ugc - csir topic

SEMINAR-II: 

SEMINAR-II SUBMITTED BY: M.ANANDHARAJ 1 st M.Sc -MICROBIOLOGY DEPARTMENT OF BIOLOGY GANDHIGRAM UNIVERSITY

SYNOPSIS: 

SYNOPSIS ORGANIZATION OF GENES AND CHROMOSOMES: operon , unique and repetitive DNA, interrupted genes, gene families, structure of chromatin and chromosomes, heterochromatin, euchromatin , transposons . CELL DIVISIONS AND CELL CYCLES: mitosis and meiosis, their regulation, steps in cell cycle, regulation and control of cell cycle.

SYNOPSIS: 

SYNOPSIS MICROBIAL PHYSIOLOGY: growth yield and characteristics, strategies of cell division, stress response.

OPERON: 

OPERON An operons a set of genes which are linked and are under the control of one promotor or operator. These genes accomplish one single task. An operon basically consists of two categories of genes they are, 1)Structural genes 2)Control genes Regulator genes Promotor gene Operator gene

PowerPoint Presentation: 

1)STRUCTURAL GENE: These genes are segments of DNA, which code for functional peptides, or enzymes or protein. 2)CONTROL GENES: These are genes which are primarily responsible for controlling the structural genes by producing an inducer or repressor substance.

PowerPoint Presentation: 

They are basically three types of genes i )REGULATOR GENES: The regulator gene(r) produces some specific enzymes which act as repressor substances. This repressor binds to the operator gene and thus stops the expression of structural genes.

PowerPoint Presentation: 

ii)PROMOTER GENE: The promoter gene (p) is the DNA segment at which RNA polymerase binds. It initiates the transcription of the structural genes. iii)OPERATOR GENE: The operator gene (o) is the segment of DNA which excercises a control over transcription. It lies close to the structural gene and the repressor binds to it.

Lac OPERON: 

Lac OPERON Proposed by JACOB and MONAD in 1961. They answering how the bacteria metabolizes the ‘lactose’. The regulator gene codes for a protein called ‘repressor’. When the lactose present in the media repressor fail to bind operator gene. There are three structural genes in the lac operon , called ‘ cistron -Z’ , ‘ cistron -Y’, ‘ cistron -A’.

PowerPoint Presentation: 

Cistron -Z codes for an enzyme called B- galactosidase , This enzyme cleaves the lactose into galactose and glucose. Cistron -Y codes for “ galactosidase permiase ” (protein), it facilitate transfer of lactose from outside into the cell. Cistron -A codes for “ galactoside transacetylase .

trp OPERON: 

trp OPERON The trp operon consists of the genes for the enzymes that are needed to make the amino acid “tryptophan”. Similar to lac operon the protein trp operon binds to the operator gene when the tryptophan concentration is high in the medium and do not synthesis tryptophan. It consists of 5 structural gene they are trpE , trpD , trpC , trpB , trpA .

REPETITIVE DNA: 

REPETITIVE DNA Nucleotide sequences in DNA that are present in the genome as numerous copies. These sequences are not code for polypeptides. One class of repetitive DNA, termed as “highly repetitive DNA”. It is found as short sequences,5-100 nucleotides repeated thousands of time in a single long stretch. It typically comprises 3-10% of the genomic dna and is predominantly satellite DNA.

REPETITIVE DNA: 

REPETITIVE DNA

INTERRUPTED GENE: 

INTERRUPTED GENE An interrupted gene (also called a split gene ) is simply a strand of DNA that contains both introns and exons . Most higher-level eukaryotes have interrupted genes and have longer introns than exons . And also found in some bacteria. This is affect the protein synthesis.

GENOME: 

GENOME Genome : Complete complement of an organism’s DNA. Includes genes (control traits) and non-coding DNA organized in chromosomes .

GENE: 

GENE A gene is a polynucleotide chain consists of segments each controlling a particular trait. Gene is three types they are Cistron : unit of function Recon: unit of recombination Muton : unit of mutation

GENE: 

GENE

CISTRON: 

CISTRON Term coined by “BENZER” Cistron is a portion of DNA specifying single polypeptide chain. A single mRNA is transcribed by a single gene it is said to be “ monocistronic ”. A single mRNA is also transcribed by more than one gene and it is said to be “ polycistronic ”.

CISTRON: 

CISTRON

RECON: 

RECON A recon is the smallest unit of DNA capable of recombination. Earlier, it was thought that crossing over occurs between two genes. In 1962, Benzer demonstrated that the crossing over or recombination occurs within a functional gene or cistron . In a cistron the recombinational units may be more than one. Thus, the smallest unit capable of undergoing recombination is known as recon

MUTON: 

MUTON BENZER coined the term muton . Which denotes the smallest unit of chromosomes that undergoes mutational change. Therefore cistron is largest unit followed by recon and muton .

GENETIC ELEMENTS: 

GENETIC ELEMENTS Genes are considered as genetic elements,which are encoded in DNA molecules which organised into a specified structure called “chromosomes”. Based on organization of chromosomes, living organisms are classified into “prokaryotes and eukaryotes”.

PROKARYOTIC CHROMOSOMES: 

PROKARYOTIC CHROMOSOMES Don’t have distinct membrane bound nucleus. Have a single circular and supercoiled DNA, which harbour of most all the genes. Compared to the size of the bacterial cell the size of the chromosome length is much long.

NUCLEOIDES: 

NUCLEOIDES Central portion of the prokaryotic cell always under electron microscopy darker area containing DNA and proteins known as “ nucleoides ”. Proteins are histones . The remaining portion of the cell protoplasm is called as the “cytoplasm”.

PLASMIDS: 

PLASMIDS In many bacteria apart from the main circular chromosomes, additional small DNA polynucleotide namely “plasmids” which contains few genes. Defined as the extrachromosomal,capable of self replicating genes. Example: antibiotic resistance gene.etc..

TYPES OF PLASMIDS: 

TYPES OF PLASMIDS 1) Resistance plasmid or R plasmid. 2) Fertility plasmid or F plasmid. 3) Col plasmid. 4) Degradative plasmids. 5) Virulance plasmids.

EUKARYOTIC CHROMOSOMES: 

EUKARYOTIC CHROMOSOMES Eukaryotic chromosomes are classified into four types based on morphoplgy . METACENTRIC: SUBMETACENTRIC: ACROCENTRIC: TELOCENTRIC:

CHROMATIN: 

CHROMATIN Chromatin is the combination of DNA and proteins. The primary functions of chromatin are to package DNA into a smaller volume to fit into the cell. To strengthen the DNA to allow mitosis and meiosis and prevent the DNA damage. And to control gene expression and DNA replication. Chromatin is only found in eukaryotic cell.

GENERAL FEATURES OF CHROMOSOMES: 

GENERAL FEATURES OF CHROMOSOMES 1) KARYOTYPE: It is a standardizes arrangement of all the chromosomes of a cell. KARYO- nucleus, TYPE- half. 2) IDEOGRAM: a chromosome preparation is photogarphed , then the homologus chromosomes paired and set out in order. 3) CHROMOSOMAL BANDING: a) G bands b) C bands C) R bands

a) G BANDS: 

a) G BANDS Obtained with giemsa staining. Stain specific for the phosphate group of DNA. The process causes chromosomes to stain as a dark G bands and pale interbands . USES: identifying chromosomes Gives overall organization of DNA and genes. G band rich in adenine and thymine. Interbands rich in guanine and cytosine.

b) C BANDS: 

b) C BANDS C bands are giemsa stained bands after treated with NaOH . The C stands ‘ centromere ’ Because bands represent constitutive heterochromatin surrounding the centromere .

c) R BANDS: 

c) R BANDS R bands are visible with a technique that stains the regions between G bands. Here the chromosomes are fixed, stained with giemsaand then viewed with a phase contrast microscope. Since the dark-light pattern is the opposite of the G-bands pattern, these bands are called ‘reverse bands’ or ‘R bands’.

EUCHROMATIN: 

EUCHROMATIN Euchromatin is a lightly packed form of chromatin (DNA, RNA, and protein). Unlike heterochromatin, it is found in both cells with nuclei (eukaryotes) and without nuclei (prokaryotes). Euchromatin participates in the active transcription od DNA and mRNA products.

HETEROCHROMATIN: 

HETEROCHROMATIN Heterochromatin is a tightly packed form of DNA. Two types of heterochromatin Constitutive heterochromatin: it is present in centromere , genetically it is inactive. Intercalary heterochromatin: it is present in chromosome arm and also inactive.

EU& HETERO CHROMATIN: 

EU& HETERO CHROMATIN

PowerPoint Presentation: 

s. no PROPERTIES EUCHROMATIN CONSTITUTIVE HETEROCHROMATIN INTERCALARY HETEROCHROMATIN 1 Relation to bands R bands C bands G bands 2 Location Chromosomes arm Centromeric Chromosome arm 3 Condition during interphase Dispersed Condensed Condensed 4 5 Genetic activity Relation to chromosome Active Intra chromomeric Inactive Centromeric chromosome Inactive Intercallary chromosome

SPECIALIZED CHROMOSOMAL STRUCTURE: 

SPECIALIZED CHROMOSOMAL STRUCTURE 1) CENTROMERES 2) TELOMERS AND 3) NUCLEAR ORGANIZER REGIONS (NOR).

CENTROMERES: 

CENTROMERES Centromeres are the site at wich the spimdle attaches during cell division. Any fragment which loses it’s connection to a centromere will not segregate to daughter cells at the end of the division. POINT CENTROMERE: which is attach to single microtubule during meiosis or mitosis. REGIONAL CENTROMERE: in higher eukaryotes have larger centromeric regions that attach more microtubules.

CENTROMERE: 

CENTROMERE

TELOMERES: 

TELOMERES The ends of linear chromosome is called “telomere”. They contain multiple repeats of simple, short DNA sequences. Eg : in human – TTA GGG It act as a molecular marker of aging process. It prevents the recombination between the ends of different chromosomes.

TELOMERE: 

TELOMERE

NOR’S: 

NOR’S Nor’s are usually found at “secondary constrictions”. They consists of tandemly repeated 5.8s, 18s and 28s rRNA genes. During interphase , the NOR decondenses can be incorporated into a single nucleolus.

HISTONES: 

HISTONES Histones are a group of small proteins with molecular masses of less then 23 Da. At physiological P H they have a positive charge due to the high frequency of amino acid ‘lysine and arginine ’. Histones are five types H 1, H 2 a, H 2 b, H 3 and H 4.

NUCLEOSOME: 

NUCLEOSOME The basic building blocks of chromatin structure, which consists of a core of histones around the DNA. The core is dimer,which consists of one H 2 a, one H 2 b, a tetramer consists of two H 3 and two H 4 histones .

PowerPoint Presentation: 

- Core DNA = 146 bp - Linker DNA = 8-114 bp (usually 55bp) - DNA turns 1 and ¾ times around histone octamer.

Mobile Genetic Elements: 

Mobile Genetic Elements Transposons or Transposable elements ( TEs ) move around the genome

Transposable elements in prokaryotes: 

Transposable elements in prokaryotes Insertion sequence (IS) elements Transposons ( Tn ) Bacteriophage Mu

Insertion sequence (IS) elements: 

Insertion sequence (IS) elements Simplest type of transposable element found in bacterial chromosomes and plasmids Encode only genes for mobilization and insertion Range in size from 768 bp to 5 kb IS1 first identified in E. coli ’s glactose operon is 768 bp long and is present with 4-19 copies in the E. coli chromosome Ends of all known IS elements show inverted terminal repeats ( ITRs )

TRANSPOSONES: 

TRANSPOSONES Similar to IS elements but are more complex structurally and carry additional genes 2 types of transposons : Composite transposons Noncomposite transposons

TRANSPOSONES: 

TRANSPOSONES

Composite Transposons : 

Composite Transposons Tetracycline resistance is carried by a transposable element The transposon is a composite transposon , composed of IS-elements flanking an included sequence, in this case containing an antibiotic resistance gene IS10R is an autonomous element while IS10L is non-autonomous Composite transposons probably evolved from IS elements by the chance location of a pair in close proximity to one another. Inactivation of one element by mutation would not harm ability to transpose and would assure continued transposition of the entire transposon

COMPOSITE TRANSPOSONES: 

COMPOSITE TRANSPOSONES

Noncomposite transposons (Tn): 

Noncomposite transposons ( Tn ) Carry genes (e.g., a gene for antibiotic resistance) Ends are non-IS element repeated sequences Tn3 is 5 kb with 38-bp ITRs and includes 3 genes; bla ( - lactamase ) , tnpA ( transposase ), and tnpB ( resolvase , which functions in recombination)

INTRODUCTION: 

INTRODUCTION “The process of cell division which results in the production of two daughter cells from a single parent cell”

INTERPHASE THE CELL PREPARES FOR DIVISION : 

INTERPHASE THE CELL PREPARES FOR DIVISION *ANIMAL&PLANT CELL Nucleus clearely defined Chromosomes not yet visible DNA replicated Organelles replicated Cell increases in size

PROPHASE THE CELL PREPARE FOR NUCLEAR DIVISION: 

PROPHASE THE CELL PREPARE FOR NUCLEAR DIVISION *ANIMAL&PLANT CELL DNA packaged into chromosomes Nuclear envelop is disappears Centrioles move to opposite sides of the cell.

METAPHASE THE CELL PREPARES CHROMOSOMES FOR DIVISION: 

METAPHASE THE CELL PREPARES CHROMOSOMES FOR DIVISION *ANIMAL&PLANT CELL Chromosomes line up at the center of the cell. Spindle fibres attach to centromeres on the chromosomes. Centrioles reach the opposite poles of the cell.

ANAPHASE THE CHROMOSOMES DIVIDE: 

ANAPHASE THE CHROMOSOMES DIVIDE *ANIMAL&PLANT CELL Spindle fibres contract and pull chromosomes apart. Half of each chromosomes ( chromatid ) moves to each hemisphere. Unattached spindle fibres push against each other on the sides of the cell and it begins to elongate.

TELOPHASE&CYTOKINESIS THE CYTOPLASM DIVIDES: 

TELOPHASE&CYTOKINESIS THE CYTOPLASM DIVIDES *ANIMAL CELL DNA spreads out. 2 nuclei form. Contractile ring causes a cleavage furrow to form the 2 new daughter cell. *PLANT CELL -DNA spreads out. -2 nuclei form. -cell plate forms new cell wall between the nuclei to form the 2 new daughter cells.

TELOPHASE: 

TELOPHASE

MEIOSIS 1: 

MEIOSIS 1 First division of meiosis Prophase 1: Each chromosome dupicates and remains closely associated. These are called sister chromatids . Crossing-over can occur during the latter part of this stage. Metaphase 1 : Homologous chromosomes align at the equatorial plate. Anaphase 1 : Homologous pairs separate with sister chromatids remaining together. Telophase 1 : Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair.

MEIOSIS 2: 

MEIOSIS 2 Second division of meiosis: Gamete formation Prophase 2 : DNA does not replicate. Metaphase 2 : Chromosomes align at the equatorial plate. Anaphase 2 : Centromeres divide and sister chromatids migrate separately to each pole. Telophase 2 : Cell division is complete. Four haploid daughter cells are obtained.

MICROBIAL GROWTH: 

MICROBIAL GROWTH Growth can be defined as the final expression of the physiology of an organism. In the case of microorganism, it is very essential event for their survival. Growth of a microorganism implies an increase in the amount of protoplasm,the formation of new structures and new cells.

PowerPoint Presentation: 

The term ‘balanced growth’ means that the cell components increase in proportion to each other. The ‘unbalanced growth’ means that components of a new cell increase in a nonconstant relationship to each other. ‘Yield’ is a measure of the amount of growth obtained. ‘ Rate’ is a measure of it’s speed.

COMPLEX PROCESS OF GROWTH: 

COMPLEX PROCESS OF GROWTH 1)Entrance of basic mutritions into the cell. 2)Conversion of their components into energy and vital cell constitutions. 3)Replication of their genetic material. 4)Increase in size and mass of the cell. 5)Division of the cell into two daughter cells,each containing a copy of the genome and other vital compounds.

PHASES OF GROWTH: 

PHASES OF GROWTH 1) LAG PHASE 2) LOG PHASE 3) STATIONARY PHASE AND 4) DEATH PHASE.

1) LAG PHASE: 

1) LAG PHASE This phase is otherwise called as adaptation phase in which division and metabolism take place slowely . The period of time between the introduction of a microorganism into a culture medium and the time it begins to increaseexponentially called also lag period.

2) LOG PHASE: 

2) LOG PHASE In this phase, the organism is supplied with abundant nutrient and it can grow as rapidly as possible. The metabolic systems of the organism are operating efficiently at their maximum rate. This phase is otherwise called exponential or idio phase. In this phase cell synthesize primary metabolites like amino acids, alcohols, sugars, etc. The growth rate remains constant until yhe medium is exhausted.

3)STATIONARY PHASE: 

3)STATIONARY PHASE All cultures of microorganisms eventually reach a maximum population density. In this phase one or more critical nutrients are diminished or exhausted and toxic products, acids and alcohols are accumulated. Growth of the organism does not take place. Some organism show slow growth and some die.

4)DEATH PHASE: 

4)DEATH PHASE Death phase is a physiological point at which cell deaths exceed cell births. More specifically, viable count declines. "During the decline phase , many cells undergo involution ---that is, they assume a variety of unusual shapes, which makes them difficult to identify."

STRESS RESPONSE: 

STRESS RESPONSE Introduction: when supplied with sufficient nutrients and optimal growth temperature,pH , oxygen levels and and solute concentration microbes will grow a maximum growth rate. variations of these parameters can affect the maximum growth rate, and it represent an ‘environmental stress’ for the microbes.

OSMOTIC STRESS : 

OSMOTIC STRESS The concentration of solutes ( eg : salts, ions, metabolites) plays a critical role in microbial growth. Hypertonic or hyperosmotic condition results in water loss from the cytoplasm causing the cell to “ shrink “. Hypotonic or hyperosmotic conditions results in an influx of water into cytoplasm, which cause cell to swell ( plasmolysis ) and burst ( osmoticlysis ). The isotonic condition which means equilibrium is maintained inside and outside of the cell.

AEROBIC TO ANAEROBIC TRANSITIONS: 

AEROBIC TO ANAEROBIC TRANSITIONS Many of the microbes can not live to changing from aerobic to anaerobis condition but some facultative microbes ( eg : E.coli ) capable of modifying their metabolism to accommodate growth under aerobic or anaerobic conditions by alternates in the rate, route and efficiency of pathways of electron flow.

PH STRESS & ACID TOLERANCE: 

PH STRESS & ACID TOLERANCE Microbes can grow over a wide range of hydrogen ion concentrations (pH). For example: Acidophilic bacteria grow sulfer springs pH at -1. Alkalophilic bacteria grow high pH condition -11. Neutrophilic bacteria can grow pH at 5-9.

PowerPoint Presentation: 

The neutrophiles don’t grow in high acidic conditions or base so they respond to an acidifying pH is by producing enzymes that can convert acidic metabolites to neutral ones. Ex: glutamate decarboxylase , lysine decorboxylase of E.coli . The genetic and physiological changes that occur in the cell are referred as the “acid tolerance response” (ATR). Full induction of ATR results in the increased expressions of atleast 50 newly synthesized or existing proteins called “acid shock proteins”.

THERMAL STRESS: 

THERMAL STRESS As with pH, microbes exhibit a wide range of temperatures at which they can grow. Ex: Thermophiles - grow in 90 0 c Psycrophiles – grow in 0 0 c Mesophiles – grow in 20-40 0 c Upon a shift from 30 – 42 0 c the bacteria transientlyincrease the rate of synthesis of a set of proteins called “Heat shock proteins” (HSPs).

PowerPoint Presentation: 

This HSPs are required for cell growth or survival at more elevated temperatures (Thermo tolerance). Ex : more than 50 HSPs in E.coli . SONE, DNAJ, RNA POLYMERASE, GroES , Gro EL, LON PROTEASE.

NUTRIENT STRESS & STARVATION: 

NUTRIENT STRESS & STARVATION The lack of nutrient in the medium is called nutrient stress or starvation. Many microbes are competing for available small amount of nutrient. In this condition microbes respond by inducing the expression of upto 50 or more new proteins or pre existing proteins. The genetic and physiological reprogramming is called “starvation- sterss response.

STRESS RESPONCE: 

STRESS RESPONCE

SUMMARY: 

SUMMARY OPERON-An operons a set of genes which are linked and are under the control of one promotor or operator. REPETITIVE GENE- Nucleotide sequences in DNA that are present in the genome as numerous copies. INTERRUPTED GENE-An interrupted gene (also called a split gene ) is simply a strand of DNA that contains both introns and exons . GENOME- Complete complement of an organism’s DNA. Includes genes (control traits) and non-coding DNA organized in chromosomes .

PowerPoint Presentation: 

GENE-A gene is a polynucleotide chain consists of segments each controlling a particular trait. CHROMATIN-Chromatin is the combination of DNA and proteins . The primary functions of chromatin are to package DNA into a smaller volume to fit into the cell. TRANSPOSONES-Similar to IS elements but are more complex structurally and carry additional genes. MITOSIS- The process of cell division which results in the production of two daughter cells from a single parent cell.

PowerPoint Presentation: 

MICROBIAL GROWTH-Growth can be defined as the final expression of the physiology of an organism.In the case of microorganism, it is very essential event for their survival. STRESS RESPONSE- when supplied with sufficient nutrients and optimal growth temperature,pH , oxygen levels and and solute concentration microbes will grow a maximum growth rate.

REFERENCES: 

REFERENCES MOLECULAR BIOTECHNOLOGY BY MUKESH PASUPULETI. MICROBIOLOGY BY LANSING M.PRESCOT. GERALD KARP, CELL AND MOLECULAR BIOLOGY. WWW.ncbi.nlm.nih.ogv www.biology-online.org www.biozone.co.uk www.dbt.org www.wikipedia.com