I am currently studying strict aerobic bacteria and encountering challenges with the growth rate in broth cultures. Despite using an inoculum size of 4-5 colonies, a low broth volume (4-5 ml), and maintaining a 24-hour incubation period, the observed growth appears to be disproportionately light. The incubator at my disposal is a gravity convection incubator without shaking capabilities. The tubes utilized have screw caps, but these caps are intentionally kept loosened.
Gravity convection incubators are suitable for many general-purpose incubation needs, including the cultivation of aerobic bacteria, there could be variations in oxygen and temperature distribution that may affect growth. strict aerobic bacteria may prefer using a mechanical convection incubator with a more uniform temperature and oxygen distribution to ensure optimal conditions for growth.
When you recover the growth, are the cells settled to the bottom of the tube as a pellet? Or are there any planktonic cells floating near the surface or attached to the tube wall at the meniscus?
I ask because there will be a dissolved oxygen gradient in the media and once you hit a critical mass of cells at the bottom of the tube, diffusion of dissolved oxygen to the bottom will be growth rate-limiting. Some bacteria will form a pellicle biofilm at the surface or attach to the meniscus where significantly more oxygen is available, but the growth dynamics of these will not be the typical exponential growth of shaking broth cultures.
Do you have any way to keep the cells suspended or the tube moving? Even adding a nutator/rocker to the incubator would probably improve recovery.
if using screw capped tubes change to regular test tubes closed with cotton plugs, might improve the yield and you could increase the broth volume as the dissolved oxygen available for the inoculum size itself might be disproportionate.
Yes it can. If the heated air is not equally distributed within the microenvironment, it may affect the growth of aerobic microorganism. For the optimal growth of aerobic bacterias, the incubation period must be 37⁰c for 24hours and the provide an adequate oxygen for it proper growth.
For optimal result,
Check for the regular calibration and monitoring of the gravity convection incubator to ensure uniform distribution of temperature, Oxygen level and humidity.
I hope this would help
Alexander C. Anderson
The classic growth: turbidity in the whole tube, nothing different at the top nor the bottom and mixing does not cause any change.
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