928 
Journal of Agricultural Research 
Vol. V, No. 20 
like Streptococcus mesenterioides the naked modification—i. e., the form 
developed on a medium containing no sugar and having no capsule— 
succumbs more quickly as a result of desiccation than does the encap¬ 
sulated form. 5 . mesenterioides (13, p. 244) has been found to resist 
desiccation for a much longer period if developed on a saccharin medium 
than on one which contains no sugar. Revis (20) shows that two types 
of colon organisms which developed a mucilaginous type of growth were 
the ones which survived longest in soil. In another article (21) he sug¬ 
gests that the slime formed by organisms of the colon type may add 
to the water-absorbing and water-retaining capacity of the soil, and 
may therefore promote the longevity of that organism. Lohnis (15) 
says that not only the spores but also the bacteria with slimy walls 
endure the effects of desiccation very well. Lafar (13) emphasizes 
the importance of making a distinction between organisms like 5 . mesen¬ 
terioides , which surrounds itself with a gelatinous envelope, and organisms 
which carry on a slimy fermentation—i. e., conversion of sugar outside 
the cell into mucinous matter—without themselves being inclosed in 
capsules. Jensen (11, p. 323) uses the terms capsule formation and slimy 
fermentation interchangeably and regards the process as protecting the 
organism against desiccation. 
Buchanan (2, p. 378) offers a very comprehensive review of the litera¬ 
ture on the nature and morphological origin of bacterial slimes. Some 
describe gum formation as the result of a true fermentation of carbohy¬ 
drates by bacteria, calling it an extracellular synthesis, others calling it 
a true synthetic process, but not necessarily due to an extracellular fer¬ 
ment. Most of the bacterial gums reported in the literature are described 
as carbohydrates of • the formula (C 6 H l0 O 6 ) n . Bacterial slimes classed as 
dextrans are described by Brautigam, Kramer, Ritsert, Scheibler, and 
many others (2). Lipman, Greig-Smith, Maassen, and Laxa (2) found 
levulan to be the specific gum of several slime-forming bacteria. 
Schmidt-Muhlheim, Hueppe, Emmerling, Greig-Smith, Laurent, Ward, 
and Seiler (2) describe bacterial gums having the characteristics of galac- 
tans. A few nitrogenous bacterial gums are mentioned, but they appear 
to be less common than those of a carbohydrate nature. The protective 
action of these gums has been ascribed to their water-retaining capacity. 
Exclusive of organisms with such special protective structures as 
spores or capsules, it appears to be true that certain species are more 
resistant than others. Neisser (4) found that the organisms of typhoid 
fever and diphtheria were the most resistant; cholera, influenza, bubonic 
plague, and gonococci the least; and the pus-forming cocci, meningo¬ 
coccus, and tubercle bacillus of intermediate resistance. Briscoe (1) 
credits the tubercle bacillus with a greater resistance than most non- 
spore-bearing organisms. This power of resistance is no doubt due in 
part to the waxy or fatty substance found largely in the outer layer of 
the tubercle bacillus. 
