196 Studies m Bacteriosis 



RELATIONSHIP OF THE CAUSAL ORGANISM. 



Comparison of the above characters with those of other plant para- 

 sites leads to the conclusion that the organism here described is closel}' 

 related to, if not identical with, Bacillus lathyri found by Manns and 

 Taubenhaus (4) as the cause of diseases of the sweet pea, red clover and 

 soya bean, etc. A full description of this organism published by 

 Manns (3) shows close agreement with the above. Noteworthy points of 

 similarity are: (1) the morphology; the position of the flagella being 

 rather unusual for a bacillus, they are certainly peritrichous but there 

 is a marked tendency for those at the anterior end to be lacking in 

 stained preparations (see Fig. 5); (2) the butyrous and viscid growth 

 on most solid media; (3) the mucoid development in fluid media, 

 especially in Uschinsky solution; (4) the slow liquefaction of gelatine; 

 (5) the effect in litmus milk. Only two points of difference appear: 

 (1) in the resistance to heat; B. lathyri has a thermal death point of 

 48° C. and shows no growth at 37|° C. whereas the " Stripe " organism 

 has a thermal death point of 51° C. and does grow, though very 

 sparingly, at 37 — 38° C. It is quite conceivable that continued existence 

 at the temperature of the forcing house may have raised the heat- 

 resisting power of the strain; (2) in the power to reduce nitrates; 

 Manns found no reduction of nitrate by B. lathyri though in this 

 connection he states "Several of the strains produce nitrites from 

 peptone broth; thus in nitrate broth unless quantitative determination 

 is made for the nitrates placed therein one might easily assume nitrate 

 reduction." Special care was therefore exercised in determining the 

 reducing power of the "Stripe" organism. Pure strains from three 

 separate isolations of the organism were inoculated each into six tubes 

 of beef extract (" Jardox") with; and six tubes without, the addition of 

 1 per cent, potassium nitrate. After incubation for three days all the 

 eighteen tubes containing nitrate gave positive reactions for nitrite while 

 the eighteen controls without nitrate gave negative results. Nitrite was 

 shown by azo-colour formation in the sulphanilic acid + a naphthylaraine 

 reagent. This is a very delicate test for the presence of nitrite and is 

 probably more reliable than the method of determination of nitrate 

 adopted by Manns. 



The crucial test of identity will be the cross-inoculability of the 

 "Stripe" organism from the tomato to tlio sweet pea^. This has not 



^ In this connection it is noteworthy that Manns has isohited B. hilhyri from tomatoes 

 showing Blossom-End Hot and has been al)le to produce tlie synijiloms of this disease by 

 artificial infection i>f tomatoes with a strain of li. Idl/ii/ii isolateii from a species of Lathyrus. 



