I grew Bacillus in minimal salt media (composition below) and exposed it with chromate at concentration 1, 5 and 10 ppm. Then, I made growth curve of each Bacillus isolates. But unfortunately, I got bad growth curve. Instead of showed each of growth phase, it didn't showed clear growth phase and relatively seemed like no growth (the OD showed ups and downs during the time I measured it). Anyone can explain me why was that happen?
composition of minimal salt media
Solution A
K2PO4 0,3%
Na2HPO4 0,6%
NH4Cl 0,2%
NaCl 0,5%
DI water 80ml
Solution B
glucose 5%
MgSO4.7H2O 0,05%
DI water 20 ml
Dear Prima,
How long (in hours) did you observe the growth (fig shows only 4.5 on x-axis, whats the unit?). Also what was the final concentration of glucose in the medium?.
In my opinion your strain did not grow well (O.D. is negligible). Variation in O.D. can happen due to - i) low or limited growth, ii) cloudy media (due to MgSO4), iii) error in handling spectrophotometer.
The given media composition looks OK, if u use 0.5% glucose and prepare media carefully (minimal whiteness due to MgSO4) and use 0.1% inoculum (Bacillus culture) the O.D. at 600 nm would provide you with a nearly sigmoidal curve over a period of 24 hours.
I hope this would be of help.
Regards
Prasun
What are you doing? Minimal medium are not used for just any study except for specific studies e.g understanding gene transfer in bacteria such as conjugation, transformation etc. Until you state what you want to do, I may not be able to answer your question correctly. Again, take note that it is neither the pH nor temperature that is affecting your your optical densities but the make up of the minimal medium because the organism exhaust the little major growth factor quickly and immediately growth rate will decline. Kindly state specifically what you are doing and I may be able to provide help. Best wishes.
Thomas: I wanted to know the growth pattern of my isolates when they were exposed by chromate. I used minimal media since when I used nutrient broth chromate seemed like to made complexation with protein contained in nutrient broth.
Kumar: It was 4,5 hours for OD measurement and glucose final concentration was 5%. I didn't find cloudy-media during media preparation. I think the problem is on my Bacillus strains, since I also work with Enterobacter and the growth pattern was fine. All of Bacillus strain showed the same growth pattern.
All: thank you for your response.
Adisya,
Some Bacillus strains forms aggregates, in our case we have been working with B. amyloliquefaciens and sometimes that happen. You have to mix really well for enough time on vortex each of your samples to destroy those aggregates.
I Hope this can help you.
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