96 Microbes and You 



actions. There is little doubt that a number of forces are active 

 in the process, and to try to pinpoint a single explanation is prob- 

 ably not feasible. 



NUCLEUS 



A typical cell contains a nucleus, usually rather spherical in 

 shape, enclosed within a thin membrane, and surrounded by ma- 

 terial called CYTOPLASM. But bacteria, just to be different, do not 

 usually possess a well-defined nucleus such as we observe in most 

 other cells. Among other things nuclear material consists of 

 CHROMATIN, a substaucc believed to be vital to all living cells. The 

 name chromatin is derived from the strong affinity it has for certain 

 coal-tar dyes, and the nucleus of cells stains more deeply than other 

 parts of the protoplasm. 



Some investigators go so far as to claim that the primitive 

 nature of bacteria makes a well-defined nucleus unnecessary, but 

 others hold the opposite view, and they claim that a bacterial cell 

 is extremely complex. They feel that it has to be, in order to cope 

 with all of the life processes within the borders of a single cell. 

 The nucleus is the heart of the cell— the control panel of a complex 

 mechanism. 



A nucleus is usually considered to be the determiner of heredi- 

 tary characteristics, and to some persons the nucleus is a single 

 chromosome which must undergo division before new cells can be 

 formed. If each offspring is to resemble the parent cell, there 

 must be some mechanism for the transmission of these hereditary 

 characteristics, usually a function of chromatin material. 



When we subject bacteria to nuclear dyes, the entire cell be- 

 comes stained, suggesting that the nuclear material may be diffuse. 

 There is some evidence to support the concept that at certain stages 

 in the growth of bacteria the nuclear material may undergo a local 

 concentration. 



Common beliefs relative to the bacterial nucleus include the 

 following: 



1. The entire bacterial cell is composed of nuclear material, with 

 little or no cytoplasm. 



