Ernst Jarosch runs his hand gently over the brownish piece of fabric, which peeks out from its aluminum packaging. It looks a bit tattered and is worn out in several places around the edges. “Our velvet pads are regularly cleaned and autoclaved – and that takes its toll,” says Ernst, a scientist on Thomas Sommer’s research team. It’s quite possible that the velvet pads used in his laboratory are among the oldest lab equipment at MDC. Corinna Volkwein, a technical assistant on the research team, bought the velvet some 24 years ago at a local fabric store.
The scientists and his colleagues use the velvet pads to transfer micro-organisms from one culture medium plate to another. These plates are growing yeast colonies whose genes differ from each other. If a colony has a particular gene, it can grow on some culture media but not on others. Such a gene, for example, can make the yeast resistant to a specific antibiotic. When researchers add this antibiotic to the medium, only yeast with the resistant gene can grow there.
During the experiment, researchers first cross yeast with various genetic characteristics and then compare the growth of the colonies on culture plates containing different additives. This is where the soft fabric comes into play. “Velvet is well suited for this purpose because it has a coarse surface to which the cells stick, allowing them to be transferred to the next plate. This is much faster than testing everything separately,” says Christian Lips, a PhD student on the research team. He stamps a plate containing yeast colonies onto a velvet-covered plastic block of the same size. He then presses several sterile culture medium plates against the imprinted velvet. These plates now show a fine, but clearly visible imprint of yeast cells. By observing the growth behavior on these plates – are the colonies exhibiting good growth or not growing at all? – Christian can make deductions about the genotype, that is, the combination of the examined genetic characteristics.
Not every type of velvet is suitable for laboratory use: When Ernst Jarosch purchased new fabric several years ago, he soon discovered that its quality was not good enough. The new velvet gave off lint and was quickly pulled from use. Luckily, the tried and tested velvet is still holding up, and – who knows? – maybe for another 24 years.
Contribution pictures: Editorial team, MDC