiotropic regulator afsS was found upregulated in M751.…”