GENETICAL CHARACTERS 11-4 



ROUGH COLONIES 



The "roughness" of colonies grown of solid medium is a diag- 

 nostic character differentiating various haplophase cultures. Smooth- 

 ness is characteristic of the diplophase when grown on agar. Winge 

 and Laustsen have shown that diplophase colonies grown on gelatin 

 at low temperature produce rough colonies with characteristic mor- 

 phological topography, but our cultures were grown on agar at room 

 temperature and under these conditions, diplophase cultures are 

 smooth. The smooth characteristic of the large-celled diplophase 

 depends on the fact that the daughter cells separate quickly from 

 mother cells and each new unit falls evenly into place, making the 

 colony smooth. The contrast between the large-celled diplophase 

 smooth cultures and the small -celled haplophase rough cultures 

 probably depends primarily on cell size, for it appears as if the 

 smaller cells tend to cohere in clusters much more readily than 

 the larger ones. The difference in the types of aggregates charac- 

 teristic of diplophase and haplophase cells makes it difficult to re- 

 late the colonial characteristics of the diplophase culture to its hap- 

 lophase progeny, and since cell aggregation is so closely related to 

 cell size, haploid colonies must be compared to other haploid colo- 

 nies and diploids to other diploids. Roughness of the haplophase 

 culture is due to the fact that the smaller cells remain together in 

 clusters in such a way that a definite pattern results when the colony 

 reaches its full growth. The basic pattern of aggregation is ob- 

 servable in microscopic examination of the cells from broth cul- 

 tures, for rough types generally bud in various "rosette" forms. 



Winge (1935) has described the "figure 8" arrangement of hap- 

 loid cells prior to homozygous copulation. After a bud has reached 

 full size, two new buds appear (one from the mother and one from 

 the daughter cell) near the point of union of daughter and mother 

 cell, producing a "4 -leaf clover" effect. Most "rosettes" originate 

 in a variation of the "figure 8" formation without the subsequent copu- 

 lations. Many of these cultures make what appears to be homo^^ene- 

 ous suspensions because the "rosettes" are too small to affect the 

 turbid appearance produced when the culture is suspended in fluid 

 medium or grown on broth, but the extremely rough colonies cannot 

 be brought into a homogeneous suspension, and when extreme rough- 

 type yeasts are grown in liquid medium, the supernatant liquid is 

 completely clear. This is a character much desired for beer and 

 wine yeasts, especially for champagne yeasts. Such yeasts are 

 called "bottom" yeasts. There is a basic pattern of cohesion even 

 in extremely smooth cultures, for nearly all colonies show some 

 distinctive topographical structure if grown on solid medium long 

 enough to form a giant colony. Conversely, when moderately rough 

 colonies are sown heavily enough on agar to prevent the formation 

 of large colonies, only smooth ones appear. On an unevenly spread 



