except that the chromosomes are arranged with the long axis parallel to 

 the spindle. Under anaerobic conditions. Subramaniam claims that endo- 

 polyploidy occurs. These claims have been denied by a number of work- 

 ers, including Winge (1951) and Lindegren and Rafalko (1950), who 

 disagree with Subramaniam's identification of the nucleus. 



Turian and Cantino (1960) have described mitotic divisions in the 

 water mold, Blastodadiella. In this organism what appears to be the 

 nucleus consists of a vacuole, almost completely filled with a nucleolar- 

 like body and surrounded by a dense ring of chromatin. During division, 

 the chromatin becomes organized into two opposing crescents which 

 then separate to give an anaphase-like configuration with the nucleolar- 

 like body serving the purpose of a spindle (Figure 10-2). 



Another class of organisms in which disputes concerning nuclear or- 

 ganization and division have generated more fire than light, is the bac- 

 teria. DeLamater (1951) described nuclear division in several bacte- 

 ria in terms which made the process sound virtually identical with that 

 in other organisms. Bisset (1951) among others hotly contested De- 

 Lamater's conclusions. Again the argument centers around the identifica- 

 tion of cell parts rather than around the premise of '"typical" division. 



The blue-green algae (Cyanophyta) have long been considered by 

 phycologists to have no organized nuclei or chromosomes in the usual 

 sense, though chromatin bodies have been described. In 1960. Leak and 

 Wilson described "mitotic-like" divisions in the filamentous Anubaena 

 variabilis after staining by the Feulgen technique. According to their 

 description, there is no central nucleus but, instead, a number of vacuoles 

 partially surrounded by Feulgen-positive material. Recently, the absence 

 of a typical nuclear boundary has been confirmed by electron micros- 

 copy. During division, the vacuoles break down and the chromatic ma- 

 terial is distributed through the cell in the form of thread-like bodies. 

 Ultimately, the chromatic material separates into two anaphase-like 

 groups and the cell cleaves (Figure 10-3). Subsequent to their published 

 observations, occasional metaphase-like groupings have been noted. No 

 spindle has so far been seen, but the techniques used are not suitable 

 for revealing the achromatic apparatus. In contrast, green algae such as 

 Spirogyra appear to have typical mitotic divisions (Figure 10-4). 



Though many more studies need to be made on microorganisms, it 

 would seem that the organization of genetic material in interphase cells 

 is subject to considerable variation, including complete lack of a double- 

 membraned nuclear boundary. If we exclude the viruses, actual division 

 of the chromatin appears to be somewhat similar in all organisms, 



REPLICATION OF GENETIC MATERIAL IN MICROORGANISMS / 205 



