Freeze-drying of microbial cultures (Ten ampoules)
One of the best ways to store bacterial, fungal, yeast or other microorganism culture for long periods of time is to use a process called freeze drying or lyophilisation. In the freeze-drying process water is removed from the frozen sample. Bacteria are suspended in a suitable protective medium, frozen and exposed to a vacuum. After drying the bacteria are stored under vacuum in glass vials, for preservation of culture collection. The viability or the colony forming units of the strain are tested before and after the preservation step and, depending from the strain, in certain intervals during the storage period for documentation of viability form.
Determination of G+C mol content (Tm)
GC-content (Guanine-Cytosine content), in molecular biology, is the percentage of nitrogenous bases on a DNA molecule which are either guanine or cytosine .This may refer to a specific fragment of DNA or RNA, or that of the whole genome. When it refers to a fragment of the genetic material, it may denote the GC-content of part of a gene (domain), single gene, group of genes (or gene clusters) or even a non-coding region. G (Guanine) and C (Cytosine) undergo a specific hydrogen bonding whereas A (Adenine) bonds specific with T (Thymine).
The GC-content percentages as well as GC-ratio can be measured by several means, but one of the simplest methods is to measure is called the melting temperature of the DNA double helix using spectrophotometry. DNA melting can be easily followed spectrophotometrically because of the absorbance of 250 nm UV light by the DNA increases during strand separation. When a DNA sample is slowly heated the absorbance increases as hydrogen bonds are broken and reaches a plateau when the entire DNA has become single stranded. The midpoint of the rising curve gives the melting temperature, a direct measure of the G+C content.
GC content is usually expressed as a percentage value, but sometimes as a ratio (G+C ratio or GC-ratio).
Bacterial Genomic DNA (on request)
The isolation and purification of DNA from cells is one of the most common procedures in contemporary molecular biology and embodies a transition from cell biology to the molecular biology (from in vivo to in vitro). The organism to be used should be grown in a favourable medium at an optimal temperature, and should be harvested in late log to early stationary phase for maximum yield.
The genomic DNA isolation needs to separate total DNA from RNA, protein, lipid, etc.