Basic concepts on morphological classification of bacteria

1. BACTERIA & MORPHOLOGICAL
CLASSIFICATION OF BACTERIA
rambahadurkhadka00@gmail.com

2. Definition
Bacteria are single-celled and are classified under the
domain Prokaryota. As such, they lack membrane-bound
organelles like those found in eukaryotes.
Although they are all microscopic organisms that can be
found in various environments in nature, bacteria widely vary in
size, shape, and arrangement.

4. Bacterial Size
In general, bacteria are between 0.2 and 2.0 um - the average size of most
bacteria. Research studies have shown their size to play an important role in
survival over time.
In bacteriology, the micron (micrometer) is the primary unit of
measurement: I micrometer (um) is one-thousandth of a millimeter.
* Given that the limit of resolution for a human eye (naked eye) is between
100 and 200 um (about the diameter of a human hair) then the majority of
bacteria cannot be seen with the naked eye.

5. The following are different sizes of bacteria:
Smallest Bacteria
Some examples of these bacteria include Mycoplasmas (about 0.25um),
Haemophilus influenzae which ranges between 0.2 and 0.3um and
Mycoplasma gallicepticum which range between 200 and 300 nanometers
in diameter.
Large Bacteria
Some bacteria are large enough to see with the naked eye. For instance,
whereas Schaudinnum bütschlii that measure between 4 and 5um in
diameter are considered to be large bacteria,
Thiomargarita namibiensis may grow to be as large as 0.75mm in diameter.
This makes them some of the largest bacteria ever discovered. As such,
they can be seen with the naked eye - when they reach such sizes.

6. Shape and Arrangement (MORPHOLOGICAL CLASSIFICATION OF BACTERIA)
A) Cocci:These types of bacteria are unicellular, spherical or elliptical shape. Either
they may remain as a single cell or may aggregate together for various configurations.
They are as follows:
Monococcus:– they are also called micrococcus and represented by single, discrete
round Example: Micrococcus flavus.
Diplococcus:– the cell of the Diplococcus divides ones in a particular plane and after
division, the cells remain attached to each other. Example: Diplococcus pneumonia.
Streptococcus: – here the cells divide repeatedly in one plane to form chain of cells.
Example: – Streptococcus pyogenes.
Tetracoccus: – this consists of four round cells, which defied in two planes at a right
angles to one another. Example: – Gaffkya tetragena. Staphylococcus: – here the cells
divided into three planes forming a structured like bunches of grapes giving and
irregular configuration. Example: – Staphylococcus aureus.
Sarcina: -in this case the cells divide in three planes but they form a cube like
configuration consisting of eight or sixteen cells but they have a regular shape.

7. B) Bacilli: – These are rod shaped or cylindrical bacteria which either remain
singly or in pairs. Example: –Bacillus cereus.
C) Vibro: – The vibro are the curved, comma shaped bacteria and represented
by a single genus. Example: – Vibro cholerae.
D) Spirilla: – These type of bacteria are spiral or spring like with multiple
curvature and terminal flagella. Example: –Spirillum volutans.

8. Others
Actinomycetes are branching filamentous bacteria, so called because of a
fancied resemblance to the radiating rays of the sun when seen in tissue
lesions (from actis meaning ray and mykes meaning fungus).
Mycoplasmas are bacteria that are cell wall deficient and hence do not
possess a stable morphology. They occur as round or oval bodies and as
interlacing filaments.

15. Spore forming bacteria:
Those bacteria that produce spore during unfavorable condition.
These are further divided into two groups:
i) Endospore forming bacteria: Spore is produced within the bacterial cell.
Examples. Bacillus, Clostridium, Sporosarcina etc
ii) Exospore forming bacteria: Spore is produced outside the cell.
Example. Methylosinus
Non sporing bacteria:
Those bacteria which do not produce spores.
Eg. E. coli, Salmonella.

16. THANK YOU