Dear Ima Ghaeli,

Thanks for your question. Maybe the following is of help.

1)      Cell numbers. A surface in contact with a liquid containing biodegradable nutrients and microorganisms will in general lead to growth of microorganisms on the surfaces and in the liquid. Detachment of (lumps of biofilm) cells from the biofilm into the liquid may occur, affecting the number of microbial cells in the liquid. So, it is a bit how planktonic growth is defined. The increase in the total number of cells in the liquid could be increased due to detachment from the biofilm.

2)      Growth of cells in a biofilm may affect conditions for microbial growth, such as (local) changes in oxygen/nutrient concentration, pH, which possibly may reduce the total or rate of growth of microbial cells in the liquid.

Hypothesized is that two counteracting affects may occur. An increase in liquid cell number by detachment from the biofilm, and a decline in liquid total cell number by the biofilm growth affecting growth conditions negatively.

Best regards, Hans

Please see the graph attached. It is Klebsiella pneumoniae strain ATCC4352 that was cultured in poor medum (10% TSB + 90% saline) or in standard TSB medium. Every 24 hours the sample of planktonic forms and biofilmic forms were taken and cultured quantitatively. As You can see biofilmic and planktonic cells  interact between themselves and compete for nutrients and oxygen just as Prof. Vrouwenvelder wrote before ...

Dear Dr. Adam,

Thank you for your reply,

As shown in the graph, the growth of bacteria in the biofilm at everytime (for both poor and standard medium) is higher than that of planktonic cells. 

In fact, I would like to compare the growth of biofilm and planktonic cells for the same bacterial strain (same initial concentration), in the same medium under the same conditions, but different substrates. Is it possible to anticipate the extent of surface resistance to bacteria, just with comparing the planktonic cells number at every time point? e.g.,the higher planktonic cell number (after 24 hours), the more loosely-bound biofilms to the substrates, illustrating the more substrate resistance to the biofilm formation?

Ima

Dear Irma,

Some considerations:

Quantify biofilm growth: When the flask after 24 h growth is emptied, assess the total amount of biofilm that developed. When the total biofilm amount is minute compared to the total biomass amount in the liquid, then the role of the biofilm may be neglected.

Maybe when you pour the growth media into an empty clean flask after each 6 hours, the bacterial growth in the liquid may be less affected by the biofilm growth in the replaced flasks than using the same flask for 24 h. Comparison of flask and no flask replacement may give some idea to what extent the growth is affected by the biofilm growth.

Another or an additional approach may be to do a particle size distribution measurement. When biofilm detachment occurs, than larger sized particles are expected.

Slower mixing of the flask may reduce the detachment of cells and cells clusters from the biofilm. However, because of slower mixing also gradients or e.g. oxygen may occur, hampering the microbial growth in both the liquid and water.

Best regards, Hans    

Dear professor Vrouwenvelder, 

Many thanks for your kind reply,

I will consider the approaches for my work.

Best regards,

Ima