I have got two different sized colonies in a plate of Salmonella Paratyphi, identified by biochemical methods. What does two different sized colonies mean? What kind of question can I investigate in this regard?

Protocol followed:

Positivity of serum sample was checked in BacT/Alert blood culture system. Bacteria was subcultured from the positive result giving culture bottle from the BacT/Alert system and incubated overnight at 35 degree celsius. Two different sized colonies were found and they were subjected to biochemical and antisera tests and both identified as Salmonella Paratyphi.

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    $\begingroup$ Could you please add details about the protocol you followed ? $\endgroup$ – MauroM Oct 27 '15 at 11:29
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    $\begingroup$ @MauroM Some details added $\endgroup$ – Ahmed Abdullah Oct 29 '15 at 5:37
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    $\begingroup$ Do you happen to have an image of your plate? $\endgroup$ – Chris Oct 29 '15 at 8:34
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    $\begingroup$ Thanks @AhmedAbdullah ! Unfortunately i'm not expert enough to solve your doubts; the only thing that i can think is that the founders of the two colonies reacted to the culture environment differently e.g. the founder of the bigger colony was more rapid to adapt and divided more rapidly compared to the other... I would try to made another culture (exactly same conditions) to see if the size difference persists and then investigate the genomes of the two colonies even if i'm not sure wich technique to use since i'm not a microbiology expert. $\endgroup$ – MauroM Oct 29 '15 at 8:41
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    $\begingroup$ @MauroM thanks for you suggestion. I'll try along this line. $\endgroup$ – Ahmed Abdullah Oct 29 '15 at 8:59