Gravity incubators rely on natural convection for heat distribution. There is no fan or blower system, and the heat rises from the heating element at the bottom of the incubator.



I'm working on a strict aerobic bacteria. I have a problem with the growth rate of broth cultures; the growth seems too light in comparison to the inoculum size (4-5 colonies), low broth volume (4-5ml), and incubation conditions (24 hrs). The incubator available to me is of the type gravity convection incubator with no mean of shaking. I use screw cap test tubes for the broth cultures, the degree of tightness of the caps greatly affects the produced turbidity. However, even after learning about this and making sure the caps are loosened, the growth rate is increased but still inadequate.

I have a colleague that has access to a fan-forced incubator and they seem to have a higher growth rate.


Can Gravity convection incubators negatively affect the growth of strict aerobic bacteria?

Prior work

I have not found any text on the internet that discusses this matter. I have great experience in searching.

  • 1
    $\begingroup$ Can you update the question to include details about shaking? $\endgroup$
    – Michael_A
    Dec 4, 2023 at 23:31
  • $\begingroup$ Done (mentioned that no shaking incubator was used, as it is not available) $\endgroup$ Dec 5, 2023 at 15:11
  • $\begingroup$ Hard to make a definitive answer without more information. I would confirm the temperature where your cultures are growing in the incubator with a thermometer. Flasks are generally better than tubes for gas exchange, but not sure if that applies to static cultures. Pre-warming the media can help. And best practice is to inoculate from a single colony whenever possible. Even minor genetic variations between colonies can result in competition between two or more clonal lineages, slowing outgrowth during the lag phase. $\endgroup$
    – MikeyC
    Dec 5, 2023 at 15:31
  • $\begingroup$ I used to do single colonies before afriend suggested doing more. I don't intend by using definite values in some of the givens I mentioned to build a complete scientific picture, all I need is the effect of using gravity convection incubators on the growth of broth cultures of aerobes, from practical experience. $\endgroup$ Dec 6, 2023 at 22:05


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