SOLVENT ACTION OF BACTERIA—DESTRUCTION OF MIDDLE LAMELLA:—BACTERIAL 
SOLUTION OF CELL-WALLS—FERMENTATION OF CELLULOSE— 
DESTRUCTION OF WOOD. 
Next.to crushing and splitting, due to the rapid multiplication of the bacteria in closed 
spaces, solution of the middle lamellz uniting cell-walls is probably the most widespread and 
simple action of bacteria on plant tissues. This is common in a great number of diseases, 
but it is not always possible clearly to separate lysis from tension-splitting, when the bac- 
teria are multiplying rapidly in a given tissue and must have room. An excellent example 
of the separation of cells by a solvent action on the pectic matters composing the middle 
layers of the common wall may be seen in various rots of potato-tubers. A few days after 
an inoculation the tissue softens, and if it is then washed in water the cells float free, their 
starch content remaining unacted on (fig. 25). Potter asserts this solution to be due, in case 
of a turnip rot which he studied, 
to the presence of oxalic acid. 
The writer found oxalic acid had 
no solvent action on slices of 
turnip, but that ammonium oxa- 
late softened the middle lamelle 
decidedly. Inasmuch as a part at 
least of any oxalic acid liberated 
by any Schizomycete of this type 
would be converted into ammo- 
nium oxalate by the evolution of 
ammonia due to the continued 
growth of the organism, it is not 
unlikely that ammonium oxalate 
is the substance, which in some 
cases, dissolves the middle lamelle. 
It would seem, however, that 
Fig. 25 * in many cases a specific enzyme, a 
pectase, must be the solvent body. Vide paper by Spieckermann and papers by Jones. 
Once or twice in earlier papers the writer has used the word ‘‘cellulose’’ loosely, in the 
old way, for cell-wall, of which it forms, however, only a part. When the middle layers of 
pectic origin have been destroyed there yet remains a wall of cellulose surrounding each cell. 
Is this permeable to bacteria? Can any of the bacterial plant parasites dissolve it? No 
such crucial studies have been given to the subject as Omélianski, for instance, has given to 
the solvent action of the anaérobic organisms of marshes known as the methane bacteria. 
It has been demonstrated that the marsh-gas bacteria destroy cellulose in large quantities, 
but nothing like that, of course, occurs in the diseases in question. All we know definitely 
can be expressed in few words. 
Bacteria certainly find their way into the interior of cells which have not been crushed 
or mutilated. The evidence of this is the fact that they are so found in great numbers and 
inside cells under conditions which seem to preclude entrance through wounds of any sort. 
How do they enter? Their entrance is an extremely difficult thing to observe owing to their 
*Fic. 25.—Softened tissue from interior of a potato tuber inoculated with Bacillus phytophthorus and kept for 
6 daysatabout 25°C. Cells have separated, by solution of middle lamelle, but starch grains are intact. Oct. 26, 1906. 
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