Strains 4F and 2C grew on MS medium at 37°C and 45°C faster than the mesophilic Streptomyces strains at 30°C and 37°C (Figure 2). To measure the growth rates of 4F and M145, equal numbers of spores were inoculated into TSB liquid medium, and three mycelial samples were harvested at various points during the time course. Each sample was weighed, and the three values were averaged for a particular time point. As shown in Figure 3, 4F rapidly accumulated biomass to a maximum at 45°C or 37°C within 16 h, then the growth curve fluctuated, and the final biomass

of strain 4F is higher for M145 (especially at 45°C). The oscillations shown at 37 and 45°C resembling EX 527 molecular weight the “”death/growth process”" of S. coelicolor A3(2) in liquid medium with a diluted inoculum [26]. The doubling times of growth for 4F at 30,

37, 45 and 50°C and M145 at 30°C and 37°C in each logarithmic phase (14-20, 6-12, 8-14 and 12-18 h for 4F at 30, 37, 45 and 50°C, and 16-22 for M145 at 30 and 37°C) were 2.3, 1.4, 1.1 2.3, 2.2 and 2.4 h, respectively. Thus strain 4F grew at 45°C twice and at 37°C 1.6 times as fast as M145 at 30°C in TSB medium. Figure 3 Growth curves of 4F and M145 in liquid culture at four temperatures. The curves are based on the average of three weighings at each time point, and standard deviations are indicated. Figure 4 Quantitation of JNK-IN-8 actinorhodin production by M145 and by 4F containing the cloned actinorhodin gene cluster in liquid AC220 medium. About 1 × 106 spores of M145 and of 4F containing pCWH74 were inoculated into 50 ml R2YE liquid medium (lacking KH2PO4 and CaCl2) at 30 and 37°C. Samples of 1 ml culture were harvested in a time-course and treated with KOH; absorption at OD640 indicated actinorhodin production. Identification of one linear and three circular plasmids among 41 strains, and sequencing of pTSC1 We detected three circular plasmids, 7-kb pTSC1, from X4-3, 7.5-kb pTSC2

from X3-3, and 40-kb pTSC3 as well as 16-kb linear pTSL1 from T6-1-4. The complete nucleotide sequence of the circular pTSC1 consisted filipin of 6996 bp (GenBank accession number GU271942), with 72% G+C, resembling that of a typical Streptomyces genome (e.g., 72.1% for S. coelicolor A3(2): [27]). Eight ORFs (open reading frame) were predicted by “”FramePlot 3.0 beta”" [28]; seven of them resembled Streptomyces or Mycobacterium genes (Additional file 1, Table S1). Notably, three genes resembled the transfer and spread genes (tra and spd) of Streptomyces plasmids pIJ101 [29] and pSNA1 [30]. Development of a gene cloning system in strains 2C and 4F Followed the standard protocols of preparation and transformation of Streptomyces protoplasts with slight modifications (see Methods), pTSC1-derived pCWH1 (see Methods and Table 2) was introduced by transformation into ten well-sporulating thermophilic Streptomyces strains. Thiostrepton-resistant colonies were obtained for strains 2C and 4F at frequencies of 1.