m 



96 



Streptobacterium plantarum (Table XXX a, b and c) most frequently forms pure inactive 

 lactic acid, but can also form dextro-lactic acid; in some few cases, indeed (Nos. P), 21, 31 

 and 32) even exclusively dextro-lactic acid. Though, like most strains isolated from pota- 

 toes, it forms much acid in milk, a powerful splitting of casein is nevertheless exceptional, 

 and has only been demonstrated in the two inulin-fermenting strains (Nos. 20 and 21) 

 which were isolated from cheese^). Nos. 2, 3 and 4 are slimy (ropy) in sugar agar, but 

 not in rhilk. Nos. 7 and 8 have at times shown some slime formation, especially in cane 

 sugar agar. Radiations from the agar stab are now and then seen, always in the case 

 of No, 11. 



As regards its relation to the sugars, Streptobacterium plantarum is affected to an 

 extremely high degree by the source of nitrogen employed. It is common, for instance 

 to find the fermentation of raffinose and inulin — and even of saccharose, mannite and 

 pentoses — fail with W as source of nitrogen. There are indeed some strains which can 

 hardly ferment monosaccharides (Nos. 24, 35 and the sour cabbage bacteria) unless 

 coaxed to a certain degree with their favourite dishes. With C as source of nitrogen it 

 prefers as a rule maltose and cane sugar to lactose, and often ferments raffinose, some 

 strains also inulin. The fermentation of sorbite and rhamnose is far more frequent than 

 in Sbm. casei^). A number of strains show a comparatively powerful fermentation of ara- 

 binose, and a few (as for instance most of those isolated from potatoes) of xylose. No. 1 

 can ferment a little starch. Briefly then, these bacteria can on the whole — as Was to be 

 expected of plant bacteria — utilise a far greater number of carbon sources than bacteria 

 living normally in milk, where there is no other source of carbon beyond lactose. 



From a morphological point of view, it will hardly be possible in all cases to decide 

 whether we are dealing with a strain of Sbm. casei or of Sbm. plantarum (PI. XLI — XLV). 

 In broth, Sbm. plantarum as a rule forms shorter chains, or even isolated long rods. If 

 they exceptionally form chains of small segments, then these latter are rounded, and 

 consequently much like streptococci in appearance (No. 44, PI. XLV). On solid sub- 

 strates, isolated rods, or a very few together will most frequently be found. 



') No. 1 has, however, formed a little inactive lactic acid from lævulose and saccharose. 



^) We have therefore doubted, if we should reckon these two strains to Sbm. casei or to Sbm. 

 plantarum, and only their powerful saccharose- and inulin-fermentation decided us for the latter. 



"l Several sorbite-fermenting strains of Sbm. plantarum (as for instance Nos. 19. 20 and 33) also 

 ferment some inosite, but only a trace of dulcite. 



