When looking at various stains (i.e gram , acid fast), how do you differentiate between Micrococcus roseus and Lactococcus lactis?
Thank you
Both strains have the same staining results. So how would you differentiate by appearance?
I am not a microbiologist, just trying to suggest hints to differentiate, not identify.
They are both gram positive, but if you examine the physical appearance, M.roseus tend to be in tetrads, while L.lactis are in pairs. They seem to be quite distinctive in appearance, even though their sizes are similar.
See them for yourself in enlarged pictures at:
http://en.wikipedia.org/wiki/Micrococcus
http://en.wikipedia.org/wiki/Lactococcus_lactis
To differentiate between Micrococcus roseus and Lactococcus lactis, you can follow these steps:
1. Observe the Gram stain: Perform a Gram stain on the stained material. Both Micrococcus roseus and Lactococcus lactis are Gram-positive bacteria, appearing purple or dark blue after staining.
2. Look for cell arrangement: After the Gram stain, observe the bacterial cell arrangement under a microscope. Micrococcus roseus typically occurs as single cocci (spherical shape), whereas Lactococcus lactis usually forms short chains or pairs of cocci.
3. Conduct a catalase test: To further differentiate between the two bacteria, perform a catalase test. Micrococcus roseus is catalase-positive, meaning it produces the enzyme catalase, which generates bubbles of oxygen when hydrogen peroxide is added. Lactococcus lactis, on the other hand, is catalase-negative, so no bubbles will be produced during the test.
4. Perform an Oxidase test (optional): If necessary, you can also conduct an oxidase test to aid in differentiation. Micrococcus roseus is oxidase-negative, meaning it does not produce the enzyme cytochrome c oxidase, while Lactococcus lactis is also oxidase-negative.
By following these steps, you can observe the Gram stain, cell arrangement, and perform catalase and potentially an oxidase test to differentiate between Micrococcus roseus and Lactococcus lactis.