google-site-verification: google59 KNOW ABOUT BACTERIA - TYPES, NUTRITION, RESPIRATION, REPRODUCTION - Biology is life

KNOW ABOUT BACTERIA - TYPES, NUTRITION, RESPIRATION, REPRODUCTION

 Bacteria

These unicellular, prokaryotic organisms contain cell wall (feature of

plant cells only). These are approximately 4000 species of bacteria,

with cosmopolitan occurrence. Bacteria can be regarded both friends

and foes on the basis of interaction with human beings.

An average weight human (~ 70 kg) has about 2.5 kg of bacteria in the

form of gut microflora to supplement the proper digestion and other

metabolic functions



(i) Archaebacteria

These are the group of most primitive prokaryotes. They have a cell

wall, made up of protein and non-cellulosic polysaccharides. The

presence of 16 srRNA, makes them unique and helps in placing in a

separate domain called archaea between bacteria and eukarya.

Archaebacteria can live under extreme hostile conditions like salt

pans, salt marshes and hot sulphur springs. They are also known as

living fossils, because they represent the earliest form of life on earth.

Archaebacteria can be used for

(a) Experimentation for absorption of solar radiation.

(b) Production of gobar gas from dung and sewage.

(c) Fermentation of cellulose in ruminants.



(ii) Eubacteria

Eubacteria are ‘true bacteria’ which lack nucleus and membrane bound

organalles like mitochondria, chloroplasts, etc. Eubacteria are usually

divided into five phylums– Spirochetes, Chlamydias, Gram- positive

bacteria, Cyanobacteria and Proteobacteria.


Nutrition in Bacteria

The process of acquiring energy and nutrients., is called nutrition.

On the basis of mode of nutrition, bacteria are of two types–

autotrophic and heterotrophic. About 1% bacteria show autotrophic

mode of nutrition and the rest are of heterotrophic habit.

Chemosynthetic bacteria oxidise various inorganic substances such as

nitrates, nitrites and ammonia and use the released energy for their

ATP production.



Respiration in Bacteria Other Monerans


These are as follows

1. Mycoplasma

● It was discovered by Nocard and Roux i

 1898. These are cell wall

less, aerobic and non-motile organisms. Due to the absence of cell wall

and pleomorphic nature, they are commonly called as jokers of living

world.

● The mycoplasmas are also known as Pleuro Pneumonia Like

Organisms (PPLO). These are the smallest living cells, yet

discovered, can survive without oxygen and are typically about 0.1 µm in diameter


2. Actinomycete

● The members of a heterogeneous group of Gram-positive, are

generally anaerobic bacteria noted for a filamentous and branching

growth pattern. It results in most forms in an extensive colony or

mycelium

● Morphologically, they resemble fungi because of their elongated cells

that branch into filaments or hyphae. During the process of

composting, mainly thermophilic and thermotolerent Actinomyces

are responsible for the decomposition of the organic matter at

elevated temperature.

● Generally, Actinomycetes grow on fresh substrates more slowly than

other bacteria and fungi. During the composting process, the

Actinomycetes degrade natural substances such as chitin or

cellulose.

● Natural habitats of thermophilic Actinomycetes are silos, corn mills


3. Cyanobacteria/Blue-Green Algae (BGA)

● They are Gram-negative photosynthetic prokaryotes which perform

oxygenic photosynthesis. These can live in both freshwater and

marine habitats and are responsible for ‘blooms’ in polluted water

(eutrophication).

● They have photosynthetic pigments, chlorophyll-a, carotenoids

and phycobilins and food is stored in the form of cyanophycean

starch, lipid globule and protein granules.

● Cyanobacteria have cell wall formed of peptidoglycan, naked DNA,

70S ribosomes and the absence of membrane bound organelles like

endoplasmic reticulum, mitochondria, Golgi bodies, etc.

● The red sea is named after the colouration provided by red coloured

cyanobacteria i.e., Trichodesmium erythraeum.

● Cyanobacteria can fix atmospheric nitrogen through a specific

structure called heterocyst. These are modified cells in which

photosystem-II is absent hence, non-cyclic photophosphorylation

does not take place. Nitrogen-fixation is performed through enzyme

nitrogenase, present in it.



4. Rickettsia


 ● These are small, aerobic and Gram-negative bacteria. They belong to

 phylum–Proteobacteria, which are capable of growing in low level of

 nutrients and have long generation time relative to other

 Gram-negative bacteria.

 ● Rocky Mountain Spotted Fever (RMSF) is a tick borne human

 disease caused by Rickettsia rickettsii, an obligate, intracellular

 bacteria. , . s . n Respiration occurs in the plasma membrane of bacteria. Glucose is

broken down into carbon dioxide and water using oxygen in aerobic

cellular respiration and other molecules such as nitrate (NO ) 3

in

anaerobic cellular respiration.

Reproduction in Bacteria

Bacteria reproduce asexually and sexually both.

Asexual Methods

Asexually, bacteria reproduce by following methods

● Fission Bacteria divide both laterally and longitudinally.

● Budding Vegetative outgrowths result into new organisms after

maturity.

● Spore formation Non-motile spores like conidia, oidia and

endospores are formed.

Sexual Methods

Although sexes are not differentiated in bacteria, following methods of

genetic recombination are categorised under sexual reproduction in

bacteria.

● Transformation F Griffith (1928), Genetic material of one

bacteria is transferred to other through conjugation tube.

● Conjugation Lederberg and Tatum (1946), Transfer of genetic

material occurs through sex pili.

● Transduction Zinder and Lederberg (1952), Transfer of genetic

material occurs by bacteriophage.

Economic Importance of Bacteria

Economically, some bacteria are useful in producing various useful

substances like curd, cheese, antibiotics and vinegar, etc. While other

bacteria cause several chronic diseases in humans, plants and other animals etc .

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