Bacteria: Properties

Bacteria: Properties

Bacteria (eubacteria) are microscopic and least differentiated living organisms, believed to be the first primitive organisms on our planet. They are the typical prokaryotes and also possess characters resembling both the plants and the animals. Bacteria show considerable variation in characters almost themselves, they possess many characters common to all. Such common characters of bacteria are the following.

1. They are omnipresent and occur in all possible habitats. 

2. Most of the bacteria have heterotrophic (absorptive) mode of nutrition, i.e., they absorb their food directly from their external environment, and may be saprophytic, mutualistic or parasitic. Some bacteria are autotrophic; they possess bacteriochlorophyll and synthesize their own food .

3.Bacteria are usually single - called and morphologically least complex of all the living organisms. 

4. They are either photosynthetic Or heterottrophic. In case of photosynthetic bacteria, Bacteriochlorophyll pigments,  are present, which are located within involuted cytoplasmic membranes. 

5. Bacterial cell wall is a dense layer surrounding the plasma membrane and functions to give shape and rigidity to the cell . The main constituent or back - bone of bacterial cell wall is peptidoglycan ( also known murein, muramic acid or mucopeptide),which is biochemically unique and is absent in cell walls of archea (archaebacteria) or any eukaryote.

6.A well organised nucleus, characteristic of eukaryotes, is lacking and descrete chromosomes are also absent. The nuclear material is not surrounded by nuclear membrane and is usually called nucleoid. 

7. Bacterial DNA have no histone proteins and nucleosomes. They also lack 'introns' , the non - coding sequences .

8. The organelles like mitochondria, endoplasmic reticulum, Golgi apparatus are absent. 

9. The function of mitochondria is carried out by complex localized infoldings of plasma membrane known as mesosomes .

10. Ribosomes occur abundantly and freely in the cytoplasm of a bacterial cell . Each ribosome has a sedimentation coefficient of 70S and is made up of two subunits of 50S and 30S each consisting of roughly equal amounts of rRNA and protein. 

11.Bacteria reproduce asexually and multiply most commonly by binary fission.

12. True sexual reproduction is absent . The sexuality is completed by genetic recombination methods called conjugation, transformation and transduction.

13. The motile bacteria possess one or more flagella. Each flagellum is composed of eight parallel chains of flagellin molecules , a type of protein.