Life‐cycle kinetic model for endospore‐forming bacteria, including germination and sporulation

Abstract

We develop a mechanistic life-cycle model for endospore-forming bacteria (EFB) and test the model with experiments with a Bacillus mixed culture. The model integrates and quantifies how sporulation and germination are triggered by depletion or presence of a limiting substrate, while both substrates affect the rate of vegetative growth by a multiplicative model. Kinetic experiments show the accumulation of small spherical spores after the triggering substrate is depleted, substantially more rapid decay during sporulation than for normal decay of vegetative cells, and a higher specific substrate utilization rate for the germinating cells than that for growth of vegetative cells. Model simulations capture all of these experimental trends. According to model predictions, when a batch reactor is started, seeding with EFB spores instead of active EFB delays the onset of rapid chemical oxygen demand (COD) utilization and biomass growth, but the end points are the same. Simulated results with low aeration intensity show that germination can consume some substrate without dissolved oxygen (DO) depletion.

Microbial enhanced oil recovery—a modeling study of the potential of spore-forming bacteria

“…Different approaches to the sporulation process have been presented, but they mainly resulted in the sigmoidal curves to describe the triggering [53,54]. Reactivation has been modeled in a manner similar to sporulation, where the triggering of reactivation also depends on the substrate concentration [53].…”

“…The triggering function, or rate function, is a sigmoidal curve [53] (also called the logistic function). The sigmoidal nature of the response comes from the allosteric behavior of enzymes and transcription factors involved in the phosphoelay [19,29].…”

“…Reactivation has been modeled in a manner similar to sporulation, where the triggering of reactivation also depends on the substrate concentration [53].…”

“…They can rather be found in the water phase where they are transported to better conditions for survival [16,22]. The spores can stay as such for a long time and become reactivated only when the conditions are favorable [16,44,53].…”

“…Bacteria cope with the stress to ensure a better chance of survival. For sporeforming bacteria, the last option for survival is sporulation [5,16,44,53]. Spores are smaller, dormant (non-growing) versions of vegetative bacteria, which can survive in very harsh environments [41].…”