DAIRY BACTERIOLOGY 



The size of microorganism is given in micromillimetres, or 

 microns, designated by the Greek letter /z, being one-thousandth 

 part of a millimetre. Bacterial cells generally measure from 

 0-5 to 2 JJL in thickness. Some idea of their minuteness may be 

 formed on consideration of 

 the fact that the space of 

 a cubic millimetre will hold 

 one thousand million bac- 

 teria of average size. From 

 Figs. 1, 2 and 3 it will be 

 seen that the cells of yeasts 

 and moulds are from five 

 to ten times as large as 

 those of the bacteria. V^ \ \W V V 



FIG. I. Acetic Acid Bacteria (Bac- 

 terium aceli). (After Hansen.) 



FIG. 2. Brewers' Yeast (Saccharomyces 

 cerevisice). (After Hansen.) 



All magnified 1,000 times (x 1,000). 



FIG. 3. Penicillium glancum. 



GROWTH AND REPRODUCTION 



Under normal conditions a bacterial cell will soon grow to its 

 maximum size, often becoming more or less elongated in form, 

 when a cross partition appears dividing it transversely into two 



