Classification of Bacteria

This simply means the study of bacteria. Bacteria are small unicellular microorganism that can only be seen with the aid of microscope. Bacteria exist in a different form, such as cluster, ovoid, spheroid, etc. they poses a sling capsule, cell wall, cell membrane, and dense cytoplasmic granule with nucleus composed of DNA and RNA.

Bacteria are group into two categories: I.e.

  • Base on the use of oxygen which they bacteria require for existence.
  • On the bases of their morphological shape, for more detail on the classification base on the use of oxygen see cultivation of bacteria.

Classification of bacteria base on the morphological basis is as follow;

Cocci: this are type of bacteria which are circular in shape, some are bond together to form chains like structure, those are called streptococci, i.e. sore throat bacteria, while some are compound in a bunch of cluster those one are called staphylococcus i.e. boil bacteria, hence some other are stick together in peer called diplococci, i.e. causative agent of pneumonia, while bacteria that occur in a four group are called tetrads.

Oviod or Speriod Coccus: the rod or cylindrical i.e. bacillus, the curved shape i.e.vibrio, the spiral shaped i.e. spirally, and the coil shape is spirochetes.

Coccus is plural of cocci, have a size of 0.5-1.0 micromter in diameter, cocci have a general axis approximately the same that of other axis of bacteria.

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Some of the cell are sometime flattened, the flattened yield a kidney shape like cells or it disfigure the shape away from spherical that yield streptococci. Bacteria reproduces by binary fission, in this case if any the daughter cells refused to dissociate from   the parent cells, but separate from fission where the division take place before another fission take place, these are called diplococci.

But if fission take place when remain attached or bond to it parent causing the organism in this case form a chain of cocci, this is called streptococci. But a situation where by a divion is not in one direction, which result in forming a random clump of cocci, these are called staphylococci. Sometime these cocci remain in two pair for one further division to take place, in this case they form a regular aggregate of four cocci, and this is called tetracocci. While sometime the cocci may remain for one further division to take place at the right angle of the previous side in these case give rise to a cubical packed of eight cocci, these are called sarcinae.

NB: the word staphylococci, streptococci, and sarcina are used as a name for the whole class of the organism.

Bacilli: these bacteria are rod-like in shapes some of them have flagella which they used for their movement i.e. causative agent of typhoid fever. Bacillus is the plural of bacilli their size ranging from 1-10 micrommeter in length and 0.3-1.0micrometer in width, bacilli form non grouping compare to that of cocci that yield different starter of generic base on their clustering. But they form pair and chains which either be diplobacilli or streptobacilli. Sometime after fission some rod form in some position in such a way that the daughter cells remain attached to the parent cell, but some may swing away to different angle in this case they yield some complex appearance shapes; some form characteristic of cyanobacterium sometime of cuneiform bundle which is the characteristics form of mycobacterium.

Under unfavorable condition, some bacteria under these change result in the formation of spore. There is certain place in the cell which the nuclear material is concentrated. With the recent improvement that takes place in the bacilli are the leisure stages at which the bacilli rest.


Growth cannot take place in this stage, because the area is unfavorable for organism, but the spore remain stagnant until it restore a favorable condition before growth will take place. The spore mature membrane confer a resistance to staining, sun light and heat, despite these condition which the spore found itself dos not make it loose it capability of germination, i.e. general enlargement of the spore, these give bacillary the power to yield spore membrane.

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Condition of the spore give morphological diagnosis of the organism, some of the spore exist at the end of axis of the bacilli without reducing force of the bacilli cells, while others occurs on the center or towards the end of it shape.

Spirillum: this are twisted bacteria. They use flagella as their locomotive organelles i.e. sphilla bacteria spirillum the plural of it is spirillum, it have dimensional size approximately 4 x 10 micrometer. They are rods with helical in shape, they are gram-negative organism.

Vibrio: these are curved in shape, they appear just like comma, i.e. cholera bacteria. The plural of vibrio is vibrio’s. They are with size of 4×0.5 micrometer, they are short, curved rod shaped rather like a comma, they also move by means of flagellum and generally gram-negative.

Spirochete: their body is twisted in a helical shape, they have length approximately 10-20 micrometer and thickness of their body is 0.2-0.4micrometer. There are several variety numbers spiral, their numbers varies with their species, and they also have moveable organelles, which serves as their mobile vehicle. The spiral is very complicated in absorbing aniline dye stain before best result can be achieved, impregnating the species with silver method impregnation.

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