Oscillations in soil bacterial redox reactions

Modelling spatial oscillations in soil borehole bacteria

“…We have used simple Monod uptake terms with maximal uptake rates r i , half-saturation constants K i , yield coefficients Y i , and linear death rates with coefficients d i , for the bacteria. We have ignored an additional source term for complex carbon released upon death by organic material, involving a conversion ratio ζ, which is noted in Fowler et al (2014) can lead to chaotic oscillations if ζ a0.…”

“…The latter would provide a source term in the equation, and following Fowler et al (2014), we take this source S to be constant.…”

“…We non-dimensionalise the equations in the same way as Fowler et al (2014), additionally choosing an appropriate length scale:…”

“…Parameter values are listed in Table 1; these are as given by Fowler et al (2014), with the additional choice of a diffusion coefficient D of $ 10 À 9 m 2 s À 1 . Most of the parameter values are taken from Langergraber et al (2009).…”

“…In recent work, Fowler et al (2014) suggested that one mechanism whereby such oscillatory profiles could occur was through a competitive interaction between respiring heterotrophic and fermentative bacteria. In conditions of limited nutrient supply, self-sustained oscillations in both microbe species and nutrient carbon source can occur in a Continuous Stirred Tank Reactor (CSTR) model, suggest that when this model is studied in a spatially inhomogeneous medium, the effects of diffusion may cause oscillatory waves to occur, corresponding to the spatial oscillations which are actually seen.…”