Introduction of Protoplasts

         The bacteria without cell wall but having cell membrane ,capsule and protoplasm is called protoplast.

                             Some bacteria when treated with enzyme lysosome, their cellwall dissolve without destroying any internal structure . This is because the enzyme lysozyme hydrolyses the bond between N-acetyl muramic acid and N-acetyl glucosamine. These bacteria without cell wall is called Protoplast. Protoplast posses many of the physiological characteristics except they are non-motile ,unable to divide.

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.

b) Resistance factor or R-factor.(RF)

The R- factor are extra extra chromosomal  genes which carry information of resistance against variety of antibiotics. It gets transferred to the receipient along with sex factor. These genes get transferred rapidly to the antibiotic sensitive cells by conjugation. These genes get transferred between bacteria like E.coli ,Salmonella typhi and Shigella dysentriae. It has been observed to increase resistance against four iwdesly used antibiotics like sulphanilamide, streptomycin, chloramphenicol and tetracycline.

Conjugation by Sexduction

It is the process of transferring genetic material from donor to recipient by a sex factor. In this method , from the endogenote of HFr the F factor or sex factor disintegrate resulting the reversion of HFr to F⁺ state but this F⁺ factor along with small part of endogenote is called F factor and the cell is called F’ cell. When conjugation between F’ cell and F^- cell takes place ,the cell with some transferred genes takes place. In this way transfer of genes takes place.

Conjugation by episome

    The episome are the bacterial cell whose fertility factor integrate with endogenote and then replicate followed by migration of the combined endogenote ,. This cell with combined endogenote is called HFr( high frequency recombination) . When HFr and F^-comes together and recombination can take place,then HFr is called fertile male .During conjugation HFr duplicate and then one of loop break at  the junction of endogenote and fertility factor. The broken part with endogenote part move through conjugation tube .In this way transfer of genetic character takes place.

Conjugation by F particle

             The F⁺ and F^- bacteria first come in closer. The F⁺ cell produce filamentous structure called sex-pilus from cell wall which attach the cell wall of F^-to form conjugation tube .The F^- particle of F⁺ then duplicate and then replicate to form two strands . One remain in F⁺ cell and another passes through the conjugation tube and remain in F- as an independent F^- particle . Now the F^-changes to F⁺

a) Fertility factor and its forms

Sexual Reproduction in bacteria by Conjugation and sex factors

            Conjugation is a sexual type of reproduction in bacteria in which there is transfer of genes between two bacteria by directly coming in contact with each other. The conjugation was first described by Lederberg and Tatum(1946) in E.coli and other species of Gram –negative bacteria . Till now it hasn’t been found to be discovered in Gram –positive bacteria.

                   In the conjugation process the bacteria which donate genes or DNA is called donor cell or male cell and the other which receive the genes or DNA is called receipient cell or female cell. Each male cell posses an additional double stranded circular piece of small DNAin cytoplasm which is called a plasmid or sex factor . The sex factor is 1/1000 ^th size of enogenote( normal bacterial chromosome). Till now according to Lederberg and Tatum three types of sex factors are known. They are named as

a)     Fertility factor or F factor (FF)

b)    Resistance factor or R-factor.(RF)

c)     Colicin factor or Col-factor(CF)

Sexual Reproduction in Bacteria by Transformation

This method was first discovered by Griffttth in1928 in Streptococcus pneumonia which is responsible for causing Pneumonia in children. The pneumonia bacteria are of different types . They are named as type I,II,III,IV and so on . These pneumococcus are of two types, one with capsule and another without capsule.The one with capsule is called Smooth type or S-type and the other without capsule is called Rough type or R-type . The smooth type are more infectious or virulent then the R-type .This R-type is converted to S- type when they get suitable condition during transformation.                                      

             The pneumonia bacteria was examined with rats. Three groups of rats were taken and they were injected by different samples of bacteria. The first group was injected by non encapsulated R-type bacteria. The second group of rat was injected  

by heat killed encapsulated bacteria or R type .The third group was injected by the mixture of living R-type bacteria and heat killed non -encapsulated bacteria (S-type). The first group and second group of rats were not infected and continue to survive. The third group survive for some period but finally died and when their body was examined S- type encapsulated bacteria was isolated. This was explained by saying that heat killed encapsulated bacteria produced some substances which procided a medium for R-type non-encapsulated bacteria to produce capsulated bacteria called S-type.

Sexual Reproduction in Bacteria

Sexual reproduction in bacteria is different from Eukaryotic organism. In Eukaryotic organisms ,the male and female gamete cells are produced whose fusion takes place to form zygote but sexual reproduction in bacteria is different because no gamete cells are produced and thus no fusion of cells to form zygote takes place .In bacteria genetic recombination takes place between two bacterial cells.The bacteria which transfer a part of genetic material is called donor and which receive the genetic material is called receipient. Thus the bacterial cell become diploid cell from haploid cell and since a part of genetic material are only exchanged .So it is called merozygote or partial zygote. The merozygote contain all DNA of its past cell and exogenote or a part of DNA from others. This genetic recombination between two bacteria takes place in three methods namely transformation, conjugation and transduction.

Reproduction in bacteria

Bacteria can reproduce both by asexual and sexual method. So it is said reproduction in bacteria as

1)     Asexual reproduction

2)     Sexual reproduction

1)     Asexual reproduction

          Bacteria can reproduce asexually by simple fission and binary fission method. Both fissions takes place during favourable climate.

The whole process can be grouped into three steps. The whole process can be grouped into three steps. They are

a)     Depletion of genetic material (DNA)

b)    Separation of DNA into newly formed two independent cells.

c)     Cytokinesis .

Since bacteria donot have spindle fibre so the two daughter cells formed may or may not contain equall loofs of DNA. So some time vinary fission result in the formation of cell with out nucleoid. And another cell containing two nucleoid. The genetically identical population of bacteria produced from asexual reproduction from a single parent is called clone.

 

Introduction of photo-hetrotrophs and chemo-hetrotrophs

 3) Photo-heterotrophs:

           This bacteria uses organic compound as the source of carbon. They oxidizes  the organic compound to get energy for growing. This bacteria is also known as Photo-organotrophs. Example Non –sulphur bacteria.

 4)  Chemo-hetrotrophs:

                     This bacteria is also called  chemo-organotrophs. This also             use organic compoundas the source of carbon . They produce energy from oxidation –reduction of organic compound which is used for growth of bacteria. Example E. coli

detail of types of chemo-autotrophs

Nitrifying bacteria

                      These bacteria makes nitrogen available to plants. They are present in soil. The Nitrosomonas and Nitrosococcus oxidizes ammonia to nitrate. The Nitrobactera and Bactoderma converts nitrite to nitrate.

Reaction      nitrosomonas

 2NH₃ +3O₂    →    2HNO₂ + 2H₂O +  158 Kcalorie

                                    nitrobacter

  HNO₂ + O₂ →    HNO₃ + 43kcalorie

Hydrogen bacteria

                 These bacteria oxidizes hydrogen to water in presence of oxygen .Example Hydrogenomonas

Reaction

 2H₂ +O₂ →  2H₂O + 56 kcalorie

Sulphur bacteria

             This bacteria is found in hot spring  containing hydrogen sulphide .They first oxidizes hydrogen to sulphur. This sulphur is conerted to sulphuric acid. The acid undergo reaction with soil to form sulphate. Example Beggiatoa and Thiobacillus thioxidans.

  Reaction

2H₂S +O₂  → 2S + H₂O +energy

2S +  2 H₂   → 2H₂SO₄  + energy

Iron bacteria

      This bacteria changes ferrous compound into ferric compound. The energy evolved from the oxidation is used for converting carbondioxide to food. Example or iron bacteria are Leptothrix, Cladothrix, Spiruphyllum and Ferrobacillus.

Reaction

 2FeHCO₃ + H2O +O  →  2Fe(OH)₃ + CO₂ +29 K calorie

 2FeCO₃ + 6H₂O   →  Fe(OH)₃ + 4CO₂ + 81 k calorie

Methane bacteria

    This bacteria oxidizes methane to CO2 . Thus methane provide both cargon and energy.

 CH₄ +O₂  →  CO₂ + H₂O + energy

Example : Methanosomonas

Introduction of Chemoautotrophs with its type

    Chemoautotrophs are the bacteria which uses energy evolved from chemical reaction as source of energy . It also uses atmospheric CO2 to prepare food. Chemoautotrophs are of following types

                  I.      Nitrifying bacteria

               II.      Hydrogen bacteria

            III.      Sulphur bacteria

           IV.      Iron bacteria

              V.      Methane bacteria