Which bacteria look similar to E coli under 100X optical microscope? In a E coli fermentation culture, which contaminants look like E coli? How can we distinguish them?
Its hard to tell exactly which contaminants is present but according to my experience in the case of contamination it should be Bacillus species bacteria. You must be wondering about it will be very easy for differentiating bacillus from E. coli due to differences in its gram staining and cell shape but some bacillus species are gram variable and are often mistaken as E. coli in the way they appear in the microscope.
The shape that appears in the microscope also differs on how old culture (days of incubation) are you observing. In my view the contaminants may be Bacillus licheniformis or geobacillus. They are the most probable ones.
I hope this helps
In general, microscopy is not suitable for differentiating bacteria. Even if you do a Gram-stain, there is now way to identify bacteria to the species level.
To answer your questions:
Which bacteria look similar to E coli under 100X optical microscope? Many bacteria look like E. coli when examined under the microscope (if not stained Enterobacteriaceae, Bacillus, cornyeforme bacteria, they all appear like rods, although the shape differs).
(…) which contaminants look like E coli? How can we distinguish them? Gram stain allows you to classify into Gram-negative rods (which includes E. coli) and Gram-positive rods (which include Bacillus, Corynebacterium, and some others). The experienced microbiologist may make an educated guess (i.e. looks like Enterobacteriaceae, which again includes E. coli but also dozens of other closely related taxa). [Whether or not these are typical contaminants in your specific setting is another questions.] For a definite answer you need to culture an aliquot to see, what’s going on. With the bacteria grown on solid media, you can go for identification (by biochemistry, MALDI-ToF or DNA sequencing). In general, culture of an aliquot on solid media can be used as purity control.
Hope I got your question well and the answer is helpful for you.
There are many groups of bacteria that look Gram-negative rods. If your facilities are not abundant in materials, the cheapest way to further identify them would be to grow on MacConkey agar overnight, and identify the colours of the morphology. Also, motility test in simple broth for 2 hours. If you have some API strips, you can use one of the API 20E.
It is not easy to say, but you can see many rod bacteria similar to the Escherichia coli !
- Badges
- Science topic
- Similar topics
- Biological Science
- Biochemistry
- Biomolecules
- Peptides