Dear Samer

Even though you do not have carbon source or bacterial growth, bacteria died and "born" again. The new bacteria will grow on the carbon released by dead bacteria. So no bacterial growth does not mean that bacteria are dead or static. From that, we could think living bacteria are producing compounds to cope with this situation, like a "biofilm". From my experience, turbidity can increase even though the bacterial growth decrease or is null.

Now it is also important to know how do you measure growth? By CO2 release, by CFU counting or counting with fluorescence microscopy. With CO2 or CFU, you measure the living bacteria. By fluorescence microscopy, you count all the bacteria even the dead one.

I hope this could help

Best regards

Geoffrey

Dear Samer

Even though you do not have carbon source or bacterial growth, bacteria died and "born" again. The new bacteria will grow on the carbon released by dead bacteria. So no bacterial growth does not mean that bacteria are dead or static. From that, we could think living bacteria are producing compounds to cope with this situation, like a "biofilm". From my experience, turbidity can increase even though the bacterial growth decrease or is null.

Now it is also important to know how do you measure growth? By CO2 release, by CFU counting or counting with fluorescence microscopy. With CO2 or CFU, you measure the living bacteria. By fluorescence microscopy, you count all the bacteria even the dead one.

I hope this could help

Best regards

Geoffrey

-You have aerobic conditions? If so, agitation plays an important role to the floc destruction.

-Bacteria need time for acclimatization. If food is too much (and other causes) bacteria may be socked. If bacteria are socked a lag period is observed and when growth begins, dispersed bacteria (no flocs formed) cause turbidity.

You can see the life using light microscopy.

In your question it is not clear in which conditions did you measure you turbidity.

Turbidity by definition means how much the light is scattered by particles in the sample. Classically in microbiology it is used to to estimate the change of the number of particles (all the OD optical density measurements are actually all about measuring turbidity).

The turbidity or ligth scattering depends also from the properties of the particle (this principle is exploited in flowcytometry). So perhaps some parameters of your bacteria are changing (cells shrink or get bigger if you change osmotic pressure) which cause different light scattering. Another option is that when you have filamented cells then after division (it might not need much carbon) also the ligth scattering properties of your sample might change (at least in theory).

By following it using HPLC, the peak area doesn't decrease with time.

In your case, the carbon source could be the bacteria itself?

Yes indeed .. it is what we call 'cryptic growth', the new bacteria is living on the organic carbone released in the medium by the dead bacteria

If you have pradator bacteria, especially rotifers or metazoa you have 'cryptic growth' phenomenon. Also, very low F/M.