High growth rate and substrate exhaustion results in rapid cell death and lysis in the thermophilic bacterium Geobacillus thermoleovorans

Spyros G. Pavlostathis, Roger Marchant*, Ibrahim M. Banat, Nigel G. Ternan, Geoffrey McMullan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Batch cultures of the thermophilic bacterium Geobacillus thermoleovorans T80 attained extremely high-specific glucose utilization rates leading to high specific growth rates, followed by extensive cell death and lysis with the onset of substrate exhaustion. The dramatic decrease in live cell numbers, as determined by flow cytometry, was accompanied by the release of soluble protein. Once the growth phase reached the point of commitment to lysis created by the impending exhaustion of substrate, the addition of extra carbon substrate did not halt the rapid death rate and lysis, although, towards the end of the exponential growth phase, the substrate was utilized producing only a small additional biomass concentration as a result of the net effect of cell growth and death. This lytic phenomenon was observed when a range of different carbon substrates (glucose, pyruvate, acetate, n-hexadecane, nutrient broth), as well as ammonium (the nitrogen source) in the presence of excess carbon source, reached near exhaustion. The rate and extent of cell death and the ensuing lysis depend on the culture growth rate. Cultures batch grown with a lower initial substrate concentration, or at a lower temperature, or at lower dilution rates for continuous-flow cultures, exhibited a lower rate and extent of cell death and lysis. Batch re-culture of the persister cells resulted in a behavior identical to that of the original culture indicating that these cells were not genetically modified. The glucose utilization, cell growth and death rates were mathematically described based on Monod kinetics and estimated values of pertinent biokinetic constants are reported.

Original languageEnglish
Pages (from-to)84-95
Number of pages12
JournalBiotechnology and Bioengineering
Issue number1
Publication statusPublished - 05 Sep 2006
Externally publishedYes


  • Cell death and lysis
  • Geobacilli
  • Kinetics
  • Soil thermophile

ASJC Scopus subject areas

  • Biotechnology
  • Microbiology


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