we were doing experiment to check the effect of salt on E-coli some plates shows small number of colonies with small size
The principle and concept of Osmosis and osmotic pressure will guide you on it
It may also be stress. When I was working with xenobiotics, after the addition of a certain chemical compound the cells sometimes grew smaller than they normally looked like. But that happened only in the presence of some xenobiotics which bioremediation I tested.
it also happens with my reseach. When measure the antagonistic activity of Bacillus to different pathogen, the colony size varies significantly confronted with pathogens. If the size of the colony has an impact on your experimental results, you have to find a way to avoid it. like evalue the OD600 to a certain number. Actually this happens when Bacillus was growing under stress, yet if it matters depend on your propose.
Regards
Bing
stress conditions reduce the growth rate of the bacteria. and high salinity result osmotic pressure and water flows outside of the cell and cells tend to shrink.Thats why when preparing culture media we add proper amount of salt to acheive optimum growth. requirement of salt will vary from bacteria to bacteria and some bacteria may evolve to be resistant to high level of salt conditions.
colony size reduce means somehow its growth rate was hampered. In your experiment you r use salt but salt has a negative effect on E.coli.It dis regulate the osmotic balance of this bacterial cell after tolerance concentration may be this is the main reason of smaller colony size.
The salt could affect bacterial multiplication/ growth. Check also the incubation temperature
Just to avoid some very simple experimental misinterpretation, it recomend to standardization of colonies growing: over agar surface, over a membrane, or inside agar (pour plate). In this case, besides osmotic pressure it will important to consider aerobic condition (limitation to Oxigen molecules).
Might be due to environmental pressure and shock.I think it is sort of physiological and anatomical change sometimes temporarily occurs as struggle for survival.
Some concentrations of salts produce stress in bacteria and this affects the shape and growth of the bacteria. Osmotic shock affects cell wall synthesis and membrane. Also pay attention in the culture medium that you are using because sometimes it´s difficult to recover bacteria that have been stressed
Hey
Are you experimenting with salt (sodium chloride) or other salts (copper sulphate, potassium hydroxide...)?
Different salts will cause different results. Sodium chloride will increase the osmotic pressure, and only the cells that can adapt to the stress will grow. KOH will alkalinize the media, so only the bacteria adapted to a higher pH will survive and form colonies. If in the other hand you're using copper sulphate, you'll have an oxidizing environment, and cells will once again need to adapt. Only cells that are adapted will grow and form colony. Always there is a stress in the environment, only the fittest will survive, and thats only a small fraction of the initial population. In stress conditions, cells will grow less since they have first to overcome the stressing agent - so you'll get colonies with much smaller size. It's perfectly normal.
Salt at certain concentrations can be stressful to cells due to osmatic shock as suggested by others. It could also suggest that small colonies are mutants that are not able to handle the stress, if you have both large as well as small colonies on your plates.
What type of media are you using? if it is minimal medium, then small colonies suggest they are adopting to the condition and they are mutants that can handle the condition if they are the only colonies.
All the best
Different salt conc. affects osmotic pressure, pH and thus affect the growth of bacteria. Different growth rate leads to different size of bacteria
I assume you are using spread plate and not pour plate. Colonies in nutrient agar are always football shape. I assume you are testing pure NaCl. Which bacterium are you testing. 2.5% NaCl is inhibitory to most bacteria. However Staphylococcus aureus will grow in the presence of 15% NaCl. Colonies in close proximity of one another are smaller.
Salt will affect the normal growth of E. coli. Osmotic shock is capable of affecting the bacterium. In response to such stress they may produce smaller colonies. Why did you add salt to your growth medium? Are you experimenting on the effect of salt on the organism? It is important to know why you are conducting the experiment.
If you are using different concentrations of the salt (any), you may find smaller colonies /less growth/less number of colonies at higher concentrations. This is normal with mesophilic bacteria.
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