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Bio-Chemical Tests Used in Identification of Microorganisms.
In various pharmaceutical manufacturing plants and in medical field, biochemical tests are performed to identify microorganisms.
Such biochemical test helps in differentiating bacteria and thus is a way to diagnose the cause of infections and other disease related to micro-organisms. This test indicates different characteristics of microorganism with respect to subjected bio-chemicals and thus helps in their identification up to species level.
Once this identification is done, specific recommendations/corrective actions are implemented for treatments and further resolution of microbial infection or contamination.
Bio-chemical test includes Catalase test, Carbohydrate oxidation fermentation tests, MR-VP test, Simmon’s citrate test, Nitrogen metabolism – urea Hydrolysis test etc.
These tests are done under aseptic conditions under totally controlled environments. This is to avoid un-wanted contamination and to keep the validity of test.
In catalase test, oxygen is used as final electron acceptor by many micro-organisms the breakdown of H2O2 into water and oxygen molecules is characterized by bubble formation and this indicates the result as Positive (+). Eg. Staphyloccocus aureus.
In Carbohydrate fermentation test, acid and gases production are detected. Acid production is indicated with color change and it shows that microorganism under test are capable of utilizing various carbohydrates.
MRVP test, which is abbreviation of Methyl Red Voges Proskauer is test to know if organic acid is produced, the positive result is just a no change in color of MR chemical indicator.
Simmon’s citrate test is to identify the ability of bacteria to ferment citrate. In this test when citric acid or sodium citrate is in solution, it loses sodium ion to form citrate ion. This Citrate is break down to pyruvate. When a bacterium uses Citrate, medium turns alkaline.
Another test which is employed in identification of microorganism is Urea test. In this test, Urease breaks down urea into ammonia and carbon dioxide.
Bio-chemical test is fundamental concept in microbiology which helps in identification of micro-organism of interest out of hundreds of samples.
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Extremophiles and detection techniques

Modern biotechnology techniques and biochemical detection methods including restriction fragment length polymorphism (RFLP), polymerase chain reaction (PCR), rRNA sequence analysis and sensitive colorimetric methods are improving bacterial detection and enabling better distinction of bacterial species.

Extremophiles are organisms that withstand and thrive in extreme conditions such as extreme heat or highly acidic conditions. Most extremophiles are microbes. An example would be the Thermus aquaticus bacteria which survive in hot springs and from which Taq polymerase is extracted for polymerase chain reaction (PCR). Another extremophile is the microorganism HSL10. This was identified as a member of the genus Microbacterium by morphological observation, Gram staining and sequence analysis of the 16S rRNA gene and the 16S-23S rRNA intergenic spacer region Microbacteria are a genus of bacteria in the family Microbacteriaceae, which have been isolated from both environmental and clinical sources. Like other extremophiles, HSL10 has been identified as a potential source of enzymes such as alkaline protease. It has been confirmed to be capable of secreting alkaline proteases; this capacity was increased by both NaCl and yeast extract. In order to sensitively detect protease production by HSL10 under neutral and alkaline conditions, a sensitive colorimetric method was developed by using the classical Bradford reagent for substrate staining to improve the contrast between the hydrolyzation zone and the substrate background on agar plates. The isolation and characterization of HSL10 has both academic and commercial importance and viable detection techniques play an important role in exploiting this and other microorganisms.


FUNKE, G., FALSEN, E. and BARREAU, C., 1995. Primary identification of Microbacterium spp. encountered in clinical specimens as CDC Coryneform Group A-4 and A-5 Bacteria. Journal of Clinical Microbiology, 33(1), pp. 188–192

LÜ, J. et al., 2013. An extremophile Microbacterium strain and its protease production under alkaline conditions. Journal of Basic Microbiology; Date of Electronic Publication: 2013 May 17
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