Hello everyone. I have tried to test lactic acide bacteria for their co ggergtion ability with E.coli but I'm having problems.I have to read the DO at t=0 and after 1h of incubation. But after I incubate The DO increses and as a result I get a negative value. What could be the reson behind it and Is their any protocole you can share with me that will help me get a positive DO.
Hi,
This method is inaccurate in calculating the numbers or effect of bacteria.
@Alaa Kareem Niamah. Can you please explain to me why is it inaccurate.
What the blank solution do you use as a zero reference? you have to make sure that before analyzing the sample, you have to press the autozero.
Co-aggregation can be determined based on the decrease in absorbance value between the mixed culture and the single culture. Regarding co-aggregation between lactic acid bacteria and pathogenic bacteria, it is expected to have a decrease value of absorbance, which means having a high percentage of co-aggregation.
@fenny mahara thank you for responding, yes i make PBS before analyzing.
Negative absorbance also may happen due to the problem of the instrumen calibration. You should use uninoculated sterile media to blank the machine by setting it to 0 absorbance (by pressing autozero). It will standardize the turbidity of the media without any cells in it.
So, what I try to explain is if you have a problem with the negative DO, you have to check the instrument calibration. But if you mean that the negative value refers to the co-aggregation value, it means that there is no decrease in population after mixing lactic acid bacteria with pathogenic bacteria. It indicates that the mixture has a positive interaction, which means that LAB can't inhibit the growth of pathogenic bacteria. CMIIW.
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