In Bacillus megaterium, a temperature that suppresses sporulation (43 degrees C) only slightly exceeds both the optimum growth temperature and the temperature still permitting sporulation (40-41 degrees C). Here we show that, when cells grown at 35 degrees C and transferred to a sporulation medium, were subjected to shifts between 35 degrees C and the sporulation suppressing temperature (SST, 43 degrees C), their development and proteolytic activities were deeply affected. During the reversible sporulation phase that took place at 35 degrees C for 2-3 h (T2-T3), the cells developed forespores and their protein turnover was characterized by degradation of short-lived proteins and proteins made accessible to the proteolytic attack because of starvation. During the following irreversible sporulation phase refractile heat-resistant spores appeared at T4-T5. Protein turnover rate increased again after T2 and up to T8 60-70% prelabelled proteins were degraded. The SST suppressed sporulation at its beginning; at T3 no asymmetric septa were observed and the amount of heat-resistant spores at T8 was by 4-5 orders lower than at 35 degrees C. However, the cells remained viable and were able to sporulate when transferred to a lower temperature. Protein degradation was increased up to T3 but then its velocity sharply dropped and the amount of degraded protein at T8 corresponded to slightly more than one-half of that found at 35 degrees C. The cytoplasmic proteolytic activity was enhanced but the activity in the membrane fraction was decreased. When a temperature shift to SST was applied at the beginning of the irreversible sporulation phase (T2.5), the sporulation process was impaired. A portion of forespores lyzed, the others were able to complete their development but most spores were not heat-resistant and their coats showed defects. Protein degradation increased again because an effective proteolytic system was developed during the reversible sporulation phase but the amount of degraded protein was slightly lower than at 35 degrees C. A later (T4) shift to SST had no effect on the sporulation process.

• MeSH
• Bacillus megaterium metabolismus   ultrastruktura   MeSH
• bakteriální proteiny metabolismus   MeSH
• endopeptidasy metabolismus   MeSH
• kinetika MeSH
• spory bakteriální metabolismus   ultrastruktura   MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• endopeptidasy MeSH

Bacillus subtilis 115 grew in a medium with amino acids and glucose with the maximum specific growth rates mu of 1.20-1.10/h in the temperature range of 45-48 degrees C. Activity of the extracellular neutral proteinase excreted by 1.3 mg/mL dry mass during 8 h of the postexponential and stationary growth phases decreased from its maximum value of 0.23 TU/mL at 40 degrees C to 0.13 and 0.06 TU/mL at 45 and 48 degrees C, respectively. Formation of the extracellular serine proteinase decreased even more - from 0.18 TU/mL at 40 degrees C to 0.06 and 0.03 TU/mL at 45 and 48 degrees C, respectively. Sporulation, expressed as the portion of sporangia with refractile spores at the 6th h of the stationary phase decreased from 46% at 40 degrees C to 17 and 3% at 45 and 48 degrees C, respectively.

• MeSH
• Bacillus subtilis fyziologie   MeSH
• buněčné dělení MeSH
• endopeptidasy biosyntéza   MeSH
• metaloendopeptidasy biosyntéza   MeSH
• spory bakteriální fyziologie   MeSH
• subtilisiny biosyntéza   MeSH
• vysoká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• endopeptidasy MeSH
• metaloendopeptidasy MeSH
• subtilisiny MeSH

We studied the effect of temperature on the production of an extracellular neutral metalloproteinase of Bacillus megaterium in a laboratory fermentor under constant aeration and pH. The optimal temperature for growth (35-38° C) was higher than that for the synthesis of proteinase during exponential growth (below 31° C). The critical biomass concentration at which the exponential growth terminated decreased with increase in cultivation temperature. The specific rate of proteinase synthesis decreased when the critical biomass concentration was achieved. The observed decrease in proteinase synthesis was related to the cultivation temperature. The temperature also influenced the level of mRNA coding for proteinase. We formulated a mathematical model of cultivation describing the dependence of growth and proteinase synthesis on dissolved oxygen and temperature. The parameters of the model were identified for temperature intervals from 21 to 41° C using a computer. The optimum temperature for the enzyme production was 21° C. The productivity (enzyme activity/time) was maximal at 24-28° C. When optimizing the temperature profile of cultivation, we designed a suboptimal solution represented by a linear temperature profile. We have found that under conditions of continuous decrease in temperature, the maximal production of the proteinase was achieved at a broad range of temperature (26-34° C) when the rate of temperature decrease was 0.2-0.8° C/h. The initial optimal temperature for the enzyme productivity was in the range of 32-34° C. The optimum temperature decrease was 0.8° C/h.

• Publikační typ
• časopisecké články MeSH