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5.9.3 Vegetable Tissue Culture Formulations
ОглавлениеAgar provides a good solid base as a medium in tissue culture techniques. Agar was primarily used as a medium in the development of orchid clones. Since agar media is autoclavable and can be sterilized easily, it can be easily used in plant tissue culture to produce identical virus-free plants also known as monoclonal culture. Generally vegetative parts of plants are grown in agar medium, enriched with adequate chemical nutrition like vegetative hormones such as auxines and cytokines. As the adequate plant growth has been developed, under sterile conditions, these plants are transferred into their respective wild fields/areas.
Table 5.4 Different types of agar medium with respective uses and description.
| Type of agar | Their brief description and uses |
| XLD agar | Xylose lysine deoycolate is an agar with two markers. Suppresses the growth of Gram-positive bacteria and promotes growth of Gram-negative bacteria. Uses in fecal culture. Lactose fermenting bacterial colonies appear yellow in it. |
| Blood agar | An almost complete nutrient-rich media, prepared from animal blood. Supports most bacterial growth. |
| Tryptic soy agar | Provides basic medium to culture several types of microbes. Primarily used as initial growth medium to monitor colony morphology. |
| Chocolate agar | Made from sheep blood, that gives X and V factors, which are important for Haemophilus growth. A nutritional medium for fastidious microbes like Neisseria and Haemophilus species. Conversely, it doesn’t provide haemolysis data of microbes, so species differentiation among the members of Haemophilus are carried out separately. |
| Thayer-Martin agar | Similar to chocolate agar, designed to isolate Neisseria gonorrhoeae aka gonococcus. A Gram-negative bacterium which causes gonorrhoea. |
| LB (Luria Bertani) agar | A counterpart of nutrient agar. Broadly used for isolation of unknown microbes. Doesn’t allow over lapping of microbial colonies. |
| Sabouraud agar | Primarily used in fungal culture at low pH. Lower pH also eliminates most of the bacteria. Encloses gentamicin, an aminoglycoside antibiotic. Gentamicin helps in treating bacterial infections, especially Gram-negative infection. |
| MacConkey agar | An agar, prepared in such a way that it only supports Gram-negative bacterial growth. Already encloses pH indicators. For example: Escherichia coli colonies reflect red colour as a pH indicator. MacConkey agar comes in two types: with sugar lactose and without sugar lactose. As E.coli ferments sugars into acids and gives red colour due the presence of pH indicator, one can actually add desired sugar into ‘sugar free’ MacConkey agar and predict desired microbial colony. |
| Nutrient agar | Supports the largest number of microbial growth of bacteria and fungi. Still very uncertain for many bacteria, it is overly nutritional for some bacteria and deficient for some bacteria, at the same time. Beef extracts and yeast are the nutritional components of this agar. |
| Miller’s LB agar | Miller’s LB agar is a counterpart of Luria Bertani agar. It has the same ingredients as LB agar, but the quantity is different. |
| Non-nutrient agar | Non-nutrient agar is used for the culture of microbes other then bacteria. |
| Neomycin agar | As the name suggests, neomycin agar contains neomycin. Since neomycin is an antibiotic, it checks the growth of certain type of bacteria, in this case, the Gram-negative bacilli and staphylococci. Streptococcus bacteria grow in this agar, more abundantly. Ukrainian-American microbiologist Selman Waksman discovered neomycin in 1949. He extracted it from Streptomyces fradiae bacteria. |
