Some effects of hydrogen ion concentration on trypanosome numbers and infectivity

Abstract

Suspensions of organisms of the Trypanosoma brucei subgroup, adjusted to various pH values between 5.8 and 9.0 and maintained at 0 °−2 ° C, were studied. With preserved (frozen) material: the optimum pH for the maintenance of numbers and infectivity was about 8.0 (at this pH, numbers were little diminished over 24 hours, and infectivity was well maintained for 8 hours); at pH 8.6 and pH 9.0 infectivity was maintained for at least 6 hours, but the numbers of trypanosomes present at 24 hours were less than at pH 8.0; at pH 7.4, although both trypanosome numbers and infectivity were nearly as well maintained as at pH 8.0, there was evidence that pH 7.4 was near the limit of the optimum zone; and at pH values of 7.0 and below, both numbers and infectivity were rapidly and severely reduced. With fresh material: at pH values between 6.3 and 7.8, both numbers and infectivity were well maintained for at least 2 hours; and at pH 5.6 and 5.7, although numbers were maintained for at least 2 hours, infectivity was immediately and severely reduced. The effects found appear to be related specifically to hydrogen ion concentration. The relation between the numbers of trypanosomes in, and the infectivity of, a trypanosome suspension was not necessarily constant.