142 MICRO-ORGANISMS AND FERMENTATION. 



7. Slime-forming Bacteria. 



Among the various species of slime-forming bacteria there 

 are several which are of peculiar interest in the fermentation 

 industries, as they occur in wine, milk, beet juice, and fer- 

 menting wort, causing morbid changes. By analogy, this 

 slime formation, which usually consists of substances re- 

 sembling gum, may be regarded as a phenomenon closely 

 related to the commonly occurring zooglcea formation of 

 certain bacteria. 



In his Etudes sur la Here (Plate 1, Fig. 4) Pasteur described 

 bead-like chains of spherical organisms, which render wine, 

 beer, and wort so viscous that they can be drawn out into 

 threads ; this is caused by the formation of gum and mannite. 



Kramer has described Bacillus viscosus sacchari, which in 

 a short time converts neutral or slightly alkaline cane-sugar 

 solution into a tough mass of a gummy nature. He isolated 

 a Sac. viscosus vini (2 to 6 /x long), which was cultivated in 

 sterile wine, air being excluded. Sound wines infected with 

 this growth thickened in the course of six to eight weeks. 

 It grows best at 15- 18 C., and apparently cannot exist at 

 such a comparatively low temperature as 30 C. 



A mannite fermentation is sometimes associated with the 

 formation of slime in wine. The motionless bacterium isolated 

 by Gayon and Dubourg grows on the bottom as large zoogloea, 

 and thrives only in saccharine solutions. On the other hand, 

 a mannite fermentation investigated by Peglion in wine is 

 never accompanied by the formation of slime. 



A very comprehensive memoir regarding slime-forming 

 bacteria has been published by Kayser and Manceau. The 

 disease occurs especially in wines protected from the action 

 of the atmosphere. The formation of slime begins in the 

 lowest stratum of the liquid, and increases by degrees without 

 reaching the top. The disease occurs in those districts where it 

 is customary to remove the skins, stones, and stalks, before fer- 

 menting the juice. Such bright wines are usually poor in tannic 

 acid, nevertheless other wines comparatively rich in tannin may 

 be attacked. The percentage of alcohol and of free acid appears 

 to be of greater importance than the content of tannic acid. 



