Importance of bacteria in nitrogen fixing

Plants need nitrogen to grow well.Though nitrogen is found in air but it cannot be used by plants directly.This nitrogen is converted into nitrogen compound of elements present in earth by nitrogen fixing bacteria into nitrogen compound of elements present in earth by nitrogen fixing bacteria.

                     There are two types of nitrogen fixing bacteria. They are free living like Azotobacter and Clostridium and symbiotic bacteria like Rhizobium. This nitrogenous compound is taken by plants. When plants and animals die and their body contents are converted into ammino acid byby bacteria. The amminoacid is converted into ammonia by ammonifying bacteria. Some of ammonia pass into air and the rest are converted into ammonium salt.This ammonia salt is converted into nitrate by nitrifying bacteria.There are two types of nitrifying bacteria.They are Nitrosomonas and Nitrobacter.The nitrosomonas bacteria first oxidise ammonia salt into ammino nitrite. The nitrite is again oxidised to nitrate by nitrobacter. This nitrate compound is absorbed by plants.

Bacteria importance in soil fertility

Bacteria are useful for maintaining the fertility of  soil . It helps in fixing nitrogen in soil that can be used by plants. Some bacteria also helps in Sulphur cycle. Both the nitrogen fixing and sulphur cycle are important because they help plants in growing and maintaining the balance in nature.

Economic importancs of bacteria

Though bacteria are responsible for causing several dreadful diseases but still some are important for the various purposes. Some of the importance of bacteria can be listed in the following ways.

         1) Bacteria and soil fertility

         2) Bacteria as decomposers.

         3) Bacteria in sewage disposal

         4) Bacteria in diary products.

         5) Bacteria in various industries.

2)Specialized transduction

In this type of transduction the virus get adsorbed on the cell wall of bacteria and then it penetrate into the bacterial cytoplasm. It does not cause the breakdown of bacterial DNA. Instead it produce the repressor protein which prevent the transcription of the virus DNA into messenger RNA. At this state, the virus (phage) is called temperate phage. At this state, the virus DNA become integrated into bacteria chromosome (endogenote) . consequently the virus DNA become a segment of bacterial chromosome and then it replicate at the same rate of the bacterial DNA. The virus DNA in this state is known as Prophage.

       A bacterium that carries the virus at prophage stage is known 
      as lysogenic   bacterium as it gets destroyed later when the
     prophage become active  and re-enters into the lytic cycle.   
     These bacteria which suffer infection from temperate phage has
      immune to lysis (breakdown) after reinfection of similar 
     bacteriophage. Sometime this prophage is freed from bacterial 
     chromosome (endogenote) and accidentally it carries adjacent 
     gene from the bacterial chromosome. The prophage containing 
     some gene of bacteria when  infect other bacteria of an 
     appropriate strain ,these genes get transferred to the bacteria 
    chromosome and thus there is recombination of genes of previous
    bacteria and bacteria of appropriate strain.

1) Generalized transduction

                    In this type of transduction the virus adsorb to the host (bacteria) cell wall and inject its nucleic acid or DNA into the bacterial cell or cytoplasm. These DNA  produce enzyme in host cell which cause the host cell’s DNA to break into many fragments and directs the host metabolism to produce more virus DNA and its protein coats. After sometime the DNA of virus and the protein assemble to form a new viruses .During this assembling some of the small pieces of chromosome of bacteria get arranged in the chromosome of virus . During subsequent breakdown of bacterial cell the new viruses are released. The released virus when infect a new bacteria, it transfer not only its gene but also the genes of bacteria . This type of transduction is known as Generalized transduction.

 

Introduction of Transduction with its type

     This method of conjugation was first observed by Zinder and Lederberg in 1952 in Salmonella bacteria . In this method the gene  along with DNA transfer from one to another by a bacterial virus called bacteriophage.

            All the bacteriophage may not cause the breakdown of the host cell. The bacteriophage that cause the breakdown of host bacteria cell is called “virulent bacteriophage” The  bacteriophage which do not cause the breakdown of the host cell is called “temperate bacteriophage”. Depending on this ,there are two types of transduction . They are called

1)     Generalized transduction

2)     Specialized transduction

c) The colicin factor or col-factor

             It is a sex factor which is present in protoplasm of bacteria that get transferred during the conjugation . This colicin factor is respsnsible for production of certain protein or polypeptide antibiotic called colicin or bacteriocin .This factor was first observed in E.coli. This factor kills the bacteria which posses closely related strains or species.