432 PHYSIOLOGY OF THE FUNGI 



cosmopara vasinfecta, Phoma bctae, Septoria nodorum, Sordaria fimicoia, 

 Sphaeropsis malorum. 



EXERCISE 9 

 Vitamin Deficiencies in the Fungi 



This exercise is oiithned to demonstrate (a) vitamin deficiencies in the 

 filamentous fungi, ih) the differences in the needs of the different species 

 of fungi, (c) the techniques used to determine these deficiencies. For a 

 discussion of vitamin deficiencies and lists of vitamin-deficient fungi, see 

 Chap. 9 and Robbins and Kavanagh (1942). 



In studying the vitamin requirements of the fungi, great care must be 

 taken to use glassware and chemicals which are free from vitamins. The 

 glucose-asparagine medium has the advantage of being a suitable source 

 of carbon and nitrogen for most fungi. Casein hydrolj'sate may be used 

 in the place of asparagine. In its preparation, the medium should be 

 boiled with activated charcoal (Norit, 5 g. per liter), to remove any 

 vitamins present, and filtered. Thus, the medium is "essentially free" 

 of vitamins. Contamination may occur from dust, cotton fibers from the 

 plug, dirty glassware, etc. Micro essential elements and vitamins must 

 be added after this treatment. 



Media. It is best to use litiuid media for this exercise so the mycelium 

 can be dried and weighed. 



46. Basal glucose-asparagine (vitamin-free) 



47. As above, with thiamine (100 yug per liter) 



48. As above, with biotin (5 ng per liter) 



49. As above, with thiamine and biotin 



50. As above, with thiamine, biotin, inositol (5 mg. per liter), and pyridoxine (100 pg 

 per liter) 



Adjust the pH to 6.0 and distribute to tubes or flasks (25 ml. per 250-ml. 

 flasks or 15 ml. per 125-ml. flasks) before autoclaving. 



A. Screening test for vitamin deficiencies. Simple screening tests to 

 determine roughly the deficiencies of fungi may be carried out in either 

 liquid or purified-agar (see Ex. 1) media. Test tubes may be used for 

 agar media, but Erlenmeyer flasks are suggested for liquid media. The 

 student should select four or five species from the stock-culture collection, 

 and inoculate tubes or flasks of each of the above media, in triplicate, 

 with each species. Either spores or a small bit of mycelium may be used 

 as inoculum. Daily observations and records of growth should be made. 

 Visual estimates of relative amounts of growth are sufficiently accurate 

 to detect most deficiencies. If liquid media are used, the mycelium may 

 be weighed. 



B. Growth curves of vitamin-deficient fungi. Inoculate 10 flasks each 

 of media 46 to 50 with a filamentous fungus shown in part ^4. to be defi- 



