Interferometry imaging of microbial communities

Light intensity of the measurement

2D Topography

1D Profiles

Vertical growth timelapse

Qualitative behavior and some key insights

• (A) and (B) show the representative dynamics, with two regimes separated by a characteristic length scale L
• (C) and (D) show that nutrient depletion is not the limiting factor for vertical growth.
• (E) Diffusion of a limiting nutrient recovers the two regime dynamics

Interface model, the
extra-simplified version

• Available region that can grow, due to diffusion inside the colony, is approximated as $\text{min}(h,L)$.
• No explicit nutrient dependency since it is not the limiting factor.
• Recovers the two regimes, and is simple enough that you may actually use it!

Colony height

Growth rate

Limiting length

Decay rate

Model predicts steady-state heights accurately

• Additional measurements were performed on new colonies, measured every 2 days, for a 2 week period.
• 48 hours of data may not be enough to narrow down all the parameters
• RMSE between the fits barely changes in the 48h period, hinting that while the model is correct, prediction may be
  below the real values

48h only fit

Interface model
describes growth of
varied microbes

• Gram positivity-negativity, different shapes and sizes are OK!
• EPS production does not change dynamics either
• And neither does being aerobic or anaerobic!

All the details, data, derivations, and many more figures soon with the preprint!

Pablo Bravo

pbravo7@gatech.edu