Occurrence of the Stringent Response in Streptomyces sp. and its Significance for the Initiation of Morphological and Physiological Differentiation

Abstract

Streptomyces sp. MA406-A-1 produced formycin (a nucleoside antibiotic) in parallel with cell growth in a synthetic medium. When the synthetic medium was supplemented with 1 % (w/v) Casamino acids, however, formycin was produced only after the end of exponential growth. The intracellular ppGpp pool increased gradually towards the end of exponential growth and was maximal at the beginning of formycin production. After shift down from Casamino acids medium to synthetic medium, the ppGpp pool increased immediately, while the GTP pool decreased ; under such conditions, the ability to produce formycin increased eightfold. Relaxed (re0 mutants, the first isolated for a Streptomyces species, were found at high incidence (10%) among spontaneous thiopeptin-resistant isolates and had severely reduced abilities to accumulate ppGpp. These re1 mutants also failed to produce formycin under the usual culture conditions and exhibited numerous pleiotropic effects such as an inability to produce melanin and an extended delay of aerial mycelium formation. Thus Streptomyces sp. exhibited a typical stringent response, and the response initiated (or was needed for) the induction of secondary metabolism. The response may have also participated in the initiation of aerial mycelium formation by decreasing the intracellular GTP pool.

Guanine Nucleotides Guanosine 5′-Diphosphate 3′-Diphosphate and GTP Co-operatively Regulate the Production of an Antibiotic Bacilysin in Bacillus subtilis

“…The stringent response, a general and ubiquitous response to nutritional environmental stress in prokaryotic microorganisms, is mediated by the unique nucleotide ppGpp (1). By analyzing mutants with an impaired ability to elicit the stringent response, Ochi proposed that ppGpp plays a role in triggering the onset of antibiotic production in Streptomyces spp., whereas morphological differentiation is triggered by detecting a reduced amount of GTP (5,16,41,42). The most interesting observation in the present study is that GTP, in addition to ppGpp, is the key factor for initiating antibiotic production in B. subtilis as demonstrated by the addition of decoyinine and by CodY disruption experiments (Figs.…”

Streptomyces clavuligerus relA-null mutants overproduce clavulanic acid and cephamycin C: negative regulation of secondary metabolism by (p)ppGpp

“…Nucleotides were extracted as described by Ochi (1986). Samples of the cultures taken from 0 to 60 min after shift-down were quickly filtered as above and the filters submerged upside-down in ice-cooled 1 M formic acid in a Petri dish.…”

“…Nucleotide levels in S. clavuligerus ATCC 27064 and in the DrelA : : neo mutant S. clavuligerus wild-type and DrelA : : neo were grown in SA medium and their ATP, GTP and polyphosphorylated nucleotide levels determined (Ochi, 1986). Samples were taken from the same cultures to measure clavulanic acid and cephamycin C production, and for S1 nuclease analysis of the expression of antibiotic biosynthesis genes (see later).…”

Two relA/spoT homologous genes are involved in the morphological and physiological differentiation of Streptomyces clavuligerus

“…The filter cakes were transferred to 10 ml formic acid, incubated at 4 uC for 1 h and centrifuged for 10 min at 6000 g. The supernatants (formic acid-extractable fractions) were clarified by filtration using a 0?45 mm filter and freeze-dried. The amount of ppGpp, pppGpp and GTP was determined by HPLC using a Partisil-10 SAX (4?66250 mm) column (Whatman) as described previously (Ochi, 1986).…”

“…(Ochi, 1986(Ochi, , 1987Strauch et al, 1991;Bascaran et al, 1991;Hoyt & Jones, 1999). However, when the (p)ppGpp synthetase-encoding gene (relA) of Streptomyces coelicolor A3(2) was characterized (Chakraburtty et al, 1996), a null mutation in the relA gene failed to produce actinorhodin and undecylprodigiosin under conditions of nitrogen limitation (Chakraburtty & Bibb, 1997).…”