The Influence of Surface Tension on the Growth of Bacteria

Abstract

A report to the Medical Research Council.- (Received September 5th, 1923.) ONE of the factors which may be anticipated to affect the growth and metabolism of bacteria is surface tension.The relation of this physical factor to other biological problems such as muscle action or the deposition of salts in plant cells [Macallum, 1911] has been the subject of much study; the relation to bacterial growth has received little attention.If, however, one considers the results obtained with surface films by J. J. Thomson [1888] and others it is evident that the increased concentration of substances, such as peptone, at the air/liquid interface ought to have a pronounced effect on those organisms growing at the surface. This should especially be the case with micro-organisms like C. diphtheriae where experience has shown that efficient toxin production is associated with good pellicle formation.In a study of certain factors affecting toxin production my attention was drawn to this aspect of the subject by the statements of practically every -bacteriologist who has worked in this field as to the necessity of removing all but inevitable traces of fat from the medium before it is used. The fact that pellicle is also essential would appear to be connected with the particular conditions of the air/liquid interface.In a paper published in 1919 Larson, Cantwell and Hartzell [1919] made some very interesting statements regarding the effect of lowering the surface tension of media on the growth and habit of bacteria. The protocols of their experiments are unfortunately lacking in details of the methods used for determining surface tension. On lowering the surface tension of their media they observed that anaerobic bacteria grew in the presence of air, that organisms, usually forming pellicles, grew throughout the liquid and did not form a film and that spore-bearing organisms no longer produced spores. Evidently the unusual environment of the bacteria completely changed their habit of growth.

Surface Active Agents and Their Application in Bacteriology

“…Growth of Mycobacterium tuberculosis, human type, was inhibited at surface tensions of 42 dynes/cm while the avian type and Mycobacterium phlei were inhibited at surface tensions below 30 dynes/cm (2). Bacteria flourishing in the gastrointestinal tract seem to be resistant to the deleterious action of surface active compounds in their culture media (127, 218,245). The following order of sensitivity of growth to depression of surface tension has been determined by Wolf (245).…”

The behaviour of crystals and lenses of fats on the surface of water. Part I.—The mechanism and rate of spreading

“…An apparatus similar in design to that described by Wolf (12), whose paper should be consulted for details of calibration, was used. A diagrammatic representation is given in fig.…”

The destruction of rennin by agitation: A case of catalysis at an air-liquid interface

“…The determinations of surface tension were made with the apparatus described recently by Wolf (24). In almost all cases the surface tension of the shaken solution was higher than that of the unshaken, a temporary rise, due to the abstraction of capillary active substances by the foam, and a permanent one due to a chemical reaction between capillary active materials occurring at the surface.…”