SOORY, I WORK ABOUT, SINCERILY , CLAUDETE

Contar este tipo de colonias que se ramifican y expanden por el agar es compleo en el sistema UFC. Yo te recomiendo hacer conteos por Numero mas probable y con tres repeticiones, este método no usa colonias asi facilita el trabajo 

Dear Barbara,

My understanding of your question is a little different and I have provided three different answers that may be of help.

Interpretation of viable cell numbers. If you are trying to count viable bacterial numbers using plate based assays, then there is very little you can interpret from a single large colony on one plate - this might be a very fast growing and spreading strain originating from a single cell, or it might be several small colonies overlapping, each coming from a different cell. If you had plates a series of dilutions you could look at the higher and lower dilution plates to work out how many viable bacterial counts there probably are, but if you only have one plate and one colony then you are stuck.

Varied phenotypes. Bacteria can produce a wide range of colony phenotypes, and it can be a surprise to find that a strain you are familiar with produces different-looking colonies on different types of media. Some media (especially the agar concentration) will permit some level of swimming on the surface, or twitching or swarming, and these motility mechanisms as well as simply cell pushing in colony growth can effect colony diameters and regularity (e.g. swarming often produces multiple tendrils). We tend to look at environmental pseudomonads on dry, 1.5% w/v agar using King's B medium. If we increase the agar concentration, colonies get a lot smaller. Reducing the agar concentration down to 1% allows twitching, and between 1-0.5% swarming can occur on fresh (wet) plates, and between 0.3 - 0.4% swimming on the surface occurs.

Bacterial aggregations. Finally, it seems to me that people often confuse biofilms with colonies. Some of the early biofilm reviews have suggested that colonies are intact biofilms, but I would argue that biofilms (e.g. in flow cells) and colonies (on agar plates) are two examples of the larger continuum of bacterial aggregations. If you add water to a colony, you might get a slime, if you dry out an submerged surface biofilm it starts to look like a colony (we have just submitted a book chapter manuscript about this - if you want a copy of the draft please let me know) - so I think that worrying about whether the large aggregation you have on your plate is a colony or a biofilm is a little pointless: both can be initiated by a single viable bacterial cell, both can grow at different rates, and both can combine with nearby biofilms or colonies to produce a single massive growth.

Regards, Andrew.

Daniel Toro,

We have to use that method, I´m studying methods to be implemented in a beverage industry. Do you know, how can i do that using pour plate methods? Maybe if I modify the medium composition?

Regards

Dear Andrew,

Is exactly as you understood. And it is the first answer that I wanted to know. Well, without doing another test, NMP as suggested by Daniel...i think I don´t have a way to know the CFU. The problem is, that this are routine tests and I can´t re-do the tests. I need to know as soon as possible the results. It is difficult to implement new tests as routine, as this "strange growth" only appears from time to time. I think that maybe I am truly stuck.

Regards,

Bárbara

My dear friend:  There is heaven and earth difference in biofilm and a large colony of a single bacterium (through biofilms are also colonies). Normally biofilms would stain differently from a normal bacterial colony and would appear totally different under the microscope from a colony. 

Jai,

My doubt is not if is it a biofilm. I can´t tell if the growth in the PCA plate is one colony that spread troughout the plate or if the colonies grew together to appear as one colony..

I would suspect both, because many species of Bacillus (especiallyB. cereus) gives such ramified growth which some time spread all over the plate whereas B. megaterium forms definite shaped colonies and might unite to cover the whole plate.