A Bacterium That Acts Like a Toothbrush

Researchers have identified a new ally in the war against tooth decay: an enzyme produced by a mouth bacterium that prevents plaque formation. The finding could eventually lead to the development of toothpaste that harnesses the body's own plaque-fighting tools.The human mouth is awash with bacteria. More than 700 species thrive in the hot, moist conditions, including Streptococcus mutans, one of the main components of plaque. Clinging to the teeth in thin layers called biofilms, S. mutans digests sugars and produces acids that can eat into enamel and cause cavities. Other bacteria are more gracious guests. In 2009, for example, scientists found that S. salivarius, a type of bacterium found on the tongue and other soft tissues in the mouth, decreases the buildup of S. mutans biofilms.Hidenobu...

Read more »

Posted in: Microbiology

SUSPENSION CULTURE

Individual cells or cell aggregates dispersed and growing in moving liquid media is known as suspension culture.Explants used in suspension cultureIn regular practice suspension culture is initiated by transferring piece of undifferentiated and friable cells to a liquid medium which is continuously agitated by a rotator shaker.Suspension cultures have also been started from sterile seedlings or imbibed embryos or leaves. Leaves and other tissues can be gently grinded using homogenizer. This homogenate containing living cells, dead cells and cell debris is cleared by filtration and centrifugation and then transferred to a liquid medium. This is the mechanical methodIn enzymatic method, pectinases (enzymes which digest pectin cell wall) are used for isolation of single cells.Method At first...

Read more »

SOMACLONAL VARIATION

Somaclonal variation is defines as the genetic variability present among cultured somatic cells.Plants derived from such cells or progeny of such plants are called somalcones.The term somaclonal variation was first used by Larkin and Scowcroft in 1981.Somaclonal variations can be selected for disease resistance, improvement of nutritional quality, adaptation of plants to stress conditions, resistance to herbicides etc.Somaclonal variation has been observed in plants such as apple, sugarcane, potato, tomato etc.PROCEDURE FOR ISOLATION OF SOMACLONAL VARIANTS Isolation of somaclonal variants can be grouped into two broad categories. They are:1....

Read more »

Posted in: Biotechnology

MICROPROPAGATION

Generally plants propagate by sexual and asexual methods.Sexual method: here fertilization of ovary taken lace pollen grains and the resulting plants show high degree of heterogenecity.Asexual Methods: here the cells undergo mitosis and the resulting plants will be genetically identical to parents.Multiplication of genetically identical copies of plants is known as clonal propagation.Clonal propagation of plants through tissue culture is known as Micropropagation.Explants (starting material used to initiate tissue cultureThe explants widely used for tissue culture includea) Meristemb) Shoot-tipc) Auxiliary buds a) MeristemThis is the terminal portion of shoot tip containing a group of actively dividing cells.b) Shoot-tipShoot-tip/ shoot apex also contains a group of actively dividing cells...

Read more »

Posted in: Biotechnology

Chemical composition of eukaryotic chromosome

The eukayotic chromosome is composed of DNA, basic proteins called histones, non-histone proteins(involved in transcription, replication, repair and recombination of DNA) and RNA . The histone proteins are basic proteins rich in arginine and lysine. They are of 5 types-H1, H2A, H2B, H3 and H4.Eight molecules two each of H2A, H2B, H3 and H4. From an ellipsoid core (11nm long and 6.5-7nm in diameter) around which about 147-166bp of DNA coils in 13/4 turns. This DNA histone complex is called nucleosome, the building block of chromosome, the building block of chromosome found as repeating units. The nucleosomes appear as a string of beads in the chromatin. About 14-100bp of DNA between these beads forms the LINKER region.The hsitone H1 associates with the linker to aid folding of DNA into a more...

Read more »

Posted in: Microbiology

Chromosome of Cyanobacteria

The DNA in cyanobacteria is organized into a complex helical and folded structure and is distributed uniformly throughout the cytoplasm. It is likely that DNA is associated with histone like proteins and RNA. The size of the genome varies widely in cyanobacteria with molecular weight ranging between 1.6x109 and 8x109 daltons. Most of the unicellular cyanobacteria possess genomes of about 1.6x109 – 2.7x109 daltons. Filamentous cyano bacteria how ever have larger genomes.Viral GenomeThe core of the virion is made up of nucleic acid, either DNA or RNA never both. Four types of nucleic acid are formed in viruses with reference to number of strands. They formed in viruses with reference to number of strands. They are: 1- Single stranded DNA ( ssDNA) Eg.Ø X 1742- Double stranded DNA (dcDNA) Eg....

Read more »

Posted in: Microbiology

CHROMOSOME

v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable...

Read more »

Posted in: Microbiology