Blastocladiella emersonii zoospore maintenance factor: A quantitative bioassay used to characterize extracellular appearance and maintenance of factor and interactions between factor, zoospores, and salt

A quantitative bioassay for Blastocladiella emersonii zoospore maintenance factor (ZMF) is documented analyzed. The basis of the assay is an antagonistic interaction between NaCl and ZMF; the former elicits rapid encystment in zoospore populations whereas the latter counteracts this effect. Dilution techniques are used to quantitate the effects of each variable in terms of percentage rapid encystment. Each conditional bioassay variable examined (NaCl concentration, assay pH, cell density, zoospore age, time of assay) appears to affect the sensitivity of zoospore populations to ZMF rather than the level of ZMF activity per se. In particular, zoospore populations "age," in terms of lowered sensitivity to ZMF, in the following ways: (a) "zoospore aging" without NaCl added and either with or without ZMF added; and (b) "delayed encystment" with NaCl and different fixed levels of ZMF added. ZMF activity in the medium (buffered CaCl2) accumulates gradually during sporulation; under bioassay conditions and even at subsaturating levels of ZMF activity, activity recoverable from the medium remains stable over long time intervals (4.5-24 h) whether populations remain zoospores or germinate. Populations incubated without added ZMF, whether they remain zoospores or germinate, do not detectably release ZMF activity into the medium. We discuss the following proposals concerning the functions of ZMF: (a) ZMF acts as a negative regulator of the mechanics of zoospore encystment; and (b) ZMF acts as a self-generated, natural dispersal signal for the organism. © 1981.

Duke Scholars

Author William Kirby Gottschalk Neurology, Behavioral Neurology