There are many billions of microorganisms like bacteria, fungus, viruses on earth’s crust.  Some bacteria have few common characteristics but mostly they are different in some aspects (Morphology, mode of nutrition, etc). 

It becomes a big problem for taxonomists to understand each bacteria. Therefore they classify into different groups and subgroups.

Here is the Classification of bacteria chart.

Classification of the bacteria flow chart

Classification of bacteria into two main groups on the base of gram stain. Bacteria that attain violet color is called Gram-Positive Bacteria. While red color bacteria are Gram-negative. Here we classified bacteria in chart form. There are two main categories. 

On the basis of gram stains, they are further classified as Cocci and Bacilli. Cocci or ball shape bacteria further classify  Staphylococcus and another one is Streptococcus on the base of the Catalase test.   Staph bacteria show catalase positive while Streptococcus shows catalase-negative.

Staphylococci are further classified into two more types. Staph Aureus on Coagulase test shows positive result. Staph Epidermis shows Novobiocin sensitivity while Staph Saprophytic shows resistance to Novobiocin.

Streptococcus classification flow Chart microbiology

The following steps are for the taxonomy of streptococcus in microbiology.

  1. You first neend to perform Gram stain of slid. Identify the gram positive or gram bacteria. If gram postive bacteria identified,you further need to identify the whether they are cocci or rod form.
  2. After gram positive cocci identification,your next step is catalase test. If catalase test is positive,it means pathogens are staph otherwise they are streptococcus. you need following steps next.
  3. After identificaton of streptococcus, you need to perform hemolysis test. now look into the hemolysis around the colony.
    1. You will see either alpha, beta or gamma hemolysis. Alpha hemolysis occure in Strept Pneumonia and strept Mutan. Beta hemolysis occure in strept Pyogenes and aglectecia. While gamma or NO HEMOLYSIS occure in enterococci, e. fecalis, peptostreptococcus.
    2. After the identification of alpha, beta or gamma hemalysis, now you will run senstivity test. Optochin senstivity test for ALPHA hemolysis bacteria while, bacitracine senstivity test run for beta hemolysis bacteria.

S. Pneumonia and S. Viridin show alpha (Partial Hemolysis), S. Pyogenes, and S.

Aglectiae shows Beta Hemolysis (Complete Hemolysis) while Enterococcus shows Gamma Hemolysis or (No hemolysis).

Staphylococcus classification flow chart

Following steps are performed for the final identification of staphylococci.

  1. Gram stain performed, identify the gram positive or gram bacteria. If gram postive identified, further identify the cocci or rod form of bacteria.
  2. After gram positive cocci identification, catalase test performed. If catalase test is positive,it means pathogens are staph otherwise they are streptococcus. you need following steps next.
  3. After identificaton of staphlococcus, you need to perform Coagulase test.
  4. If coagulase test is positive, pathogen is staph aureus. But if this test is negative, you to perform senstivity test.
  5. In case of coagulase negative test, antibiotic senstivity test run. You need to place Novabiocin antibiotic on inoculated plate of staph.
    • Now if you see senstivity to novabiocin, pathogen is staph epidermidis . But if there is resistance to novabiocin then it will be staph saprophyticus.

MCQs From Gram-Positive bacteria

1). Which Bacteria show Catalase +ve?
A. Stept coccus B. Staph coccus
2). S. Aureus and S. Saprophytic we are #distunguish by ……test?
A. catalase B. coagulate
3).Bacteria show Novobiocin_Senstive?
A. S. Saprophytic B. S. epidermis
4). Chose bacteria show #B_Hemolusis?
A. S. Pyogenes B. S. enterococcus
5) Gamma Hemolysis mean
A. Complete Hemolysis B. Incomplete hemolysis C. No Hemolysis
6). Streptococcus show Alphs Hemolysis?
A. Viridin B. Pyogenes

Answer key:1. b,    2,b   3, b    4, a   5. c     6,

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