What are bacteria?
The organism which are invisible in naked eye and only visible with the help of compound microscope are called microorganism. Majority of these microorganism or microbes in the earth are the bacteria. The bacteria are prokaryotic in nature because their genetic material is not contained within the nuclear membrane. They are devoid of stock the major sale organelles what not have a true unit membrane. Bacteria are Cosmopolitan inhabit works as a parasite, saprophyte or as a symbiont. In biological science the branch in microbiology the part deals with bacteria is called bacteriology.
So, bacteria are a group of unicellular, microscopic, prokaryotic organisms, which can survive parasitically, saprophytically and also as a simbiont.
Systematic position of bacteria: –
Different parts of Bacteria
it was considered by Leeuwenhoek that bacteria as animalcules and placed them under animal kingdom primarily as bacteria exhibit locomotion like animals. But later scientist F.J. Cohn considered bacteria in the group of plants. Cause of such consideration is as follows: –
i) Bacteria have cell wall.
ii) Some bacteria have been chlorophyll like the pigments and exhibit auto-tropic mode of nutrition.
iii) Some of the bacteria also show diffusion of soluble food.
Bacteria were also placed under Protista because of their similarity with unicellular animals like protozoa in having flagella or being parasite the in nature.
Characteristics of bacteria: –
The following characteristics have yet been noted:
i) Bacteria are unicellular organisms with a diameter less than 34 µ.
ii) They possess a well defined non-cellulosic cell wall, commonly called as peptidoglycan.
iii) Chlorophyll b is absent but it has replaced by chlorophyll a and chlorobium chlorophyll.
iv) Did nucleus is devoid of nuclear membrane.
v) The respiration of bacteria is carried out in the mesosomes.
vi) The DNA is simple, circular, non-complexed with histone protein.
vii) The unit membrane bound organelles like mitochondria, plastids Golgi body are absent.
viii) The photosynthetic recommends are stored within the chromatophores.
ix) The mitosis is replaced by the process of amitosis.
x) The site of protein synthesis is the 70S ribosome.
xi) The reproduction mostly occurs by vegetative and asexual manner.
xii) Rear sexual reproduction occurs by conjugation, transformation and transduction.
xiii) The end product of conjugation is a partial zygote or a merozygote.
xiv) They can survive as autotropic, heterotropic or symbiotic organisms most top which are parasitic in nature.
xv) The bacteria can produce various secondary metabolites useful to human beings in the form of enzymes of medicines.
xvi) It may play some beneficial role in human body like B-vitamin synthesis.
Consideration of bacteria as a plant:
Scientist F. J. Cohn considered the bacteria as a member of plant kingdom due to the following causes:
i) It possess a distinct cell wall composed of polysaccharide, lipid and protein.
ii) Some bacteria can synthesize their own food because of having bacterio-chlorophyll.
iii) Most of the bacteria reproduce vegetatively.
iv) They can prepare vitamins in their bodies.
What is the size of bacteria?
The size of bacteria is greatly variable. The length of bacteria varies between 0.1 µ to 10 µ., while the diameter is between 0.5 µ to 1µ. Mycoplasma is the smallest bacteria of diameter 0.1 µ. Bacillus butschilliis a large bacteria, which is the length of 80 µ and width about 6 µ. The largest bacteria are Epulopicium fishelsoni with a diameter of about 600 µ. So there have different sizes of bacteria in our world.
Next we are going to discuss about the classification of bacteria. Click on ……..