SummaryBacteria typically undergo intermittent periods of starvation and adaptation, emulated as diauxic growth in the laboratory. In association with growth arrest elicited by metabolic stress, the differentiating eubacterium Streptomyces coelicolor not only adapts its primary metabolism, but can also activate developmental programmes leading to morphogenesis and antibiotic biosynthesis. Here, we report combined proteomic and metabolomic data of S. coelicolor used to analyse global changes in gene expression during diauxic growth in a defined liquid medium. Cultures initially grew on glutamate, providing the nitrogen source and feeding carbon (as 2-oxoglutarate) into the TCA cycle, followed by a diauxic delay allowing reorientation of metabolism and a second round of growth supported by NH 4 + + + + , formed during prediauxic phase, and maltose, a glycolytic substrate. Cultures finally entered stationary phase as a result of nitrogen starvation. These four physiological states had previously been defined statistically by their distinct patterns of protein synthesis and heat shock responses. Together, these data demonstrated that the rates of synthesis of heat shock proteins are determined not only by temperature increase but also by the patterns and rates of metabolic flux in certain pathways. Synthesis profiles for metabolic-and stress-induced proteins can now be interpreted by the identification of 204 spots (SWICZ database presented at http:// proteom.biomed.cas.cz). Cluster analysis showed that the activity of central metabolic enzymes involved in glycolysis, the TCA cycle, starvation or proteolysis each displayed identifiable patterns of synthesis that logically underlie the metabolic state of the culture. Diauxic lag was accompanied by a structured regulatory programme involving the sequential activation of heat-, salt-, cold-and bacteriostatic antibiotic (pristinamycin I, PI)-induced stimulons. Although stress stimulons presumably provide protection during environmental-or starvationinduced stress, their identities did not reveal any coherent adaptive or developmental functions. These studies revealed interactive regulation of metabolic and stress response systems including some proteins known to support developmental programmes in S. coelicolor .
SummaryCompartmentalized gene expression during sporulation is initiated after asymmetric division by cell-specific activation of the transcription factors s s s s F and s s s s E . Synthesis of these s s s s factors, and their regulatory proteins, requires the activation (phosphorylation) of Spo0A by the phosphorelay signalling system. We report here a novel regulatory function of the antianti-s s s s F SpoIIAA as inhibitor of Spo0A activation. This effect did not require s s s s F activity, and it was abolished by expression of the phosphorelay-independent form Spo0A-Sad67 indicating that SpoIIAA directly interfered with Spo0A ~ P generation. IPTG-directed synthesis of the SpoIIE phosphatase in a strain carrying a multicopy plasmid coding for SpoIIAA and its specific inhibitory kinase SpoIIAB blocked Spo0A activation suggesting that the active form of the inhibitor was SpoIIAA and not SpoIIAA-P. Furthermore, expression of the non-phosphorylatable mutant SpoIIAAS58A (SpoIIAA-like), but not SpoIIAAS58D (SpoIIAA-P-like), completely blocked Spo0A-dependent gene expression. Importantly, SpoIIAA expressed from the chromosome under the control of its normal spoIIA promoter showed the same negative effect regulated not only by SpoIIAB and SpoIIE but also by septum morphogenesis. These findings are discussed in relation to the potential contribution of this novel inhibitory feedback with the proper activation of s s s s F and s s s s E during development.
Spore development and stress resistance in Bacillus subtilis are governed by the master transcription factors Spo0A and B , respectively. Here we show that the coding genes for both regulatory proteins are dramatically induced, during logarithmic growth, after a temperature downshift from 37 to 20°C. The loss of B reduces the stationary-phase viability of cold-adapted cells 10-to 50-fold. Furthermore, we show that B activity is required at a late stage of development for efficient sporulation at a low temperature. On the other hand, Spo0A loss dramatically reduces the stationary-phase viability of cold-adapted cells 10,000-fold. We show that the requirement of Spo0A for cellular survival during the cold is independent of the activity of the key transition state regulator AbrB and of the simple loss of sporulation ability. Furthermore, Spo0A, and not proficiency in sporulation, is required for the development of complete stress resistance of cold-adapted cells to heat shock (54°C, 1 h), since a loss of Spo0A, but not a loss of the essential sporulation transcription factor F , reduced the cellular survival in response to heat by more than 1,000-fold. The overall results argue for new and important roles for Spo0A in the development of full stress resistance by nonsporulating cells and for B in sporulation proficiency at a low temperature.The exposure of bacteria to diverse growth-limiting conditions induces the synthesis of a large set of proteins (called general stress proteins) that protect the cell against internal (metabolic) or external (environmental) stresses (22,23,29,32,33). In the gram-positive, endospore-forming bacterium Bacillus subtilis, the general stress response is controlled mainly by B , the alternative transcription factor of the RNA polymerase that brings about a special physiological state which significantly enhances bacterial survival (11,20,22,23,29,32,33,37). It is estimated that over 200 genes (5% of the coding capacity of the genome) are directly or indirectly under B control, and the loss of B function leads to multiple-stress sensitivity, compromising the survival of the B null mutant strain (23,29,32). Besides having this very important, rapid, reversible, and plastic adaptive response (22,29), B. subtilis is also able to differentiate into dormant spores when nutritional conditions become so extreme that the B -dependent response would not be adequate to guarantee the survival of the cell (19,21,24,30,31). While B is the key regulatory protein involved in the reversible adaptive stress response of vegetative cells, the master transcription factor Spo0A is the key regulator responsible for the decision of a vegetative cell to differentiate into a dormant and highly resistant new cell, i.e., the spore (31). It is accepted that these responses, general stress adaptation and sporulation, are important for the survival of B. subtilis in its natural environment, i.e., soil (29-33). Furthermore, high levels of expression of general stress proteins provide stressed or starved cells with mu...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.