Question

In microbiology, many different species of bacteria may have the same shape – rods, spheres, or spirals. Using the Internet as an information source, list some criteria that microbiologists can use to key out microorganisms that may have the same physical appearance.

Answer 1

Ans:

In the question it has been asked if the orgnism have similar shapes such as rods, spheres or spirals, what could be other criteria to distingush this similar shaped microbes;

Microorganisms have various morphological features. In order to identify microbes one need to carryout detailed characterization of microbe. This characterization includes shape (morphological shape), size, appearance, colony characteristic, motility, gram character (gram positive or negative), present or absence of endospore, capsule and finally genome sequence.

Even if the microorganism is similar in shape, there may be difference in motility one may be motile and othe rod may be non motile.

Similar to this the same shape organism may have different gram character and this can be explroed further by performing gram staining methods (i.e. by staining microbes with crystal violet and saffaranine). In this staining the gram positive organism will be stained by crystal violet, whereas negative organism will be stained by saffaranine.

Other criteria is presence of endospore. This can be elucidated by following Schaeffer–Fulton staining protocol which will help us know or differetiate same morphological organism on basis of endospore presence.

Further more we can do capsule staining by using 1% crystal violet.

The final discrimination of microbes can be possible by biochemical and molecular approach. In biochemical approach the various test like IMViC (Indole, Methylred, Voges-Proskauer and Citrate test) carbohydrate utilization assays are carried out.

In molecular approach the 16S rRNA of the microbe is amplified, cloned in a sequencing vector like TOPO10 or 4 and it is subjected to DNA sequencing. The sequence thus obtained is then subjected to BLAST to find the exact identity of similarly looking microbes. The 16S rRNA sequence can also be used to construct phylogenetic tree to know the phylogenetic relatedness of the microbe under study or investigation.