Effect of Sodium Chloride, Dulcitol and Glucose on the Growth of Proteus in Shaken and Static Broth Cultures

Abstract

IT has recently been reported that Proteus is unique among Gram-negative bacteria of non-marine origin for possessing an ability to grow in the presence of high salt concentration¹. Crisley² showed that a strain of Proteus vulgaris grown in the presence of sodium chloride utilized more glucose and grew to a greater extent than when grown in the absence of sodium chloride. It has now been found that, not only does Proteus possess a high sodium chloride tolerance, but also gradually increases in growth when grown in broth cultures containing rising concentrations of this electrolyte. Furthermore, the addition of rising concentrations of either dulcitol or glucose to the broths has a similar effect on the growth of Proteus to that produced by the addition of sodium chloride, but it is of a lower order. When Proteus is grown in broths containing the same range of concentrations of sodium chloride, dulcitol and glucose, but which are agitated, an enhancement of growth occurs (compared with growth obtained in static culture), except for those cultures grown in broths containing glucose. This effect has been discovered as a result of experiments undertaken to elucidate the reasons for the formation of discrete colonies of Proteus on a solid medium consisting of the broth used above solidified with agar. Dulcitol was chosen because it is not fermented by Proteus, thus affording an ‘inert chemical’ the presence of which only exerted physical effects (Figs. 1, 2 and 3).