Changes in the rate of chitin-plus-chitosan synthesis accompany morphogenesis of Mucor racemosus.
The in vivo differential rates of chitin-plus-chitosan biosynthesis in Mucor racemosus were determined under a variety of conditions, leading to yeast cell or mycelial morphology. Chitin-chitosan was determined as hot NaOH-insoluble radioactivity derived from N-acetyl-D-[1-3H]glucosamine in the medium. Control experiments demonstrated that the labeled material possessed the properties of chitin-plus-chitosan. Our results indicate that Mucor yeasts have a relatively low differential rate of chitin-plus-chitosan synthesis and that mycelial cells have a threefold-elevated differential rate. Treatment of aerobic cells with exogenous N6, O2-dibutyryl cyclic adenosine 3',5'-monophosphate, an agent which induces yeast cell morphology, also results in a lowered rate of chitin-plus-chitosan synthesis. Control experiments eliminated the possibility that the observed rate changes were due to changes in endogenous pool size, uptake of exogenous N-acetyl-p-[1-3H]glucosamine, or alterations in growth rate. Therefore, the changes are seemingly linked to morphogenesis. These results strengthen the idea that cyclic adenosine 3',5'-monophosphate plays an important role in dimorphism in Mucor. In addition, pulse-chase experiments suggest that considerable modification of newly synthesized chitin plus chitosan in both yeast cells and mycelia occurs in vivo.
D000332:Aerobiosis; D000693:Anaerobiosis; D002686:Chitin / Q000096:biosynthesis*; D048271:Chitosan; D009024:Morphogenesis; D009089:Mucor / Q000166:cytology / Q000378:metabolism*; D011134:Polysaccharides / Q000096:biosynthesis*
D011134:Polysaccharides; D002686:Chitin; D048271:Chitosan