MORPHOLOGY 





absorption of water by the outer layer of the cell wall seems to 

 be responsible for the gelatinous secretion. The term zooglcea 

 is applied by bacteriologists to these masses of bacteria and 

 gelatinous material, e.g. B. vulgatus. This formation is 

 noted on the surface of solid and liquid nutrient substances. 

 The gelatinous material secreted is similar to that which 

 forms the capsules of certain species of bacteria (Fig. 27). 



It composes a thick cover- 

 ing on the outside of the 

 bacterial chains. This 

 formation is very often seen 

 in the processes of fermen- 

 tation of Streptococcus 

 mesenterioides in sugar 

 vats. Other clumps of bac- 

 teria which are not readily 

 soluble in water and which 

 arise from fusion or imper- 

 fect separation of the individual cells are often seen. These 

 masses are called pseudozooglcea. They do not possess the 

 compactness and gelatinization of the true zooglcea. Zooglcea 

 and pseudozooglcea masses compose the so-called slime which 

 collect on various fluids. In nutrient liquids certain bacteria 

 form aggregates producing the appearance of scum on the sur- 

 face, e.g. B. subtilis. These aggregates are sometimes called 

 pellicles. The pellicle usually grows until it covers the surface 

 of the liquid. They contain, in addition to the bacteria and 



FIG. 27. Zoogloea in an aquatic bacte- 

 rium. The individual cells are thickly 

 aggregated at the periphery, less so in 

 the middle; they are held together by 

 a mucus-like secretion. After Fischer. 



