Nurse growth

from Wikipedia, the free encyclopedia
Nurse growth of Haemophilus influenzae: Staphylococcus aureus (thick vaccination line in the middle) and Haemophilus influenzae (fine colonies around vaccination line)

As Ammenwachstum , synonymous as Ammenphänomen or satellite growth , growth is the bacterium Haemophilus influenzae referred when he takes on blood agar plates can only grow with the help of a second type of bacteria.

Unlike cooked blood agar, blood agar plates still contain complete erythrocytes . Haemophilus influenzae bacteria can only grow in the vicinity of these cells if these are broken down ( hemolyzed ) by another type of bacteria and the growth factors contained in them get into the medium . One such hemolytic strain, which is then referred to as “wet nurse”, is Staphylococcus aureus , for example . It secretes hemolysins into the agar, which lyse the erythrocytes of the blood agar and release hemin (= factor X). They also release NAD ( nicotinamide adenine dinucleotide ) (= factor V) into the agar. These growth factors, NAD and hemin, are essential for Haemophilus . Therefore Haemophilus only grows in the immediate vicinity of its "wet nurse".

The normal cultivation of Haemophilus takes place on agar with the addition of the two growth factors.

A similar phenomenon occurs when, for example, Escherichia coli with an ampicillin resistance grows in medium containing ampicillin . The resistant bacteria are able to produce an enzyme ( beta-lactamase ) that renders ampicillin harmless to them. They add this enzyme to the medium. If the agar plate is stored for a longer period, small satellite colonies also appear around the resistant colonies, which are actually not resistant, but are also protected from ampicillin by the beta-lactamase produced by the neighboring colony.

Individual evidence

  1. a b H. Hof, R. Dörries: Duale Reihe Mikrobiologie , 4th edition, Thieme Stuttgart 2009, S, 419.