microbiology at a glance: 2009

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ULTRA STRUCTURE OF BACTERIAL CELL

Microorganisms exist as either prokaryotes or eukaryotes. The prokaryotic cells are morphologically much simpler than eukaryotic cells. The prokaryotic cells lack internal membrane bound organelles that are present in the cytoplasm of eukaryotic cells...

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VIRUS

Virus literally means ‘poison’. They are also called as filterable molecules during olden days as they are able to pass through filter pores which do not permit bacteria to pass. They are the submicroscopic entities. Andre Luoff, a virologist and Nobel...

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SEXUAL REPORDUCTION IN BACTERIA

In bacteria sexual reproduction is of three types :Transformation : The process of uptake of a complete or fragment of a naked DNA molecule by a competent cell from the medium and incorporation of this molecule into recipient chromosome in a heritable...

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IMPORTANCE AND SCOPE OF MICROBIOLOGY AS A MODERN SCIENCE

Some organisms are very small and can’t be seen with the unaided human eye. Hence these small and invisible organisms is called MICROBIOLOGY.Organism with a diameter of 1mm or less are can’t be seen with the human eye. Hence these organisms are called...

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MICROBES AND THEIR DISTRIBUTION

Microorganisms are widespread and omnipresent. They live in water, air and soil. They also live in side the plants and animals. Microorganisms are widely employed in many industries connected with the manufacture of food, medicines, textiles and chemicals....

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IMPORTANCE OF MICROBIOLOGY

Microorganisms serve as specific agents for large scale chemical transformations, specially variety of geochemical changes. Winogradsky and Beijerink proved that microbes play important role in the Carbon cycle, Nitrogen cycle, Sulphur cycle etc. they...

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HISTORY OF MICROBIOLOGY

The first person who discovered microorganism was a Dutch merchant Anton Van Leeuwenhoek. He named them as animalcules or little animals. Later scientific experiments helped to disprove the theory of spontaneous generation. Lewis Pasteur stated that...

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MUTATION AND MUTAGENESIS

Refers to any heritable change in nucleotide sequence of a gene of the organisms irrespective of altered phenotypic expression of characters of the organisms. A gene codes for a protein, therefore, the physical and chemical properties of proteins...

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GENETICS OF TRANSPOSITION

The genes of transposase and resolvase i.e. tnpR and tnpR are identified by recessive mutations. The above enzymes accomplish the two stages of TnA mediated transposition. Like IS- type elements the transposition stage involves the ends of the elements....

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TRANSDUCTION

The transfer of genetic material from one cell to another by a bacteriophage is called transduction. The phenomenon of transduction was first discovered by Zinder and Lederberg while searching for sexual conjugation in Salmonella species.The infection...

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GENETIC NOTATION

If a bacterial cell synthesizes amino acid leucine, it is represented as Leu+, and if it does not it is denoted as Leu+. The symbol has capitalized (not italicized) the letters. It denotes that Leu- has...

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ORIGIN AND EVOLUTION OF GENETIC CODE

From the discussion of genetic code some important facts came into light as the degeneracy and universality of the genetic code. It may be supposed that present from of genetic code would have evolved...

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GENETIC CODE IN MITOCHONDRIA

Genetic code is universal and does not undergo any change. But during 1980s, it was discovered that the genetic code of mitochondria of yeasts, Drosophila and mammals differs from the universal genetic code. The mitochondrial genome is usually circular...

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GENE MACHINE

Recently, fully automated commercial instrument called automated polynucleotide synthesizer gene machine is available in market which synthesizes predetermined polynucleotide sequence. Therefore, the gene can be synthesized rapidly and in high amount....

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ARTIFICIAL SYNTHESIS OF A GENE FOR BACTERIAL TYROSINE tRNA

In 1975, Khorana and co-workers completed the synthesis of a gene for E.coli tyrosinet RNA precursor. E.coli t RNA precursors are formed from the larger precursors. The tyrosine t RNA precursor has 126 nucleotides. They sunthyesized the complete sequence...

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OVERLAPPING GENES (GENES WITHIN GENES)

In 1940s, Beadle and Tatum proposed one-gene-one protein hypothesis which explains that one gene encodes for one protein. However, if one gene consists of 1,500 base pairs, a protein of 500 amino acids in length would be synthesized. In addition, if...

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SPLIT GENES

During 1970, in some mammalian viruses (e.g. adenoviruses) it was found that the DNA sequences coding for a polypeptide were not present continuously but were split into several pieces. Therefore, these genes were variously named as split genes or introns...

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GENETIC DIVERSITY

There is genetic diversity among the microorganisms. The total number of genes in one microorganism differ from that in the other. For example, bacteriophage R17 and QB consist of only three genes. SV40 contains 5-10 genes. Ecoli consists about 4000...

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REPLICATION Of DNA

one of the most important properties of DNA is that it forms its additional identical copies. The process of forming its replica copy is called replication.Replication is the basis of evolution of all morphologically complexed forms of life. Howard and...

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IMPORTANT FEAUTURES OF GENETIC CODE

Here are some important features of genetic code :1. sixty one codons correspond to amino acids.2. Four codons are the signals. There are three stop codons (UAA, UAG, UGA) and one start codon (AUG). Rarely, GUG also acts as start codon.3. Amino...

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GENETIC ENGINERING

Moreover, for centuries human being have been altering the genetic make up of organisms by selective breeding of plant and animals. The deliberate modification in genetic material of an organism by changing the nucleic acid directly is called genetic...

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ARTIFICIAL SYNTHESIS OF GENE

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GENE REGULATION

The DNA of a microbial cell consists of genes, a few to thousands, which do not express at the same time. At a particular time only a few genes express and synthesize the desired protein. The other genes remain silent at this moment and express when...

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GENE EXPRESSION

The DNA has two important role in the cell, first is replication and the second is expression. Gene expression is accomplished by a series of events. The information contained in DNA is converted into...

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MICROBIAL GENETICS

In prokaryotes the method of cell division differs from that of eukaryotes. No meiosis or mitosis occurs in prokaryotes because of lack of nucleus. In contrast, in prokaryotes and a few eukaryotic microorganisms...

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UNITS OF A GENE

After much extensive work done by the molecular biologists the nature of gene became clear. A gene can be defined as a poly nucleotide chain that consists of segments each controlling a particular trait....

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GROWTH OF MICROBES

Growth is defined as an orderly increase in cellular components. Microorganisms grow in a variety of physical and chemical environments. A number of methods are available for microbial growth. The choice...

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CLASSIFICATION OF BACTERIA

Although the bacterial structures are quite simple but their classification is quite difficult. However, due to readily available devices in the field of molecular biology it make the taxonomy much easy.The...

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MICROBIAL DIVERSITY

The current list of the world's biodiversity is quite incomplete and that of viruses, microorganisms and invertebrates is especially deficient. The fungal diversity indicate the total number of species...

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2009 ·microbiology at a glance by TNB