Early events of cell differentiation in Naegleria gruberi. Synergistic control by electrolytes and a factor from yeast extract☆

[摘要] ForamoebaeofNaegleriagruberiNEG-Mgrowinginanaxenicmedium,onecomponentofthemedium,yeastextract,controlswhetherphenotypictransformationintoflagellatesoccurs.Fractionationoftheyeastextractyieldedtwocomponentsthatcontroltransformation:electrolytesandanunidentifiedFactor.Electrolytespreventtransformationifpresentaboveacertainconcentration.ForNaClandKCl,forexample,thecriticalconcentrationis0.08M.Theeffectisnotspecifictoparticularions,norisitduesimplytoionicstrength.Osmoticpressureproducedbynonpenetratingnonelectrolyteslikesucrosecanalsoinhibittransformation,buttheeffectofelectrolytesisnotduesolelytoosmoticpressure.TheunidentifiedFactor,asmallmolecule,probablyaromatic(adsorbsreversiblytocharcoal),canpreventtransformationataconcentrationthatdoesnotincreasetheosmoticpressureofthesolution,andthatisestimatedtobenotmorethan0.001M.TheactionofFactorincontrollingtransformationismuchpotentiatedbyelectrolytes,suchthatacombinationofone-eighththeelectrolyteconcentrationneededtopreventtransformationwithone-fourththeFactorconcentrationcompletelypreventstransformation.ThesynergisticactionwithFactorisnotspecifictoaparticularion,buttherearedifferences.Forexample,Na+ismuchmoreeffectivethanCs+.Factorandosmoticpressuredonotactsynergistically.AmoebaegrowninthepresenceofextraFactoradapttoit,andwilltransforminconcentrationsofFactorandofelectrolytethatpreventtransformationofunadaptedcells.Theseadaptedcellsalsocantransforminregulargrowthmedium.ItisconcludedthatFactorandelectrolytesareinvolvedinthenormalcontroloftransformationoftheseaxenicNaegleria.Theresultsprovideastartingpointforstudyingearlyeventsinthiscelldifferentiation.

[学科分类] 生物科学（综合）