OLIGOSACCHARIDES 67 



source of carbon for fungi but is not so nearly universally available 

 as maltose. Thus, of 57 fungi studied by Lilly and Barnctt (116) only 

 4 were completely unable to utilize sucrose, but several grew slowly 

 with it. Among the major groups of fungi, failure to utilize sucrose 

 appears to be particularly common in the Chytridiales (Table 1) and 

 the Mucorales (174), less common in other groups. Actinomycetes 

 rarely, if ever, utilize sucrose (13, 221). 



Lactose, the /3-galactosido-glucose of mammalian milk, is used by 

 far fewer fungi than any of the disaccharides so far mentioned, and 

 may be characterized as a poor carbon source (61, 116). At least some 

 actinomycetes grow with lactose (40, 51, 215). Adaptation to lactose 

 occurs among fungi (p. 87), and whether or not an organism is re- 

 ported as able to utilize the sugar often, therefore, depends on the 

 length of the incubation period chosen. 



Melibiose, an a-glycoside, has not been investigated often; the few 

 data available (Table 1) indicate that it is not utilizable by many 

 fungi. Data for gentiobiose are similarly too limited to allow general- 

 ization. Growth on amygdalin, the /^-glycoside of gentiobiose, by 

 aquatic fungi (17) presumably indicates gentiobiose utilization. 



Raffinose attacked at one linkage yields galactose and sucrose, at- 

 tacked at the other yields fructose and melibiose. From the limited 

 data of Table 1 and the more extensive studies of Lilly and Barnett 

 (116), it would appear that the majority of fungi utilize raffinose, but 

 that non-utilization is common. Some doubt is raised with regard to 

 raffinose utilization by the finding (18) that raffinose supports growth 

 of Phymatotrichum omnivorum if autoclaved but not if sterilized by 

 alcohol treatment; a reinvestigation of this problem by comparing 

 filter-sterilized to heat-sterilized raffinose may show that raffinose is 

 broken down by autoclaving at least to the extent that some simple 

 sugars are available to initiate growth and to permit, therefore, the 

 formation of adaptive enzymes which then hydrolyze the unchanged 

 raffinose. 



The utilization of an oligosaccharide is believed to be preceded by 

 and dependent on its conversion to hexoses or, possibly, hexose phos- 

 phates. The evidence for this generalization may be summarized: 



1. Fungi that can use a disaccharide possess enzymes which hydro- 

 lyze it (17, 79). An organism which grows on sucrose, for example, 

 proves on examination to form sucrase. Formation of the enzyme is 

 not, however, a sufficient condition for utilization — a mutant of 

 Neurospora crassa produces lactase (/3-galactosidase) but does not 

 grow with lactose as sole carbon source (112). 



