tmRNA of Streptomyces collinus and Streptomyces griseus during the growth and in the presence of antibiotics.
Bottom Line: These findings suggest that produced antibiotics induce tmRNA that facilitate reactivation of stalled complex of ribosomes and maintain viability.The effect of antibiotics that inhibit the cell-wall turnover, DNA, RNA or protein synthesis on the level of tmRNA was examined.Antibiotics interfering with ribosomal target sites are more effective at stimulation of the tmRNA level in streptomycetes examined than those affecting the synthesis of DNA, RNA or the cell wall.
Affiliation: Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.Show MeSH
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Mentions: Total RNA was isolated from submerse cultures and aliquots (50‚ÄÉ¬Ķg) were analysed in polyacrylamide‚Äźurea gels. Northern blots were probed with labelled ssrAs and quantified. Growth of S. griseus in medium GYM reaches its maximum between 36 and 38‚ÄÉh of cultivation and production of streptomycin started between 20 and 24‚ÄÉh (Fig.‚ÄÉ1A). During the exponential phase of growth (14‚ÄÉh), the highest level of tmRNA was detected and further development was accompanied with decline in the tmRNA level. Growth of S. collinus producing kirromycin reaches its maximum at 36‚ÄÉh cultivation and tmRNA level increases gradually up to 48‚ÄÉh and then decreases near the initial value found in the 14‚ÄÉh cultivation (Fig.‚ÄÉ1B). The amount of tmRNA during exponential phase of growth was about four times higher than that found in S. griseus. In parallel experiments that were performed with the same cultures, we followed the amount of 5S RNA to ascertain whether the decrease in the tmRNA is not due to general loss of RNA. No significant changes in the 5S RNA levels were observed during the development of cultures. The decrease in tmRNA during the late exponential phase of growth suggests that the tmRNA was degraded. To test this possibility the half‚Äźlife of tmRNA from the exponentially growing cells (14‚ÄÉh cultures) and the cells from stationary phase of growth (40‚ÄÉh and 68‚ÄÉh cultures) were determined by inhibition of transcription with rifampicin and the decay of tmRNA was measured. In cells of S. griseus (Fig.‚ÄÉ2A) from exponential phase of growth, the presence of rifampicin (300‚ÄÉ¬Ķg‚ÄÉml‚ąí1) caused complete inhibition of RNA synthesis and about 10% tmRNA was degraded after 60‚ÄÉmin cultivation. Significantly lower stability of the tmRNA was found in cultures from stationary phase of growth. In contrast, the level of tmRNA of S. collinus (Fig.‚ÄÉ2B) was stable from 14 to 68‚ÄÉh cultivation and the half‚Äźlife of the tmRNA in the presence of rifampicin was longer than 50‚ÄÉmin. These data show differences in abundance and stability of tmRNA during development of the two streptomycetes strains examined.
Affiliation: Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.