MORPHOLOGY OF BACTERIA (MICROBIOLOGY NOTES)(SECOND YEAR B.PHARMACY NOTES) PCI SYLLABUS

MORPHOLOGY OF BACTERIA

BACTERIA:-

Bacteria diagram

STRUCTURE OF BACTERIA

Bacteria are unicellular, prokaryotic, free living microorganism capable of performing all the essential functions of life. The cell structure is simpler than that of other organisms as they are lack of nucleus and membrane bound organelles. Two protective coverings an outer cell wall and an inner cell membrane protects the bacterial cells from outside environment. Some bacteria, like the mycoplasmas, do not have a cell wall while some other bacteria may even have a third, outermost protective layer called the capsule.

They are microscopic microorganism that does not contain chlorophyll. DNA that either floats freely in a twisted, thread-like mass called the nucleoid, or in separate, circular pieces called plasmids. Bacteria are occurs at all natural environments like air, water, soil, food. They can survive extremes of temp, PH, oxygen, tension and atmospheric pressure.

MORPHOLOGICAL CLASSIFICATION BACTERIA:-

Morphology: - Morphology is the branch of biology that deals with the study of the size, shape, and structure of microorganism

As per the morphological basis, bacteria are classified in to six major groups which are as follows

1. SIZE OF BACTERIA

Bacteria are very small microorganism which is visible under the light microscope. Bacteria are measured in units of length called micrometers or microns. In general, the average size of most of the bacteria are between 0.2 and 2.0 um -.

Depending on size, bacteria are classified into several categories.

Ø Cocci = 0.5 to 1.0 µm

Ø Bacilli = 0.5 to 1.0 µm in breadth, 1.0 to 8.0 µm in length.

Ø Spiral bacteria = 1.0 µm to over 100 µm in length.

Ø Star shaped, filamentous, and lobed commonly fall in to a size range of 1.0 µm.

size of micro-organism

1. SHAPE OF BACTERIA:- Depending on their shape, bacteria are classified into several varieties

Ø Cocci:- (from kokkos meaning berry) spherical/oval shaped e.g. Micrococcus.

Ø Bacilli:-. (from baculus meaning rod) Rod shaped e.g. Bacillus anthracis.

Ø Vibrios:- Comma shaped, curve rods e.g. Vibrio comma.

Ø Spirilla: - Longer rigid rods/coiled forms e.g. Spirillum ruprem.

Ø Spirochetes: - (from speira meaning coil and chaite meaning hair) Slender/flexuous spiral forms.

Ø Actinomycetes:- branching filamentous bacteria e.g. Streptomyces species.

Ø Mycoplasmas:- They are cell wall deficient bacteria and hence do not possess a stable morphology. They occur as round or oval bodies with interlacing filaments.

ARRANGEMENTS OF BACTERIAL CELLS

The most common method of reproduction among bacteria is asexual binary fission. In this process each cells splits by forming two new cells. Cocci appear in several characteristics arrangements or groupings.

DIPLOCOCCI:- Cocci that split along one plane only. Tend to arrange themselves in pairs. E.g. Diplococcus pneumoniea.
STREPTOCOCCI:- This cells divide in one plane and remain attached, to form chains. E.g. streptococcus lactis.
TETRACOCCI:- This cells divide in two planes & live in groups of four. E.g.
STAPHYLOCOCCI:- This cells divide in three planes in an irregular pattern. Produce bunches of cocci as in grapes.
SARCINAE- This cell divides in three planes in a regular pattern. Produces a cuboidal arrangement of group of a eight cells.

Bacteria arrangement

Bacilli split only across their short axis. Arrangements of groupings formed by bacilli species are limited.

DIPLOBACILLI:- Appears as pairs. E.g. Klebisella pneumoniae.
STREPTOBACILLI:- Found in chains.E.g. Bacillus subtilis.
TRICHOMES:- Similar to chains but have a much large area of contact between the adjacent cells. The bacilli remain attached to each other at various angles by incomplete separation of the daughter cells, resembling the letter ‘V’ or ‘L’. E.g. Corynebacterium.