Produkt des Monats: Juli 2021
Was wäre die Mikrobiologie ohne Agar?
Mikrobiologische Nährböden werden erst durch Agar zu dem, was sie sind.
Nämlich fest! Gewonnen wird das Naturprodukt aus Rotalgen.
Chemisch handelt es sich beim Agar um eine Mischung der Polysaccharide Agarose und Agaropectin. Agar bietet alles, was man sich von einem Geliermittel wünscht: Er macht den Nährboden fest und geschmeidig, er ist temperaturbeständig (sprich, er schmilzt nicht bei höheren Inkubationstemperaturen von >40°C) und er wird von Bakterien und Pilzen nicht verstoffwechselt.
From fruit jelly to the Petri dish
Agar was discovered as a perfect gelling agent for microbiology by Fanny Hesse in 1881. She was the wife of the microbiologist Walther Hesse, who was working on the isolation of various bacteria as an employee of Robert Koch. As chance would have it, Fanny came into contact with the gelling agent, which was still unusual in Europe at the time, through acquaintances and was already using it in the kitchen as a heat-resistant alternative to gelatine. Well informed about the positive properties of agar, she helped her husband on his way – and ultimately made a significant contribution to Robert Koch’s success in isolating the tuberculosis pathogen in 1882.
Another positive aspect in today’s world: agar is vegan, whereas gelatine is hydrolysed collagen from the connective tissue of animals (usually obtained from cattle and pigs).
Agarose, as used for gel electrophoresis, is the purified form of agar. It consists only of the linear, gellable agarose polysaccharide.
